/diy/ - Do It Yourself

>>829678
> ran out of solder
> bought "Bernzomatic lead free" solder from Home Depot
> doesn't work as good as 60-40 tin lead solder
> out of $8

Is there some trick to using this stuff or is half of everything that's enviro-friendly a hassle ?

>>829700

Don't buy solder form Home Depot. Also for lead free solder you need more heat

so why use 60/40 as opposed to 63/37?

>>829702
> Don't buy solder form Home Depot
I don't know. It doesn't scream low quality, rather it seems the lead free part is what is different.

>>829700
Does Home depot sell solder meant for electronics now, or are you trying to use the thick plumbing solder meant for blowtorches and big soldering guns.

>>829709
Often bit easier to get and does not behave that differently.

>mfw I found a nice stash of transistors, germanium ones even, like AD161 and AD162
DIY electronics: make an amplifier out of everything

>>829700
Someone on /diy/ or /g/ told me that lead solder is much easier to use. I bought radio shack 60/40 lead solder and it was a billion times easier for me to solder shit. Before that I'd only used lead-free, and made really shitty solder joints.

>>829724
> Does Home depot sell solder meant for electronics now
I think they always have. Yes. It's .060 lead free electrical solder near the propane torches made by Bernzomatic. A little thicker than typical electronics solder.
A lot of places carry electrical solder but it's always something weird made for a gorilla with a large soldering gun, never a nice little tube of Kester or something.

>>829762
https://www.amazon.com/gp/aw/d/B00GPZQ5B2/ref=aw_wl_ov_dp_1_3?colid=387FJF6O0WVS6&coliid=I2QN2RBJ7ZI8OC

Quick question here from an electronics newbie. Not much background except few higher-level high school classes awhile back.

So I'm planning on building a DIY Bartop Arcade Cabinet, using a Raspberry Pi 2 and RetroPie. To this aim, I scavenge a really old CRT monitor from my Dad's hoarding collection. Not being an /ohm/ guy, I really didn't want to mess around with any I ddin't know about, I was just looking to remove it from it's plastic housing and re-mount in the cabinet. When I did so, I only noticed after the fact that there were a couple lose parts to the setup and I'm not really sure what to do with them.

The first is a cable loop that obviously looks like it's supposed to go around the panel at some place. I tried fitting it on the very front, but it's a bit over-snug. I could probably get it on if it does indeed go there though.

The second is a random cable ending in some kind of loop connector at the end, this attaches to all the components at the very back of the monitor, where I assume the electron gun is or whatever. No idea where this goes. Based on my very limited knowledge of electronics, it seems like it's a ground maybe? The hole connector makes me think it was attached to the metal frame as a ground and it's lose now because I pulled the screws and washers out from the plastic frame/metal frame connection.

Haven't plugged it back in yet because I didn't want to mess anything up, does anyone think they can help me out?

>>829926

the loop thing is the degaussing coil. it's usually attached to the case so it surrounds the front part of the screen. the way you have it placed on the top pic is more or less where it goes - just wrap it around the metal band at the front of the tube.

the loose wire does look like a ground, it probably joins all the metalwork together, including that band I mentioned near the front of the tube.

just a progress report: I am the anon who bought a couple of the sainsmart 7" tft screens w/shield and arduino megas.

they work well, if you do these things:
1--you need to run them off external 5v power, not the arduino 5v pin. the screens flicker white if they don't get enough power
2--you need to use the SSD1963_800ALT driver in the hennings karlsen library, not the SSD1963_800 driver (the non-ALT driver flickers and is mirrored, the ALT driver works correct)
3--you need to calibrate each arduino/TFT touch screen separately, even if they are the exact same hardware: (--there is a sketch in the karlsen library to calibrate the utouch library for touch screens; it generates 3 sets of hex numbers that you edit into another file. Calibrate every separate arduino/touch screen setup you have, even if they are identical hardware,,,,,,, as the numbers it gives will not be the same for all--)

this also echoes what I said about sainsmart in the previous thread: their hardware USUALLY works right, but they don't give much help with the code.
I still have not gotten the 'documents' they mention on the product web page; I'll report back how useful they are if they arrive.

Also: people online several places mention they are surprised at how fast the 7" screen refreshes--and I would agree with that. It does look better than I'd expected.

I'm looking to wire a new CB and Scanner into my car's power. I just don't know the first thing about where or how to connect it.

A friend of mine who works for a local FD (and has more antennas on his van than I can count) recommended a couple pieces to the project.

>relay or center-off toggle to control the power to the radios either when the car is on or off.
>connect it to an unused fuse in the accessory box

I just don't know the logistics of where to splice the wires, what guage cable I should use, where to actually connect the power leads, etc.

Anyone have any recommendations?

Are there any good guides for setting up in-car Scanner systems?

I have an 06 Ford focus if it matters.

Hello hello electronics friends, I have a question.
I am acquiring electronic components at a fast rate, you know, salvaging and stuff. However I have a lot of different components, not just meme-resistors and meme caps, but all values
Categorizing these components would be essential. Do any of you guys use some kind of a database software to index your components (photographs attached if needed) ?

>>830005
>I just don't know the logistics of where to splice the wires, what guage cable I should use, where to actually connect the power leads, etc.

Wire thickness comes from the current the device draws. Going too big isn't a problem, but if you go too small they'll overheat and melt the insulation. Your equipment is probably a couple amps.

Using a relay like your friend recommended is unnecessary IMHO. I'm sure you can remember to shut the equipment off when you leave the car.

I'm assuming the parts are meant for a car, so you just need to connect them to the battery. There's probably a clearly labeled point for that under the dash.

>>830005
SSB CBs are normally fused at 4 amps.

AM CBs 2 amps.

Aussie / NZ UHF CBs 2 amps.

Scanners will be typically about an amp tops and probably less.

If your in some other country with something like pic related I'd suggest posting more details.

>>830061
I'll poke around. See if I can find the hookup.

>>830073
I'm in the US. Models are: Uniden BC15XT CB and BC355N Scanner.

speaking of wire thickness.

I am only a beginner and used 0.14mm for my direct current stuff (only very low current stuff like sinlge LEDs).

I've built an LED array for lighting the interior of a cabinet. 8 LEDs run parallel with a current of 400mA all in all. Do I need to step up my game concerning wire diameter?

>>830224
>he doesn't use 8 guage wire for everything

Is there any circuit made out of discrete components that can do this?

Basically taking a noisy signal from an antenna or sensor circuit (already properly amplified) and converting it into a clean square pulse so it can be used by a counter for example.
The point is every time a noise similar to that one appears a square pulse is created.

I don't care about overlapping,it is quite improbable that the events that cause those pulses repeat more than once every minute, and almost impossible after some seconds.

I was thinking about something like a time latch.

>>830285
retriggerable monostable?
there are a few different ways to achieve
typically used in switch debounce circuit if you are looking for search terms

>>830285
Monostable, pic related. Add an optional Schmitt trigger if needed.
Why does it need to be done using discretes?

>>830224
I'd use 0.14mm^2 for stuff under 1Amp. What kind of current source are you using?

>>830285
Use a monoflop. If you have a NE555 lying arround it will work too.

Forgive me for my english btw, I'm used to write in this language but not when it comes to technical stuff.

>>830292
>>830285
Didn't see the discrete part.

Do as >>830291 suggests.

>>830290
>>830292
Thanks guise
>>830291
Because with a uC I would just regurgitate the code, but I want to learn how to make analog things, an IC like the 555 like >>830292 said is fine too.

>>830292

3 AA batteries in series.

I'm fairly new to electronic through self study and a I have a few questions

1: can you use other components besides resistors such as a capacitor or even an led?
2:does the whole potential differences across resistances = supply voltage in a series circuit only apply to resistors or all forms of components in the circuit

>>830374
1: referring to voltage divider

Sorry I'm on mobile

>>830374
For 2, yes. Kirchhoffs voltage law always applies.


For 1, why would you want to make a voltage divider out of anything other than resistors? Excluding semiconductors that is.

Honestly though, I've never thought of it.


Actually, now that I think of it, with AC you can because everything is converted to impedance and what not. But that's called a filter.

>>82967

My turtle escaped while I was away in school. I'm back from the summer now and I'd very much like to recover it.

I was thinking of placing some bait and "watching" the area with a motion sensor connected to an arduino which would activate a camera, save the image, then email it to me whenever it detects motion.

Does this plan sound feasible? The only issue I have is will the PIR motion sensor not be able to detect the turtle since it is cold blooded? I know it works by detecting changes in infrared radiation (heat), which may not be as great compared to the changes when a dog passes by. I plan on using this sensor:
https://www.adafruit.com/products/189

I've also noticed a lot of cheaper arduino shields and components on eBay. Are those generally reliable? I mean if I can get the camera module for $10 as opposed to $37 from name brand sites I'll definitely do it.

Oh my gawd. Thank you for this thread. I have a very large project coming up. I just ordered some prototype boards for a circuit I made. It has about 50+ components and an arduino to boot.

While I've done some soldering before I've mainly just spliced wires or reapplied then to other electronic parts. I have 3 prototype board and I don't want to mess them up, can any one give me any tips or the correct way to solder or point me to videos?

>>829775
I have questions about this. I assume lead is bad (duh) but obviously I'm not inhaling it. Can some one confirm or speak on this?

As well, I assume I should get a new iron?

>>830488
SMD or THD? If SMD a hot air gun is your best friend, for THD or mixed any temp controlled soldering iron will be fine, just don't use a gorilla iron made for plumbing and you shouldn't have any issues, just follow basic soldering etiquette and use plenty of flux and keep your surfaces clean.

>>830488
Virtually no lead vaporizes at soldering temps. You still don't want to inhale the fumes from the burning flux though.

>>830374
1. Capacitive voltage dividers aren't that uncommon. Sometimes zener diodes are also connected in series to produce different voltages, but that's not really a voltage divider.
2. Yes, it does not matter what components there are.

>>830488
The primary risk with lead-containing solder is the rosin smoke. Inhaling smoke is bad for you. Lead-free solder isn't better in this respect.

>>830488
it's basically harmless at the amounts you'll be using.

that said, the smoke off some of the plumbers fluxes (grease, ammonium bifluoride, zinc chloride, hydrochloric acid) can be fucking brutal. stick to rosin flux or no-clean flux for electronics work.

>tfw no one responded

Thanks guys, I'm really excited.

>>830497
Thd! Not experienced enough for surface mount yet.

Got it, use lead solder, flux, and wear a mask. Still need to watch a video on it. I'll probably post some pics later.

Another thing, I was reading a link where someone made a circuit and when they were finished soldering they rinsed it over with soapy water. Um... I was under the assumption to not mix water and electronics lol how could they do that and what was the purpose?

>>830587
only if you have super sensitive shit like pressure sensors or LCD's does it matter, nothings going to be damaged from a few seconds contact with water. you want to assemble your board, then wash it, most manufacturers then say to bake at 100 deg C for 2hrs to completely dry it, but since you only have through hole stuff you can just use a hair dryer or leave it in the sun, if its particularly humid where you live or its raining you might want to do the final rise with deionized water, this will prevent any corrosion from occurring if it stays wet for a long time.

>>830587
If their solder used water-soluble flux, then water was the correct solvent. Alcohol (ethanol or isopropanol) is also often used in washing PCBs.
Water wash does not damage normal components or PCBs as long as you let them dry completely before applying voltage.
Some shit like switches, buzzers etc. don't like washing at all, because water/alcohol gets inside them and won't come out easily.

>>830587
>not mix water and electronics

Its most important not to mix wile they are powered up. I've seen TO220 devices with the legs totally eaten through after spending a day powered up in a river.

hello /diy/
I need help with an Electric Circuit.

I need the equations for the first and second Kirchoff's laws for circuits.

Pic related it is the circuit .

My project is due tomorrow and I need the equations in order to make a fortran program to calculate I1, I2 and I3
R - Resistance in Ohms
R1=1 Ohm
R2=1 Ohms
R3=2 Ohm
R4=1 Ohm
R5=2 Ohms
R6=4 Ohms

E - voltage in Volts
E1=23 V
E2=29 V

>>830620
>I need the equations for the first and second Kirchoff's laws for circuits.

You know you could have just typed, "kirchoffs circuit laws" in google instead of writing out this long post and taking a picture, right?

>>830620
consider chosing a ground.

>>830622
I know what the laws are man

I just can't solve the problem.

>>830626

It is a theoretical circuit.

>>830628
do mesh current analysis and you get: I1=3, I2=5, I3=1, the equations are difficult but not for a computer. Takes about 10 minutes.

>>830629
also the currents add in the middle so your current path is wrong for one of the loops.

>>830630
anyway the easiest way to do this is when you have a voltage source, draw your current loops so that they have the same behavior (e.g. making all the voltage sources drops) this makes your analysis easier.

just did it in orcad to verifiy, hope this helps.

>>830620
>he can't do basic circuit analysis

R1*I1 + R3*(I1-I2) + R4*(I1-I3) - E1 =0
R2*I2 + E2 + R5*(I2-I3) + R3(I2-I1) =0
R4*(I3-I1) + R5*(I3-I2) + R6*I3 = 0


? thanks to /adv/

>>830620
Not to sound rude but this is really something you should figure out yourself. It's a really basic concept. Unfortunately, if you can't figure this out then maybe electronics just isn't for you.

That's perfectly fine, not everyone is good at everything. This hobby and even the engineering field is 80% figuring out stuff on your own. A basic google search for KCL or mesh analysis would've given you the answer. If a Google search is too much to ask, then I suggest looking for a new hobby/profession.

update on sainsmart documents: it's just the henning karlsen files, sort of....

the files they sent was two zips.
one just has some PDF data sheets and schematics in it, not useful unless you had to write your own drivers from scratch (or were connecting the screen directly without the TFT shield)
the other is a weird partial version of the karlsen files. the top level has the UTFT and Utouch folders, but all of the examples are not included in each. And there is another UTFT folder inside the Utouch folder, that doesn't appear to get referenced at all? The only sketch inside the utouch folder is the calibration sketch. .....so in other words: don't bother with asking for the sainsmart documents.

on the sainmart web page for the 7" tft screen, there is 4 links to support files:
one of them asks for a username and password, so I dunno what that file is
two of them are zips but they are corrupted or in a non-standard format... I have the current versions of winzip and winrar and neither will work.
the fourth file "51_test_program_keil_project" has a bunch of files but I dunno what they do? there's no ino files, but a lot of cpp and obj files. Obviously for another IDE but I don't recognize it.

semi-related: as of late-2013, Mr Karlsen did not seem to hold a high opinion of the Sainsmart products -- (posting here as doc_norway) -- http://forum.arduino.cc/index.php?topic=198188.0
only 126 posts there tho, prolly not his usual hangout

> If a Google search is too much to ask, then I suggest looking for a new hobby/profession.

this is just pure nonsense. in the real world, you never ever have to do this kind of analysis, in the same way you never have to find the cotangent of an angle, or the area of a rhombus. these are just hurdles they make you jump in order to get a piece of paper. it's certainly possible to enjoy the hobby with no more theoretical knowledge than omh's law.

> If a Google search is too much to ask, then I suggest looking for a new hobby/profession.

this is just pure nonsense. in the real world, you never ever have to do this kind of analysis, in the same way you never have to find the cotangent of an angle, or the area of a rhombus. these are just hurdles they make you jump in order to get a piece of paper. it's certainly possible to enjoy the hobby with no more theoretical knowledge than ohm's law.

>>830694
I wouldn't say it's nonsense. That stuff, like lots of college stuff, is supposed to give you better understanding of the underlying principles.
I agree that lots of it is rather useless in real life, even for engineers.

>>830694
>an electrical engineer will never analyze a circuit

Kek

>>830749
Manually, using that method? Not very likely.

>>830751
That circuit is so basic that by the time you built it and simulated it on your computer you could have done it by hand three times

sainsmart 7" touch screen update #3....
the arduino is run off of a separate 5v power supply that uses a y-cable to split power between the arduino barrel jack and the screen's own 5v inputs.

I have noticed that if I leave the arduino connected to the PC, after 10-12 times of re-loading a sketch + rebooting,,,,,,,, the touch screen stops responding.
EVERYTHING ELSE keeps working like it should, but the touch screen simply stops indicating it has any touch data. myTouch.dataAvailable() always returns false.

The only way to get it working again is to disconnect the USB cable, and then turn the arduino's own power off and back on.

This has drove me nuts for two days,,,, I'd change some tiny bit of code--not even involving any of the utouch functions--and suddenly none of the touch screen input would work.

> That circuit is so basic that by the time you built it and simulated it on your computer you could have done it by hand three times

that's kind of the point I was making. real world circuits that engineers work on do real things like measure your heart rate or keep you cool. they are too complicated to analyze formally, and so no analysis is ever done except in rare places such as component manufacturers. the same is true in programming: there are analytical methods to prove the correctness of a program, but no-one does it for real coz it's so complicated an time-consuming.

it's harsh to realize all that time you spent banging your head against the wall trying to understand theory was wasted, but that's how it goes.

>>830764
It is also very artificial and if you add anything interesting to it, you can't solve it with that simple method.

https://www.youtube.com/watch?v=GBuTiCdHiWE

Has anyone here tried stuff like this? Does it work? Is it permanent? Seems like black magic to me.

This is my first PCB design. How bad did I fuck up?
It's supposed to be a breakout board for an lpc812 with 5v regulator, 4 open drain outputs and 4 protected (led + resistor) inputs. The resistors and diodes (I used the same symbol because there isn't one for an led) are 805s, the IC is an so-20 and the regulator and FETs are sot23-3s.
Also why is fritzing such a laggy piece of shit?

>>830834
holy shit where to begin?
the top row of pads aren't even aligned. are they supposed to be?
there are at least two traces on the top row (pads 2 and 8 from the left) that are too close or touching other pads
i don't think your switch is the right way around but im willing to be corrected on that
avoid acute angles on traces, they act as an acid trap and cause problems during manufacture. ideally avoid 90 degree angles also.
have you enabled DRC (design rules) based on where you are getting it fabbed?
do you really need a double sided board? i bet you could tidy it up and fit everything neatly on one side.
it looks like you might have some fucked up pads and vias lower left, between q2 and q3 labels

so in summary its fucking ugly as shit but it might work.

>>830690
you want the keil project, that will have example code and the driver, you're going to have to adapt the driver and example cpp to arduino shit if you want to use it on anything other than the MCU they wrote the example for. the key thing you want to pay attention to is the initialization code, make sure you refactor the delay commands correctly, i.e. they might have a Delay(int uS) which maps to the arduino's Delay(int ms) fine, but are completely different time bases.

also:
>PDF data sheets and schematics in it, not useful
lrn2read

>>830834
>part 1 has a short
>sink screen over pads means its unsolderable, the sink screen will just burn and destroy the pad surface
>no clearance between your main IC and header plastic, use a different connector or move it much further away
>same deal with those trannys at the bottom

honestly how the whole thing isn't red with DRC errors is outstanding, stop using that shit software, altium recently put out a free version of there tool called circuitmaker, the only down side is its cloud based cancer so if you live in a shit hole with no internet its just not going to work.

>>830834

Fritzing is at best a crude circuit diagram builder; it really really struggles with building actual boards. While it'll be much more complex to start on another software, your final result will actually be something that will work unless you truly fuck something up; design rule checks will keep things in shape, where in Fritzing it kinda does whatever.

>>830809
Actually it'd just as easy. KCL and KVL always apply no matter what the load is and they're very easy concepts to grasp.

>>830834
Ugh, Fritzing should stick to breadboards.

Redo it in KiCAD and come back.

I don't understand BJT at all. I've been reading and watching videos and tinkering but I still can't wrap my head around pic related.

This was a schematic I aquired for switching the high side of a nixie tube using a 16 bit shift register current sink IC. the transistors used are MPSA42 and MPSA92, respectively, but I don't understand why the NPN needs to be there, or why there is that voltage divider (I assume) on the bottom left.

If someone could give me a pointer or at least a resource I could use to help me understand it that would be fantastic.

>>830931
When the current sink is off, the emitter of the NPN sits at 5V, V_BE = 0 so the transistor is off. The 1 Mohm resistor pulls the PNP off.

When the current sink is on, the current sink pin will be at ~1V, the 82k resistor gets some current across it, V_BE = 0.7, the 1Mohm resistor has current across it, turns the PNP on.

You need the NPN because otherwise the LED driver is exposed to 180V. The question mark resistor provides bias for the current sink output.

>>830924
Yes, they are. They're useful even after school. However, the problem in question looked more like a loop current or node voltage method homework to me.

>>830931
The mystery resistor is there to guarantee that the output leakage current of the driver won't turn the NPN on.
NPN is there, because your IC can't handle 180V. With that transistor, the highest voltage it'll see is 5V, since the NPN turns off if its emitter voltage tries to rise above 5V-0.6V. The lowest voltage you'll see on PNP's base is 180V-0.6V (nixie on).

>>830931
The NPN is being used in common-base configuration, which is a little unusual, but it makes sense here. Like other anon says, its purpose is to shield the stuff in the lower-left from the 180v.

The driver pulls a certain amount of current out of the emitter of the NPN. The transistor allows most of that current (β/(β+1) of it) to come from its collector, and the rest comes from its base. So it's acting as an "amplifier" with a current gain of slightly less than 1, essentially no current gain that is, but a voltage gain that depends on how the circuit connected to its collector behaves. That's dominated by emitter-base junction of the PNP.

The 82kΩ resistor is there to limit the amount of current that the 6276 pulls. Otherwise there would be a near-short-circuit from the base of the NPN to ground via the 6276, and something would go pop.

The PNP is acting as a common-emitter amplifier, which you've probably seen before.

The 27kΩ is probably the "ballast" for the nixie; gas tubes will take all the current they can (they have a negative-resistance characteristic) so you need to have a resistor or something in there to protect them. Though in this circuit it looks like the PNP might be limiting the nixie current, I dunno.

[continued in next comment]

>>830946

So, putting this together: when the 6276 turns on (connects to ground), the base-emitter junction of the NPN starts conducting. The amount of current is (5v minus Vbe minus 6276's voltage)/82kΩ, which I'm going to wild-guess is around 45µA. Approximately that same current gets pulled through the base of the PNP (at first, it comes from the 1MΩ resistor, but once the base drops more than a volt or so the PNP turns on and supplies the rest). Assuming the PNP has a β of around 100, this means about 4mA is available to flow out of the PNP's collector, through the resistor, and to the nixie.

That actually seems a little weird to me: if I were designing it I'd make the 82kΩ resistor a little smaller, so that the nixie's current is limited by the ballast resistor and not by the PNP, since transistor β isn't super precise. Maybe there's enough voltage drop in the tube itself that it works out anyway.

>>830488

Lead solder is slightly easier to use (melts a bit easier). Some of the silver-based solders are almost as easy, though, and in hobbyist amounts the extra cost is small.

As for lead toxicity, just set aside an area dedicated to soldering, never eat in that area, and wash your hands afterwards every time. Just like you would with any other toxic stuff. It's not gonna kill you dead, you could probably lick the solder regularly and not have any visible ill effects for a long time, but lead poisoning is cumulative and affects your brain, don't mess with it.

>>830936
>>830939
>>830947
Thanks very much anons, I'm not sure I understand all that's been said but I have a much clearer understanding of what's going on.

For now, I can't quite get my head around what is happening to reduce the voltage on the emitter side of the NPN. I was under the impression that if the collector was at 179.4V(from the V_BE drop of the PNP), then the emitter would be at or very close to this voltage if the NPN is used at saturation as a switch. However, this doesn't seem to be the case, instead it is reduced to 5V (either by the limiting of the base voltage, or by some effect of the 5V source on the far left, I am not sure).

I am also unsure of >>830936 's comment about the voltage of the current sink pin being ~1V when switched on. >>830939 's mention of output current leakage is weird to me for the same reason.

Finally, I am not certain what is meant by the "biasing" effect of the mystery resistor.

Cheers guys.

>>830947
The nixie tube voltage drop is something like 100V or more, so the resistor sets the current if transistor's gain is what you assumed.
The guaranteed gain of MPSA92 is only 25, though.

>>830950
>if the NPN is used at saturation as a switch
Yes, it's not a switch. It's operating in its linear region.
You can think it this way: for the transistor to conduct, the emitter voltage must be less than the base voltage. So, the current through the 82k resistor is limited to current which is enough to raise the emitter voltage to 5V-0.6V. Assuming your driver pulls it's output to precisely 0, the current is then 4.4V/82k. Transistor burns around 180V-5V.

>mention of output current leakage is weird to me
The datasheet of your IC says that the outputs can sink at most 5uA when off. PNP's base would get bit over 4uA and assuming a gain of 100, it would leak around 0.4mA to nixies.
Mystery resistor is chosen so that 5uA isn't enough to pull the voltage low enough for the NPN to conduct. A simplistic way to calculate it would be 0.6V/5uA=120k. In reality you need smaller resistor, because Vbe isn't fixed 0.6V.

>>830939
KVL is an integral part of mesh analysis and KCL is an integral part of node analysis, so yeah the homework posted would be easily solved with mesh and it is something electrical engineers actually use in the field to save time.
Granted, I typically use nodal since it's usually faster in my erperience as far as real world application goes. This problem seems designed for mesh though.

>>829775
Lead free solder is total shit and only used because the fags in the EU wanted to take lead out of everything because they thought having it in electronics was harmful to health which was really just a ploy to keep american competition out of their market which failed miserably for them.

There's literally no reason to use lead free solder unless you're trying to sell what you're making in Europe.

>>831027
Lead free solder is also much more expensive than lead solder with no discernable benefits. Most serious solder users prefer to use lead based solder when possible.

>>830950
>voltage of the current sink pin being ~1V
The datasheet gives the voltage as 0.7 V, I don't know what it would be in reality.

Mystery resistor provides a path to +5V when the current sink is off. Maybe biasing isn't the right description for this case. Anon's point about leakage is a good one.

>>830939
Nodal and mesh analysis are literally applications of KVL/KCL. Idk what you're even trying to say with that.

>>831111
They're easy-to-computerize algorithms which are based on KCL/KVL and Ohm's law. Before teaching you node/mesh analysis, you were taught a bunch of other ways to solve similar problems (which were also based on KCL/KVL/Ohm's law).
What I'm trying to say that situations where a) the simpler methods aren't sufficient or are more tedious to apply and b) the problem is solvable using node/mesh analysis on paper and c) it makes sense to solve the problem manually are rare. Compared to that, the emphasis on teaching node/mesh analysis is totally disproportionate.

Well, I guess it made much more sense in the eighties and earlier.

I like to do vintage electronic repair and homebrew stuff like N8VEM but I never really stockpiled parts like caps and resistors, so now that unis out and I can't nick parts from the EE lab where can I buy sets of just random things I'll probably need?

It hit me really hard when I was repairing this old calculator and I realized it had a bad cap and I thought "oh I'll just go get one tom- oh right"

I'd rather not wait to order parts after I realize I need them. I could go to my local electronics store but it's still drastically over-priced to do that on a per part basis, particularly since I hope to get more serious about the hobby.

>>831196

>>831198
Damn, and I just wasted a $50 amazon card I got for my birthday on a motherboard from 1999 and a label maker.

Appreciate that though that's exactly what I meant.

Is there one for common TTL stuff or one for common processors?

this might be the wrong thread to ask but: does anyone here have experience with Microwave office (previously owned by AWR no owned by NI) more specifically does anyone have experience with nonlinear inductor model(s) they have on their ??

>TL;DR how does one use non-linear inductor models in microwave office

Is it safe to use to use one of these b2 connectors on live wires? Got two live ac wires I have no idea how to disconnect, so put two of these on them for now.

>>831217

what exactly are you working on that is AC and can't be disconnected.

Is there anything wrong with plugging in several usb chargers at once, and hooking up their outputs in parallel to provide 5v at a higher amperage than each could do on its own?

Or a 12v and a 5v psu, only connected at output ground but providing the voltages to the same project?

>>831231
Connecting voltage sources in parallel like that doesn't really work. There's a slight difference in the voltage between them and the highest one will be the only one to provide current. It works with batteries because they balance each other due to internal resistance.

The current draw of your USB device is controlled internally anyway. It won't draw more than it's designed to just because it's available.

>>831236
what about the second scenario?

>>831238
> Or a 12v and a 5v psu, only connected at output ground but providing the voltages to the same project?

You mean connecting the 12v and 5v rails? That's just going to kill the PSU and your USB device.

Using just the 5v output will work and provide ten amps or more. It's still not going to charge things super fast. A 10A power supply CAN supply 10A to a load, that doesn't mean it has to; current draw is set by the load not the source.

If a phone's internal charge circuitry is set for a max of 1A it will pull 1A from a 10A supply. The wall chargers they come from are always sized to match the phone.

>>831227
It's my home security system, after a power outage it kinda messed up and went into armed mode, since I didn't have the code for it I had to turn it off. Anyway it's connected to the distribution board and I don't know which circuit breaker turns it off.

>>831217
It some wire that's connected to the house's electric panel and I don't know which switch turns it off.

>>831254
meant to quote:
>>831227

>>831254
Why can't you switch them off until you find the right one?

>>830954
Thanks very much Anon! I think I am almost there in terms of understand the whole circuit.

The last question (I hope) that I have is about the voltage at the emitter - I understand that when the sink is off, the voltage at the emitter is too high to allow a current through the BE junction. However, I don't understand how the 5V source on the left creates that voltage through the resistors. Does the voltage just ignore the resistance since no current is actually flowing? Maybe this is a very basic aspect of electronics I am missing, but it sure has got me puzzled.

>>831289
Here's a thought experiment for you. You have a +5V source and a 10k resistor. One end of the resistor is connected to +5V, the other end is floating. What's the voltage on the floating end?

>>831294
My thinking is that it's gotta be 5V, but as soon as you try to measure it with a voltmeter you put it in a circuit and it would in almost all circumstances give a non-5V reading. I presume this answer has got to be 5V, but I don't really get how that works seeing as it seems to literally just be the potential difference, as connecting it to anything would actually change the voltage at that point.

>>831299
Let's say the voltmeter has a 10 Mohm resistance. What's the voltage?

>>831302
It'll be like 4.995V, so pretty much 5V. So, floating points in a circuit are at the same voltage as the nearest voltage source, even if there is a resistor before the voltage source.

I can get my head around that, but doesn't the emitter of the PNP also have it's own non-5V voltage because of the 5V at the other end of the BE junction?

>>831314
You mean the NPN? The BE junction is not going to conduct appreciably until you put 0.6V across it.

Does anyone know how to simulate a circuit with a CdS cell / light bulb feedback loop? I'm using QUCS, but I'll use anything else that's free if I need to.

>>831334
Make a negative resistance subcircuit?

>>831245
no no, just the ground but both powering different voltage requirements of the same project

actually I just did it and it worked fine.

Can I use regular ceramic 1000VDC rated caps as Y1 caps in a power supply?

For example, these are datasheets in PDF for the caps in comparison:
1000VDC ceramic
http://store.comet.bg/download-
file.php?id=1726
400VAC Y1 cap
http://store.comet.bg/download-file.php?id=1618

What is the worst that can happen? Also what does /diy/ think about X and Y caps, I think I know the theory (they are supposed to filter out inductive loads from the grid) but how important is it in practice?

For example, PSU causes interference with TV and lights in the room and such?

>>831334
Make a voltage controlled resistor, run the control voltage through some suitable non-linearizing circuit to model lamp/CdS cell nonlinearity?

http://www.ecircuitcenter.com/Circuits/vc_resistor1/vc_resistor1.htm

>>831373
Depends on your definition of "can".
X and Y capacitors are safety rated. They're guaranteed to withstand several times higher voltages than their nominal rating is (much more than 1kV for 400VAC capacitor) and they're meant to fail in a safe way.
Your random 1kV ceramic capacitor will do the filtering job just fine, but you have no guarantees about safety. The worst thing to happen is that you kill someone when your capacitor fails.

Does anyone have an ebook version of Art of Electronics 3rd version? I can only find crappy scans of the 2nd.

>>831325
I did mean the NPN and I think I understand... Even though there is 5V at the Base, and the BE only requires 0.6V to begin conducting, it literally cannot act as a conductor until the current flows (which it can't), hence there isn't a 4.4v at the emitter.

Thanks very much for all your help, Anon, I think I'm really getting it!

>>829678
I fucked up. I deep discharged a pair of SLA batteries. I know repeated deep discharges will cause them to go potato, but is there a way to revive them from this? How would one go about such an operation?

pls. I don't want to eat $40.

>>831409
Me again.
Alright, just for the archives: If your 'smart charger' is too smart to save your job, run some current into the cells. You have to get them high enough for the charger to recognize the batteries. 12v SLAs charge at 13.5v. Charge them enough for the robot to take over.

I'm in the process of making a refurbished VFD clock. I'll be driving the thing with an Atmega328. As you might know the Atmega runs on 5 volts, but the display needs 12 volts. I was thinking about adding a shitload of transistors, one for each pin, but I don't know if there's a better and cheaper way to do this. Maybe an IC with a bunch of transistors inside it?

In case I couldn't find a good IC or similar, would the 2n3904 would be a good option?

>>831443
It doesn't "need" 12v. You can run them with a AAA and a 9V, AAA for the element and 9V for the grid and anode. Try using 5V and see what happens. Be sure to check current.

>>831446
5 volts aren't enough to drive a vacuum fluorescent display, at least not this one since it's quite big, that's why I need something to do the switching, to send 12v into the display. I'm fully aware of how this displays work, this is a test I did some months ago:
https://www.youtube.com/watch?v=h5IeW_Lv75Y
I will power the thing with a 12v wall wart, and maybe a Lithium battery with a step up converter if I want to make a portable version. The only thing I need to know is what would be the best way to do the switching, individual transistors would be very bulky and probably relatively expensive, that's why I was looking for an IC or something that can do the switching in a compact space and without >9000 circuit traces.

I made a drawing, sorry about the quality.

>>831462
Digikey has some VFD drivers, and they have a few through-hole parts available. May want to look at that
http://www.digikey.com/product-search/en?pv38=55&FV=fff40027%2Cfff8020a&mnonly=0&newproducts=0&ColumnSort=100001&page=1&k=&filterAlwaysExpand=1&quantity=0&ptm=0&fid=0&pageSize=100&akamai-feo=off

>>831027
Lead free solder was implemented to protect waste disposal and recycling workers from lead exposure.

A large part of our e-waste is exported to developing countries where worker protection devices such as respiratory masks or a well ventilated work area are not implemented, also worker hygiene is not up to standard.

Parts that cannot be sold are mostly burned so lead poisoning from these fumes are, or were, common.

Sup /ohm/, I accidentally a trap.

TL;DR, I need to store up to 32 bytes in such a manner that I can scroll and replay them at will, without a uC. Halp?

Ok, so long story is pic related, a toy which will let me do the above, store and recall 32 bytes of data in 8 bit blocks. Idea is I can select bytes and write bits using the switches, then run or step through the sequences later. This will be a neat and useful toy for other hardware dev needs, and seems like a fun way to learn some new shit, but here's the trap. Using 32 8 bit registers seems excessive, but I have no idea how to do 32 bytes of memory otherwise, and I'm not sure how to glue the memory in. Halp?

>>831467
>>831468
Thanks, I'll see what they've got at my local store first.

>>831497

one good way to simulate memory is with memory. like pic related. use a counter like a 4040 to step through the lower 32 bytes (5-bit address bus) and connect the 8 switches to the data lines.

>>831502
Using memory.. as memory, fascinating anon!

No really, my google-fu clearly failed, I was looking for "32 byte RAM", i was trying to find the smallest memory chip available but clearly failed. That's a solid start. My next possible catch was devising a way to recall each byte when the device is in play mode and I am stepping through addresses. My idea was to run the display output through some 74HC147's, then use the combined 8 bit output to reliably recall a specific memory address, In effect, assigning a memory address to a digit on the display. Does this seem legit?

>>831535
>How about a nice game of chess?

>>831529
Do it like this anon. The hard part is wiring it all up. You'll need some sort of 2 digit 7 segment driver, or a binary to BCD converter.

>>829678
https://www.youtube.com/watch?v=mXli8ylucBg

This seems like an appropriate place to ask.

I want to generate power while riding my bike. Nothing too extreme, but enough to charge a 2.4v 450mAh Nimh battery.

With what I have pictured, there's a peak of about 100v but almost no current.

Realistically, how large a coil and magnet would I need to reach my goal?
Does the ferrite rod help or hurt my cause?
Any links to previous experiments like this with successful results are appreciated, thanks guys.

>>831764

there's this old-school thing called a bike dynamo that does what you want very well. alternately, you could install an old-school mechanical speedometer that transfers rotations from the wheel to a spinning shaft on the handlebars. attach a small DC motor to this shaft and you have a ghetto generator.

>>831764
Just remember, this will make your bike a bit harder to peddle, no matter how you do it.

>>831764
Use about 200 turns of fine insulated wire and a proper neo magnet

harddrive magnets aren't the best for that stuff.

put multiple magents around the rim to balance it better during high speed rotation.

use a capacitor to store the charge and some method of electronics (too advanced for me) to deliver a steady supply of power to your device

>>831534
>>831535
> needs more blinkenlichten

I assume your intention was to nudge me off to the schematics for these things to see how they do it, an avenue I had not even considered. Cheers.

>>831716
That's.. pretty close to what I had in mind, except I had the output of the display driver talking directly to the "memory controller" (whatever that ends up being) instead of splitting the counter output. Thanks for going to the effort of a block diagram man, I owe you an alcohol.

How much of a money investment do I have to expect to get in to electronics? I'm a broke nigga but I've been wanting to get in to it for awhile. How cheaply can I do it?

>>831790
I figured. I'm on that Physics-101 high.

>>831793
At what gauge would the wire start getting hot? Never?
That sounds like the voltage would be extremely high, too.

So I'm guessing I should keep the ferrite?

>>831851
40€ a month should be more than enough to buy all the components you need on a monthly basis unless you buy from rip off suppliers who charge $1 for a 555 chip.
You'll have to make an initial investment for the tools and indispensable components though.
-Soldering iron
-Multimeter
-Some cheap components to make a broke ass PSU
http://www.instructables.com/id/Fully-adjustable-double-output-power-supply/
-Desoldering pen
-Resistor and capacitor kits
-etc

>>831866
I was moreso wondering of the cost of the initial investment. How much will all of that probably cost?

If you're a broke ass nigga in the city, there's bound to be thousands of junked electronics in a dumpster near you.

>>831868
-Soldering iron: around 20€ if you want a decent one like a velleman
-Solder: around 10€ for a good roll
-Multimeter: I recommend to buy 6€ chinese crap until you learn how not to break them and move to a better one.
-Some cheap components to make a broke ass PSU: I used wall warts until I made it, so basically 0€. Making one like this will cost you around 20-30€
http://www.instructables.com/id/Fully-adjustable-double-output-power-supply/
-Desoldering pen : 2€
-Resistor and capacitor kits 10-20€?
-Maybe add 30€ more to buy all the other things you'll need, like wire clippers, helping hands,...
>>831873
This is a good way to start, just don't kill yourself with charged capacitors.

>>831878
Thanks!

>>831878
>This is a good way to start, just don't kill yourself with charged capacitors.
Hey, you wanna hear a funny story about a 15 year old and an old Dell CRT?

I'm a bit confused by op-amps. If I wanted to take 12VDC coming from my car battery and crank it up to 60V is it just as simple as pic related?

In doing further reading I'm getting the impression that an op-amp can't boost voltage beyond what's coming in via the supply rails? So if my supply is only 12V I can only boost close to 12V then? Not to 60V, right?

>>831893
> I can only boost close to 12V then? Not to 60V, right?
Yes.

OP amps are for amplifying signals. It's completely the wrong component for your purpose. You need a step up buck converter.

>>831896
Ah, I see. Thanks for the info. I'll look into it. I'm a little new to electronics.

>>831893
do a google search for "Cockcroft–Walton generator" or "Greinacher doppler" (they are basically the same).
You will be able to increase your voltage (theoretically as high as you want, in praxis i would stop at 3-4 multiplications)
but you won't get much current.
Or to put it another way voltage will drop rapidly if you draw to much current.

>>831896
A step-up buck? You mean a boost?
Or we may have different terminology, but I and everyone I have ever worked with have always called a chip that regulates the input to a lesser voltage a buck or step-down, and one that regulates to a higher voltage a bost or step-up.

>>831924
>step-up buck? You mean a boost?
Different words for the same thing.
buck = step down buck
buck boost = step up buck

Just got myself a new toy. Now that I have a job I figure I can finally afford this, but since I have a job I will have no time or energy to do anything with it.

>>831930
Buck-boost refers to the inverting configuration and "buck" isn't some generic term for a switcher.

>>831931
Mirin

>>830849
>you want the keil project, that will have example code and the driver, you're going to have to adapt the driver and example cpp to arduino shit if you want to use it on anything other than the MCU they wrote the example for.
why do I need the keil project files? what does it do?
and I assume it must be opened in amtel studio?

the filenames don't appear to be English based at at least one cpp file references the Chinese font file. I didn't know what IDE to use and I can't read Chinese anyway.

>also:
>>PDF data sheets and schematics in it, not useful
>lrn2read
yea, but you see,,, if you use the tft interface shield and the hennings karlsen library, then the karlsen examples already work. there's not much point in reading through the data sheets and schematics.

sanity check /ohm/.

I want to make a dual rail benchtop PSU. I can just do pic related with a circuit matching the characteristics i want and not have anything blow anything up, right?

I bought a 1 dollar DIY kit for blinking lights from ebay to try my hand at soldering. Any obvious rookie mistakes you can see on the photo?

>>832031
>from left to right, top to bottom
Possible cold joints at points 4, 7, and 15. Is that a hair or a scratch at the top left? You laid the solder on a little heavy all-around, and it needs clipped. Not bad for rookie soldering though. If it doesn't work I'd reflow the possible cold joints first, then do some cleanup to make sure there aren't any little bridges getting through the resist into the wrong traces.

>>832031
Some joints look cool like >>832046 said.

I suspect that you didn't do them in 'one stroke'

>>832046
>>832047

Yep, that's dog hair. All the cold joints you mentioned happened when i used thicker solder I got from my friend before I found mine. It's on the right, compared to my 1mm one. And on the good joints I put solder until I saw that the whole pad is covered, is that not how it's supposed to be? And yeah, it works.

>>832004

yeah, it looks like a fine circuit. I like the way they biased the ADJ pins so they're 1.2V below ground. this lets the output voltage go all the way to zero instead of the usual minimum of 1.25V.

Hi /diy/ simple but strange question here.
I have this IRF540N mosfet which is switching a 330R and a green LED, the thing is, if the resistor and LED are before the mosfet (this means they're connected to the drain) the current is 29.3mA. But if the mosfet is moved and now the load is connected to the source the current drops to 19.9mA.
What is this sorcery? Aren't both circuits supposedly equivalent?

>>832277
Connected the other way around.

>>832279
I forgot to connect it, but you get the idea.

>>832277
I'm not sure which configurations you're talking about, but here are 3 that sound like you're describing.

The current in A will be less than B because transistors are not perfect conductors even when on. You can find this in the datasheet as "on resistance" but it depends on multiple factors, primarily the gate voltage. Transistors aren't really switches but more like variable resistors.

The current in C will be less than B because the transistor is in a common drain configuration instead of a common source. Remember that the voltage which turns on the transistor is the difference between the gate and source. In A and B the source is always at 0 volts and the gate is always at Vcc, so it has the maximum voltage. In C the source voltage is going to be more than 0 because it has things in between it and ground. Since the difference is less (gate - source) the transistor will not be on all the way. I expect you're confused because you think when things are in series their order doesn't matter. The problem is they aren't really in series because the gate is not connected in series with the LED and resistor.

>>832290
Thanks for the explanation, I'll use A from now on. I've made a test and the A connection draws as much current as short circuiting the mosfet, so that's good enough.

>>832004
How can this be a 0-60V power supply?
The rectifier output is only 48 volts.

>The rectifier output is only 48 volts

seems we had this misunderstanding earlier. see >>831214 for diff between RMS and DC.

>>830834
You are the reason everyone shits on fritzing. Use a proper tool (kiCad), and learn the basics.

I plan to make a hand crank generator for my phone. Should I make my own circuit, or should I connect the generator straight to my phone's charger?

> should I connect the generator straight to my phone's charger?

definitely not. the charger contains a feedback loop (from the secondary to the primary) to set the correct output voltage. if you just attach a voltage to the secondary, it will not have any way of regulating that voltage. so, you need to provide rectifying, smoothing, voltage regulation and maybe current limiting all on your oddy-knocky.

>>832432
I thought of using a series of simple motors, the ones you find in a rc toy. They output DC, right? I won't need a rectifier then. I was thinking of a voltage regulator and a diode. Wouldn't that do the job?

>>832452

dunno if it's DC or AC, better to put on a full-wave rectifier so you can crank in either direction. also need a big cap to smooth out the voltage before the regulator, so you get a clean 5V instead of a string of 5V pulses.

>>832465
Why would I need the voltage regulator if I were to put a 5V capacitor before it? Wouldn't it already be 5V? Sorry if this is a dumb question.

>>832467
A capacitor voltage rating only tells you the max voltage that can be used to charge a cap before it explodes. The voltage you get out of it is equal to the voltage you put in.

I am very stupid but I've wanted to make this variable power supply for a while now. It's the first time I ever put something together from a diagram... Before I solder it is everything ok?

>>832483
This is the underside of the prototype board I had.

>>832483
Looks like there's a short immediately after your switch. As in, the topmost copper jumper should go one row lower.
Also, while it isn't your fault, you should use smaller resistor for R1 to guarantee correct operation with light loads. Manufacturer recommends 240R. Smaller is ok, but wastes more power.

>>832492
First thing I noticed, too.

>>832483
Why do you have your components spread out over the whole board? You could do that in half as much space or less.

>>832492
>>832498
I traced it using a picture of the assembled board and found the problem I hope.

>>832492
If I can find that resistor I'll swap it out one day.
>>832512
First time doing this so it makes it easier to solder. Also I may as well just use all the space.

Does this look ok now?

>>832049
You really want your joints to be a concave cone shape. It should fill the whole pad, but not bulge out at the base. Not a huge deal for a little starter project, just a point of neatness and economy and a good habit to build for later.

>>832537

your LM317 is on backwards. the input voltage is pin 3, which is the rightmost pin when looking at it from the front, but you have the input going to 1. the ADJ pin is also swapped, so you gotta spin it around 180-deg.

I hate to pull skeletons out of the closet, but I have one final question about this circuit (if any of the anons are still around).
>>831031
>>830947
>>830936
These posts mention there being a voltage across the current sink, even when on. One post even lists it as 0.7V (apparently from the datasheet, but I am not sure to which value they are referring.) Moreover, when I am actually testing the circuit it seems as though the sinking pins do actually get connected straight to ground, with no voltage drop. What would create this voltage drop, what would it be labeled as on the datasheet, and how could I measure it?

>>832613

it's called Vce(sat), the saturation voltage of a transistor that's fully turned on. for a typical NPN, it could be 0.1V, with a rated max of maybe 0.3V.

>>832623
I think maybe you're looking at the wrong thing, but that could just be my poor understanding. The information you have got seems to be regarding BJT transistors; I was looking after the apparent 1.0V or 0.7V drop between the active pin of the A6276EA chip and ground.

The property I am confused about is referred to in these posts
>5v minus Vbe minus 6276's voltage,
(>>830947)
>the current sink pin will be at ~1V,
(>>830936)
and >>831031

well, chips are nothing but transistors and resistors inside. so the output stage is either a BJT or a FET. there's no FET equivalent of Vce(sat) but there is Rds(on) which is the on-resistance, which causes a voltage loss at a given current. it's doubtful the datasheet for the chip is gonna mention that, coz not many people care.

Behold, I finished my squirrel repelling machine and it works!

>>832627
How could I measure the Rds(on)? And are you saying that the voltage drop of 0.7V mentioned by the other anon was incorrect?

I'm a complete nub, so hopefully my non-technical explanations make some semblance of sense. I'm actually a bit embarrassed to ask, especially since the included drawing is probably totally awful:

A while back ago I made an A/B audio switch so I could connect my speakers to my PC and PS3; I did it because I needed an audio switch, but mostly to teach myself soldering and electronics.

Recently, I got a new pair of headphones, which means I had two audio inputs and two outs, so I bought a breadboard to build a slightly more complex switcher (A/B + C/D, essentially; figure A) so I could switch between PC and PS3, and headphones and speakers. This setup worked fine on the breadboard and I was going to put it together, BUT: I also have another game console, and figured I'd try to wire a switcher box so I could have three ins (PC, two consoles) and two outs (headphones, speakers).

So my question is: can I solder two wires to one terminal on one of the DPDT switches (Figure B)? Or do I have to figure out a more complex solution to switch between the three inputs?

As a follow up question: I bought RCA phono jacks to use instead of 3.5mm headphone jacks for the inputs, since the consoles use RCA connections. Would I just be able to replace two of the 3.5mm headphone jacks with 4 RCA jacks?

Sorry if none of that makes any sense.

>>832637
~1V anon here. I forgot to consider that you're switching a very small amount of current so the worst-case from the datasheet is not going to apply.

>>832645
Hey guy. Thanks for your help. Because of the indication there that the Vce is a test condition, it makes me think that this value can be controlled, rather than a value intrinsic to the chip. It's also never mentioned what Vce actually is (should I just take it to be the voltage across the device?)
In addition, I struggle to understand whether the Rext presented here will directly influence the current that can be sunk or rather will just be a limiter.

>>832637
>How could I measure the Rds(on)?
The transistor is like a resistor, so just stick a known (like 1k) resistor to a known voltage and you have a voltage divider, measure the voltage and use ohm's law.
>>832644
If I'm understanding your question right, no, you need a double pole triple throw switch, if such a thing exists.

>>832653
I'd interpret Vce as the voltage from a current sink pin to ground. Vce will go up with current, I presume.

I've never used this device so I'm not sure how Rext affects the current. It would make sense if it was a limit.

>>832655
So I can't solder the wires from two sources to one set of terminals on the switch, like in the Figure B?

I know Figure A already works, since that's what I did before, with my simple A/B switch. Would I be able to do an A/B switch, but with two things wired to one of the poles?

Obviously I would never run both consoles at the same time, so there's no risk of sending multiple signals through the wires.

> So I can't solder the wires from two sources to one set of terminals on the switch, like in the Figure B?

yes, what you're doing is, essentially, mixing the two signals. in fact, you could mix all 3 (or 4 or whatever) signals in the same way., and get rid of the switch. however, to be safe, you would add series resistors on every signal line so that the signal from one device doesnt go and hurt another device. around 1K sounds good.
or you could go for a rotary switch, 2 pole, 3 positions. (pic shows 2 pole, 6 position)

>>832653
> In addition, I struggle to understand whether the Rext presented here will directly influence the current

the big question I have is, Who cares? You seem to be obsessing over minutiae. Get it working and move on; lots more cool projects are waiting to be built.

>>832693
I've been reading around some, and with some new terminology, maybe I can be a bit more precise. What I want is to build a 3 input, 2 output passive audio switcher/matrix. I've been looking at rotary switches, but because I know so little, I can't actually wrap my mind around how a rotary switch works. Why it being in a certain position closes the circuit. I can't figure out which wire would go where.

Instead of doing two toggle switches, I think I would rather a do rotary switch (3p3t, or 4p3t with one pole being unused, if I can't find a 3p3t switch) for the inputs, connected to a dpdt toggle switch on the outputs. I would rather do a switch on the outputs, because I don't want to hear the speakers when I'm on the headphones, and I don't want to hear the headphones when the speakers are on. I could unplug one when it's not in use, but that defeats the purpose of having a switcher.

I essentially found an online instruction for what I'm looking for, this guy had a 3-output rotary switch, but I can't figure out why the wires are the way they are, or how they connect to the input jack.

>>832699
Oh, this is a link to the instructions.
https://redsecta.wordpress.com/2010/12/09/making-a-passive-headphone-or-source-switcher/

>>832644
I would go and some sort of master signal. You can add switches to mix your pc/console1/console2 in (one switch for each device with resistors like >>832693 suggested) and one switch to change output.

pic not really related, that is just my audio switcher.

>>832699
>>832644
>>832663
I'm dumb. I've been miscounting poles. My original A/B switch was a SPDT switch, the rotary would have to be DP3T.

I think I've got it figured out. Thanks for the help.

Oh, one more short question: how does one connect switches or jacks to a breadboard? Do you solder a bit of wire to the jacks first, then plug those wires into the breadboard?

>>832699

rotary switches are easy peasy. the center pins are the output leads, the outer pins are the inputs. so, in your drawing of a 3P3T ...
- the 2 output wires would come from A and B
- source 1 would connect to 1 and 4
- source 2 would connect to 2 and 5
- source 3 would connect to 3 and 6

- in the first position, the switch connects together A to 1, B to 4, C to 7
- in the second position, A to 2, B to 4, C to 8
- etc (pic is of a 2P6T coz it's closer to what you need)

>>832708

dont need no stinkin' breadboard. this is so simple, you dont have to do any testing. but, yeah, you'd solder wires.

This should be the last dumb noob question: is it a problem to solder in my bedroom? Apparently I need ventilation because of fumes, but I can't solder in the much more open living room, because my cats would never let me get shit done.

you need a an externally venting hood if you're doing this 8 hours a day, otherwise, no problem. a small fan blowing across the table helps so you dont have to blow the smoke away.

>>832713
>is it a problem to smoke tobacco in my bedroom?
Well, rosin smoke might or might not be more hazardous than tobacco smoke, but small, occasional exposure isn't going to be a problem. This isn't to say that you shouldn't try to avoid inhaling smoke.

>>832633

fuck post details and/or video

>>829986
I've been having trouble with a Sain Smart 10.1" TFT screen, although I was trying to run it with my Raspberry pi since it comes with a controller board that has hdmi input. The problem I have is that the entire display goes all white. Maybe it's just faulty.

>>832633
Pls post vid

Does anyone have the pinout of the 2005 envoy stereo connectors including the one for Onstar? I want to retain Onstar and the bongs, and I don't want to shell out $90 for the privilege of owning a couple opamps.

What is SW here? Since this is a chinese amp I don't think there's any kind of documentation. Also, this would work with headphones, right?

>>832879
Can't see where it goes, but the datasheet of the amplifier chip (PAM8403) itself is available and it has mute and shutdown inputs. It's probably one of those. Trace the signal and compare to the datasheet.

>>832890

Alright, thanks

On another note, I finally found an electronics shop near me which means I won't have to order shit from China. What are some components an electronics newbie should get? I already think I'll be getting a few NE555s and an assortment of pots, resistors, and caps, what else?

>>832900
LEDs, lots and lots of LEDs

Maybe some OP-AMPs and 'sensors' like LDRs and IR sensors, so you can play around with OP-Amps as comparators and do cool shit with that.

>>832911

LEDs are cheaper to buy from China in a 100pc assortment, and I've been delaying buying them for too long. Now's the time!

A question about potentiometers - if I have a 4700 Ohm pot, it goes from 4700 Ohms when turned all the way up down to 0 when turned all the way down, correct?

>>831027
I live in Europe and I fully agree with this guy. It's one of the worst EU directives, the Restriction of Hazardous Substances (ROHS). Lead free solder is so bad that there are a shittone of exceptions for the directive, e.g. medical equipment and automotive stuff.

I just recently got into spaceflight games, and I thought it would be really cool to have a controller like that to with a HOTAS setup.

Would it be possible to rewire a USB 10-Key to replace the keyboard keys with things like momentary toggle switches and rockers? In theory, it seems like it would be piss easy, since I don't actually have to mess with the circuit board at all, but I'm just trying to make sure.

>>832870
>>832840
I tried to post the video but it keeps saying no audio streams allowed even though it doesn't have audio. Here's the schematic though.

>>832975

ah, so you have a motion detector that causes a pump to spray some water. squirrels are persistent, so I'm guessing they'll find a way to get around it. or, they'll just ignore the water when they realize it's harmless.

if you had put a cap from base to ground, you wouldnt need such a huge value as you've used on the collector. maybe 20x smaller.

>>833048
Yea. I tried doing it your way but I was too stupid to realize I had to connect the cap to ground to make it work right so I just assumed it wasn't going to work in that position. I guess I figured out how the cap as a delay worked and then forgot about where I originally wanted it so I jammed a really big one on the wrong side to get the same result. I feel retarded but oh well, live a learn. Maybe I'll change it later.

>>833061

and while you're feeling inadequate, let me also point out that your drawing shows the relay shorting the power supply when the relay is off.

Relay question:

The datasheet says "7A 240VAC" for a resistive load. So i guess i could plug in something with up to 1680W (7Ax240VAC) written on it.

But then the datasheet says "Max. Allowable Power Force 800VAC/240W"

>240W

So could i switch something like an AC240V 1000W heater with it or it would burn out?

The datasheet: https://www.ghielectronics.com/downloads/man/20084141716341001RelayX1.pdf

The model nr.: SRD-05VDC-SL-C

>>833191
Also are these kinds of heaters pictured count as purely resistive loads or due to the wigglyness of the heater wire they are somewhat inductive?

>>833191

"800VAC/240W" is a typo, it should say VA.

as for load power being lower than the product of voltage and current ratings, this is standard for relays, transistors, chips, etc. tho, in this case, the discrepancy is quite large. so, you can use at 240V if you limit yourself to 1A, or use it at low voltage, up to a max of 7A.

>>833192

the wigglyness is insignificant. they're pure Aryan-blooded resistances.

>>833193
What kind of relay ratings should i look for if i want to switch larger heaters like 1000-2000W @240VAC.

(I am thinking about wine fermentation control and monitoring solutions)

>>833195
Resistive Masterrace

not sure if this is the place to ask, but my 180w charger for my mobile workstation recently went pop with a puff of smoke. i thought it might be a capacitor, so i rang up the local electronics repair shop and inquired about it, and he told me that capacitors dont pop when they go and the thing sounds as good as dead. problem is a replacement for this thing is pretty damn expensive and i wanted to know if anyone thinks it might be repairable at all.

seeing as its probably dead now, i could always tear it apart if anyone thinks pics will help give a clearer answer.

>>833232
Sure, post pictures.

Do you have a multimeter? It's going to be helpful when tracing down the circuit to find the broken component.

>>833235
I'll take it apart now. I don't have a multimeter, but they're cheap so I could buy one

>>833235
>>833232
shit, after pulling off the sticker i cant find any screws anywhere, and ever video i see on taking it apart seems to involve either cutting into the case or breaking the plastic at its weakest point by appliying force to it. is there any way of taking these things apart that doesnt involve destroying the case?

>>833215
Learn how to calculate power and figure it out

>>833242

They can't, they're welded ultrasonically (it's a thing) and without cutting into it you're going to have a hard time getting in.

Picked up a Roomba with charging dock, two walls, complete Roomba, and a spare set of brushes for $15 from the thrifty store yesterday. I crakced open the battery and found that 5 of the 16 cells are kaput. Right now I'm trying to decide if I want to attempt to replace the cells with Panasonic lithiums (with proper protection of course) or if I want to just hop down to batteries plus and pick up five new cells.

>>833257
Fuck ultrasonic welding. Shit needs to stop.

>>833257
Damn it, fucking wankers

Is it possible to modify power adapter to povide little bit more voltage and amps

Its a HP printer adapter 32VDC@625mA(actually 31V measured) which i would like to use to power 30W led chip that works at 32-36VDC@600-900mA

Old one is fried(?) i guess though i thought about changing the caps to see if it will work maybe

>pic related is original one

>>829762
Make a Ring Modulator!

>>833215
>What kind of relay ratings should i look for if i want to switch larger heaters like 1000-2000W @240VAC.
look on ebay for "mechanical relay 480v" and you will get results showing industrial-sized relays.
most of the 480v ones can handle 25 or 40 amps. Many cost under $20 each.

>>833266
>Is it possible to modify power adapter to povide little bit more voltage and amps

nope, but you can wire 2 similar units in parallel, using diodes, to increase current, or in series to increase voltage, or both, if you have no shame.

>>833266
>Is it possible to modify power adapter to povide little bit more voltage and amps

nope, but you can wire 2 similar units in parallel, using diodes, to increase current, or in series to increase voltage, or both, if you have no shame. you just have to be sure the power supplies use 2-prong 120V line cords, with no ground wire.

>>832483
Consider adding a bleeder resistor if you built your own rectifying circuit. Also, you should test it on a breadboard before you solder anything. This hold true with almost all projects. Also, be sure to use the equation provided by your regulator datasheet and find the resistor values you need for the output voltage range you want. Otherwise you may end up with a super sensitive circuit. I recognize that particular schematic and it looks like something from instructibles. If it's the schematic I think it is, then they have the pin labeling wrong. Your adjust is 2 not 3. Double check the datasheet though.

>>833337
Just looked up the datasheet. 1 is adjust, 2 is out, and 3 is in.

Slowly getting there

What is this? I mean it's obviously a transformer but anything special about it? also why are the wires curved like that? is it to show that its AC? I figured the other parts that say AC covered that. I have 2 more diagrams with questions if anyone would be so kind.


>>>/g/48750540

I started thread in G if you want to just look at it before i post everything in here.

>>833442
Curved wires are fuses. Americans like that symbol.
Nothing special in that transformer, or at least your schematic does not indicate that it's special.
https://en.wikipedia.org/wiki/Fuse_(electrical)

>>833444
Fuses! okay, makes sense, thanks!

Would you happen to know about this one? The thin that throws me off is the unmarked circle(which im assuming is a motor) and the circle with the 'x' like pattern on the outside.

>>833446
It's ladder logic symbol for a relay. Crossed circle is a lamp.
https://en.wikipedia.org/wiki/Relay_logic

>>833067
wait, i don't get it, how is it supposed to be drawn?

>>833067
wait, why? how is it supposed to be drawn?

I ordered some of these
https://www.google.ca/url?q=http://www.mouser.com/Search/m_Search.aspx%3FKeyword%3D689-HV5622PG-G&sa=U&ei=cuORVfDhEMyXygSLk5HAAg&ved=0CAsQFjAA&sig2=r2zy0yxXTVCX9PhgFZs7SA&usg=AFQjCNGNptnovUhqa7QE
iUsPOsRxQtIbzg
And the packaging mentions a date before they must be used. How do I "use" them? Does it just mean that they must be soldered before the date? They're also sensitive to moisture so does this mean that, once soldered, I need to be weary of the environmemt I use the final project in?

>>833515
Can you link to a datasheet. Your link turns up a list of different parts.

>>833523
Datasheet on mouser just links me to this generic page that doesn't say much. But the part number is 689-HV5622PG-G

>>832975
>>833509

>>833537
wait...if i don't have it like that, how is the circuit supposed to be completed? fix it for me so i can understand what you're saying because i'm not getting it...i thought that's how it is wired up and it works fine.

>>833537
wait...if i don't have it like that, how is the circuit supposed to be completed while the relay is off? Because i'm trying to show it off in the schematic. fix it for me so i can see what you're talking about.

Anything wrong with this PCB?

>>833546
Here's the schematic

>>833537
OH WAIT, it should be like this right?

>>832975
>>832975
post it on the alt chan and literally just move there.
(funny how I couldn't say it's name )

problem is your video has an audio channel but with the volume set to zero.

>>833215
>>833303
At that rating, I found it easier to go relay to contactor, I arduino webserver'd the pool's lighting with this, and I already had contactors laying around the shop, and in one instance, is used for controlling the compressor on AC units,

>>833262
You can buy a pre-welded set of nicads. But it's unusual to have completely dead cells.

>>833546
>Anything wrong with this PCB?

the biggest thing wrong with it is that it's too small to be worthwhile. in a race, i could finish wiring and testing that on perfboard before you're even ready to drill the holes.

>>833577

suggesting contactors is only cool if you have some laying around, coz those are like 10x - 20x as expensive as a relay.

>>833602
>But it's unusual to have completely dead cells.

no it isnt, every single pack of Nicads will have one or two cells short out before the others. oddly enough, even tho they're in series, the sequence is not random. it happens most often at the + end of the pack. no one knows why.

just a quick stupid question,

Is using a normally on button with an mcu a huge waste of electric?
Iisnt the switch basically allowing a constant drain on the batteries UNTILL the button is pushed?

>>833618
What are the downsides of it being too small?

>>833637
depends on what it's connected to?

most MCU inputs don't draw very much current at all— they're just MOSFET gates (and some protection diodes and crap)— so the current draw is just whatever pulldown you have

>>833640
right, so if you are trying to jew your batteries using those things is just stupid so why do companies default to those instead of normally off buttons and just reading when the current is flowing?

>>833192
Some people like to believe that their electronics are pure blood, but all electronics have some resistance, capacitance and inductance. The spiral wire will have more inductance than a straight wire. The inductance is very very small and can be assumed purely resistive unless you are using it for high frequency electronics.

>833639
>What are the downsides of it being too small?

I already said: below a certain level of complexity, it's less work (faster) to assemble the circuit using another method such as veroboard or perfboard, or even point-to-point.

>>833639
>What are the downsides of it being too small?

I already said: below a certain level of complexity, it's less work (faster) to assemble the circuit using another method such as veroboard or perfboard, or even point-to-point.

>>833643
If you have just few switches, their current can be made rather insignificant in comparison to everything else. In desperation you can also power them from controller IO pin.

u mirin, /ohm/? c:
I am also open to suggestions to what to do with them

>>833660
Can you identify them? There could be some very rare part numbers in there. I recently had to fix a piece of equipment where the power transistors were obsolete and cost 50 bucks a piece. I found an equivalent replacement of course, but it would have been much easier to just get an original. If they have the part numbers you should test them, shine them up, straighten their legs, and put them up on ebay for ten bucks a piece with their part numbers.

>>833661
Sorted out. Some of them are just simply unknown since corrosion ate away the numbers
Known and identified : AD161, AD 162, AD149 , Tungsram : OC26 ,ASZ1015, ASZ1016, ASZ1017, ASZ1018
Mostly germanium
Would rather use them than sell

>>833663
1. genuine-authentic sixties transistor amplifier with horrible sound quality. I have Philips' application notes/schematics for "good" amps, if you're interested.
2. Open them. With some luck you'll get small amounts (1-2mm^3) of indium.

>>833667
>Open them. With some luck you'll get small amounts (1-2mm^3) of indium.
For what purpose?
>I have Philips' application notes/schematics for "good" amps, if you're interested.
Throw them at me or point me in the right direction, I'm not an audiophile anyway, so what

>>833671
>For what purpose?
arse insert.
sealing stuff for vacuum
glass metallization

Pic: Philips car radio amp.
Sorry about potato pic, but at least it should be readable. This is from book Semiconductors and integrated circuits, part 2, october 1968, by Philips/Mullard.

>>833684

Am I correct that with a basic 555 astable circuit, I can control both the T1 *and* T2 time by changing the value of R2? Or will it only change one of the values?

>>833801
Yes. No.

>>833801
You need a 'slightly' different design to control both ON and OFF time.

>>833818
>>833801
You want this.

http://www.ic-elect.si/pub/files/product_files/650001110100.pdf

I live in an apartment. What should I use to ensure good airflow so that I won't pass out from fumes?

>>833818
No it's fine, I *want* T1 & T2 to be the same, hence my question.

>>833900
That sure was a roundabout way to ask it.
But yeah, the basic 555 astable is not capable of producing symmetrical square wave. You need to use different circuit.

Let's say I have a 10:1 transformer, 120V 60Hz AC on the primary. If I use 250kcmil copper cable for my primary but 1000kcmil copper for my secondary what affect will this have on the transformer if any, voltage/current-wise?

This isn't for any particular project, just curious.

>>834151
Wire cross section has an effect on the resistive losses and that way to the load regulation. The thinner wire you use, the more the voltage sags when you load the transformer.
It is generally a good idea to use roughly the same amount of copper (measured in grams or cm^3) for both sides, because the smaller winding dominates the losses.

I want to make a small solar charger with a 3,7 Li-Ion cell as main storage used when it's cloudy. While I could do it in a convoluted way, I can use a power bank circuit which takes care of both interface, battery protection and charging. However, my 0.8W (Thought I think I'll get another one, as considering inefficiencies i'll have about 0.5W of charging power) solar panel has a peak voltage of 8V in direct sunlight. Do I just use a L7805 to regulate that, or what?

If I were to do it in a convuluted way, wouldn't a zener diode with a zener voltage of 3.5v be enough for a cut-off battery protection?

If you took a bridge rectifier and hooked it up to a wall socket, how much DC voltage would be output?

Since it's 120V AC what would the DC turn in to?

Is this even possible?

>>834179
Yes it is possible.
https://en.wikipedia.org/wiki/Rectifier#/media/File:Gratz.rectifier.en.svg

You would get a maximum of 120*(sqrt(2)) VDC, and a minimum of 0 VDC.

Be very careful though around AC line voltages.

t. amateur electronicsman

>>834175
>a power bank circuit

presumably any kind of circuit with that name would be sophisticated enough to accept varying input voltages. if it were a ''USB power bank circuit'' then it would likely only work at 5V. anyway, series zeners are bitches, coz they always steal their rated voltage, whether it's sunny or cloudy. however a zener in a shunt regulator would not steal voltage, but just get hot.

>>834182

It's an USB 1-cell circuit, so I guess I'll have to use the L7805. But if I ever want to make a simpler one, I'll remember this regulator. Thanks!

>>834181
So you will get the voltage equivalent to the RMS value? That's what I was thinking it'd be.

>>834185

you're better off looking for a LDO regulator that will only steal, say, 0.2V, as opposed to the 7805's 2 volts.
https://www.jameco.com/1/3/ldo-5v-regulator

>>834189
Technically speaking full wave rectification does not change the RMS value (if not counting losses).
However, how much your pulsing current is actually worth depends on your load. A resistive load would see the RMS value, while an average-reacting load like motor or solenoid would see around 90% of the RMS value. And if you add a big enough capacitor in parallel with the rectifier, the measured voltage would be around 1.4 times the RMS value.

>>829678
>Bought old Roomba for $10
>Battery is potato
>Get battery apart
>Five cells are either completely flat or shorted out
>Could replace cells
>BUUUUUT
I could pick up 10 Panasonic cells from eBay, as well as a balancing/control board. Would it be worth it however? What about housefire chance, seeing as this board is Chinese as fuck? It looks solid, and boasts a control chip from Seiko.

>>834262
$10 for an old roomba
Where

>>834264
Thrift store. Came with charging dock (like the self-landing kind), two walls, charger, and a spare set of brushes. They sold it at that because the battery was a 'tato, and they didn't know if it worked or not.

How am I supposed to use flux? My solder has it anyway, I have a paste one and a resin one.

>>834427
Flux cleans the surface of the metal as it burns off so the solder can bond. If you're already using flux core there's not a lot of times you'll need to use a separate bottle of it.

Say you want to spread a very thin layer of solder over a big flat surface. This requires a large amount of flux to cover the entire surface, but not a lot of solder because you want a very thin layer. The copper to flux ratio in your solder won't be right this case. Use a small brush to paint the surface with a thin layer of flux.

>>834427
https://www.youtube.com/watch?v=J5Sb21qbpEQ

watch all 3 videos, they're pretty helpful.

I bought this transformer from radioshack today because I'm trying to build a power supply. It said 12v with a center tap on the box, but the transformer itself says 6.3v - 0 - 6.3v; each of the windings is only 6v, not 12v. I've been looking around at voltage doubling circuits, but they all seem to drop me down to the +- 10-11 volt range when all is done, which is too low. Tripling and quadrupling circuits have way too much ripple even when using all of the largest capacitors I have on hand. I wouldn't even be able to regulate it down to +-12v because of how much the voltage dips on the negative swing. Is there an elegant solution to this problem besides simply getting the "right" transformer?

>>834479
It's a 12v difference between both end taps, no?

yes. It's 12v end-to-end, 6v from each end to center.

I don't even know what the fuck that would be useful for. What kind of circuit requires a +-6v supply?

>>834479
I had an idea:

If I got two identical 120v - 12v transformers, then wired the mains side in parallel and the other side in series, would this effectively make a 24v center-tapped transformer?

>>834479
Yeah, not practical to get +-12 out of it.
>>834495
Yes, this would work.

>>834479

i've used this voltage doubling circuit in the past many times successfully. with it, you should be able to get around +-15V with a reasonable output current. you wanna use some fairly large caps, at least 2uF per mA of output current.

>>834544
the voltage I will get will depend entirely on the transformer I'm using. The one I have is 12v, so double would only at best put me at 24v, not 30 (or +-15)V

I'm thinking about just using a separate supply for part of the circuit so that the current demands aren't so high on the split power supply. It's a audio compressor circuit using a 12v light bulb and a CdS photoresistor. The op amps and shit need a split supply, but the bulb, which is going to be drawing most of the current, is just 12v. I've got 3300uF caps, which are way more than enough for a few op amps and a couple of leds. I'll run the bulb and the mute relay off of a separate 1A 12v power brick I found in my pile of shit.

>>The one I have is 12v, so double would only at best put me at 24v, not 30 (or +-15)V

this misunderstanding again! third time in a week. the peak voltage of a 12Vac transformer is 17V. when you rectify and filter the AC, the resulting DC is close to this peak voltage. subtract a little for the diode loss, and a little for loading, and a little for ripple, and you should get around +-15Vdc. unless you try to pull a heavier current than the transformer is designed for.

as for using 12V light bulbs, it's important to consider the wattage. most of those you find are powerful bulbs used in cars and patio lighting, but there exist tiny ones which draw very little current, around 50mA, such as used in old telephone equipment (before LEDs), etc.

here is an living proof: 12Vac 300mA transformer using voltage doubler putting out 29Vdc at 250mA load.

>>834563
Lick it.

>>833446
on left is a NO pushbutton
in middle is guessing motor and contacts
on right in the 0 VDC line is a lamp, probably a pilot lamp to indicate running

source: education

Can someone post the challenges?

>>834486
Valves (tubes) use 6.3 V AC for the heater.

>>833801
> Am I correct that with a basic 555 astable circuit, I can control both the T1 *and* T2 time by changing the value of R2?
Yes.

Charge time is determined by C*(R1+R2), discharge time by C*R2.

If you want a symmetric square wave, make R1=R2 and put a diode across R2 (so that R2 is effectively 0 when charging).

In average, how expensive is to get some tools and parts and start doing things?

>>835190
That depends a lot on what you mean by "doing things" and how ghetto you're willing to go.
The most important tool is your multimeter, and you can get one of those for $10 at walmart or menards or wherever. Don't bother with an expensive digital one, the cheap analog ones are much more useful on their own because they can show slowly changing signals and you don't have to worry so much about breaking it.

If you're doing original and complex designs you'll probably want a breadboard. A small one for simple projects would be around $10, a large one maybe $50.

If you want to make things permanent you'll need a soldering iron. You can get a cheap one for $30 with enough solder to last you a little while.

A wirestripper can be very handy, but a knife will work too.

For a power source you can use batteries or the wall adapters that come with electronics like phones and laptops for most projects.

If you have access to lots of old junk ("old" being the key here -- new junk is mostly made with tiny SMD components that are hard to work with) you can salvage pretty much anything you need. You have to be pretty tight to go that route though, after spending 20 minutes finding and removing a 10¢ part you'll probably decide to spend $10 on a resistor kit. Depending on what you're doing you can get kits for ceramic and electrolytic capacitors, transistors and diodes for around the same price. Wire can be salvaged, but the solid core wire used in breadboards isn't that common.

So the range there would be around $10 (multimeter only) to $160 (meter, big breadboard, soldering iron, wire strippers and wire, and kits of common components)
Obviously you can go over that (oscilloscope, nicer soldering iron, bench supply, specialty components etc.) but there is a lot you can do with a basic setup.
And of course if you just want to get hipster chicks wet all you need is an Arduino and an LED.

>>835221

fuck you, dude, dont reply to such obvious trolling.

Is there a differential amplifier setup that calculates the difference of the two inputs and invert it. For exemple, if the difference is -2V the output of the op amp is 2V.

>>835445
You mean a subtraction op amp cascaded with an inverting op amp?

I've been tryijg to desolder some ICs for 20 minutes and I couldn't take out a single one. What am I doing wrong? I've been putting the wick over the leads then used a small pointed tip.

>>835461
Yes, but without the cascating part. I toight there was a way to use the same op amp. In my actual setup, I am cascating them but I'm getting some voltages divergences. The inverting amplifier is with a gain of 1 and I still get some voltage divergence. The problem is that this divergence is not linear.

>>835471
Swap the inputs

>>835471
Also, make sure you properly powered the op amp.

>>835471
But did you fix it

>>835471
If R1 = Rf and R2 = Rg, the output voltage should be V2-V1.

But note that R1 and R2 must include the output impedances of the preceding stages. If those are variable or unknown, R1 and R2 must be high enough for them not to matter. At the same time, R1 and R2 need to be low enough for the input current not to matter.

Total and complete beginner here.
I'm attempting to wire up my bicycle to have blinkers and an actual tail light instead of a reflector.
Would the circuit only need to contain LEDs, switch and battery? Or is there something else I'm forgetting, like to regulate the power or something?

I thought this would be a good thread to ask for some advice.

Can anyone tell me if Trade School is a good choice? Im 19 and torn between going to college or trade school. I want to become an electrician though, I always liked construction.

>>835766
Sure if you think you'll enjoy it, however electrician =/= electronics

>>835769
I understand that.

This is just the only thread that could offer some good advice. /diy/ is the most useful board for asking my question too.

>>831376
Bump. I want this too. A while back an anon said that he would scan the 3rd edition once he got it. so we must wait...

>>835701
LEDs normally need a resistor for current-limiting. Constant-current LEDs exist, but are more expensive than plain LEDs.

>>836221
>>836221
>>836221
>>836221
new thread