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/diy/ - Do It Yourself

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30823 No.30823 [Reply] [Original]

Greetings Makers. I am an avid maker and student of electrical engineering. I just thought I would drop by to try to answer any EE questions that may be plaguing your projects or minds. Any other guru's out there feel free to jump in as well. Only limit is that I will not design your project for you, nor will I fully address questions that require a 3 hour lecture to understand. Will be on for at least an hour.

"No excuses, just make something."

>> No.30841

In the mean time, I will discuss a few things of interest. One of which is the new Kinetis Cortex microcontrollers from freescale semiconductor. Some of these models come with onboard usb and lcd driver support, and high clock speeds into the 100mhz range. I don't know if anyone else has seen or heard of these, but they look like they will be exciting to work with.

>> No.30855

All of the cortex MC's are 32-bit, and many of them have onboard 16-bit ADC's. The only thing that bugs me about them, is that they are not being very upfront about how we are going to have to program these. Chances are, you will have to have a specific programmer for these, but they provide a lot of horsepower and could be used in a lot of projects where an arduino or pic is simply not powerful enough.

>> No.30856

design me a diy dragon dildo

>> No.30860

How many volts does it take to power an off-shore oil rig?

>> No.30862

>>30855
Speaking of which, I was just looking into:
http://www.st.com/internet/evalboard/product/252419.jsp

>> No.30864

What do electrical engineers like you actually do? i don't mean it in a bad way but what do you do on a day to day basis and what do you work on/build/design?
And how much money do you make?

>> No.30869

>>30862
very nice. Thank you for pointing me in that direction. I have been looking into a dev board for Cortex ARM. They are really interesting little chips.

>> No.30873

>>30864
program drivers for embedded devices
80k a year

>> No.30874

what's the most advanced math you use on a regular basis? As far as generic math classes (algebra, calc, etc.)

>> No.30876

>>30869
They were (are?) giving them out for free. I hope my order goes through.

>> No.30881

>>30864
I am currently a student, and although very close to graduation, I have not yet done any actual field work yet. However, most of the people I know who work on design teams pretty much say that they stay very busy moving from one project to the next. Unfortunately a lot of the projects "dissipate" as they call it. So really, you get to do a lot of work on things that will never make it out of the development environment. Pretty much the same story for hardware and software teams.

>> No.30889
File: 104 KB, 317x247, pickit3tools.png [View same] [iqdb] [saucenao] [google]
30889

For anyone interested in starting with microcontrollers, you may want to pick up one of these. The PicKit 3 from Microchip. It is an in circuit Pic programmer, and they even have a model that comes with a Pic dev board all for under 65 USD. Even comes with the programming software, although a very lite version.

>> No.30907

More interesting devices for projects:
http://www.mouser.com/ProductDetail/Silicon-Labs/Si4844-A10-GU/?qs=sGAEpiMZZMswyCOIqqEme9p7c3sQY%252
bXfCoP5AzOh0rc%3d

This little beauty is an AM/SW/FM radio on a chip. They basically contain the entire radio on the chip. They cover "64 MHz to 109 MHz, 504 KHz to 1750 KHz, 2.3 MHZ to 28.5 MHZ" and only require a few resistors and a potentiometer for tuning and band selection. A MCU can be used for frequency display and for digital control. Currently building a shortwave radio for personal use with one of these.

>> No.30922

If you are board would you mind telling me what EE or CS classes you took for your major and what you did in them, I just want to compare it to what I have been doing. Also if you don't mind what University are you attending.

>> No.30932

>>30922
I am attending the University of Arkansas Little Rock, and have had the usual classes such as circuits 1 and 2, digital system design, microprocessors, data acquisition, robotics and PLC's, Digital signal processing, and a lot of other classes. Most of the others build on the ones listed.

>> No.30934

>>30823
I'm not OP, but I work in a consulting office. I work with a team of people on heavy industrial projects. I specialize in instrumentation and control systems.

>> No.30936

I'm looking at making this project, I have the parts coming in the mail already, but I'm wondering how many amps this thing is going to pull. I'm guessing less than one but I don't know for sure.
Also, if the output voltage swing to the current limiting resistor, transformer, and reverb tank is twice the supply of 12V, how high of a power rating should I get on the transformer? Someone recommended a part from mouser but its only got like 480 mA rating, which doesn't seem like enough
link: http://www.solorb.com/elect/musiccirc/reverb2/

>> No.30938

Is ground-theory actually important?

>> No.30943

Almost any university will offer the same things under slightly different names. Best advice I can give you though is to step outside what they offer as often as possible. Learn as much as you can about what the teacher didn't say. A lot can be learned from data sheets as well. Since you will be working with components, learn about them. Discover interesting ones like that one I posted about the AM/SW/FM chip.

>> No.30945
File: 77 KB, 1200x1310, resistanceisfutile.jpg [View same] [iqdb] [saucenao] [google]
30945

I've got one. A resistor burnt out in my Monster iplay plus cable. The issue is that I'm not sure what its resistance is because it's burnt. It looks like it's red orange silver gold, or maybe orange yellow silver gold.

The issue is that if you'll notice the second band is made up of two colors, it looks to have changed when it burned out...

Also, the pics were taken by taping a 10x loupe to my cellphone cam. One of the more helpful things I've come up with to deal with not having a real camera...

>> No.30948

I want to run a 5V LED on a AC 12v system

So I take the LED, put another diode going the other way, solder, then on one end I put a resistor, right?

(LED)______{Resistor}_____-Neg-
...|.........|
...|____[Diode]
...|
+Pos+

>> No.30953 [DELETED] 

>>30948
Or do I put the resistor inline with the LED only, and which side do I put it on? It is a lot easier to source 12v diodes than LEDs

>> No.30955

>>30936
I'm sorry, 460 mW rating on the transformer
does that even matter for AC though? I'm pretty new to all this

>> No.30959

>>30948
>>30948
Or do I put the resistor inline with the LED only, and which side do I put it on? It is a lot easier to source 12v diodes than LEDs

Also, I went full retard. Obviously because it is AC, there is no positive/negative

>> No.30960

>>30948
isn't the diode redundant?

>> No.30962

>>30945
If its just a surface burn you _should_ be able to check the resistance with a multimeter. If not, it just looks like red - yellow - silver - gold, to me.

>> No.30966

>>30960
I'm under the impression that trying to power a LED backwards kills it quicker and gives it a higher chance of dying. Obviously the whole point of a LED is to never have to deal with that crap.

>> No.30971

>>30966
watch the max reverse voltage listed on the datasheet

>> No.30973

>>30936
It looks like the project calls for a standard audio isolation transformer. I would say something like http://www.mouser.com/ProductDetail/ICE-Components/CT04-070/?qs=sGAEpiMZZMv0IfuNuy2LUcVsRIVRe3HbC%2f
W74a%252bpkPk%3d would probably work

>> No.30976

how can i generate static charge ?

>> No.30977

>>30966
it's not the reverse bias that reduces its lifetime (you wouldn't even notice it anyway if its just for a prototype), its the fact thats switching on and off.

>> No.30979

>>30962
You know, I didn't even think of testing it, I assumed it was just dead. So I just checked it. I was right.

Thanks for the reply.

>> No.30982

>>30977
So I need a capacitor to smooth it out?

>> No.30984

>>30973
holy shit, 20A max rating? and good frequency response too.
the ratio says 1:70, so that means if the transducer on the output is 8 ohms impedance it would reflect a 560 ohm input impedance right? Or is the math more complicated than that...

>> No.30985

>>30977
Also, it isn't a prototype. I'm replacing the indicator lights on a vehicle. Runs off of alternator power, the bulbs are dead and I thought I should replace them with LEDs that should outlast everything else.

>> No.30998

>>30985
I would just put the R in series with the LEDs. They aren't going to be blinking on and off all day are they?. Check also if the datasheet says anything about using them with AC. Many times the datasheet comes with example circuits and recommendations under diferent conditions.

>> No.31005

>>30998
Wouldn't a diode bridge solve your problem?

>> No.31006

>>30984
70:1 isnt exact, but it is pretty close for that project.
The amplifier output is around 500 Ohm and would yield 7 ohm into the reverb. So it should work.

>> No.31009

>>30998
I'm just going to use generic Chinese LEDs. Yes it is going to be constantly blinking. It is running on an AC power wave. That means several cycles a second.

>> No.31011

>>31009
oh well just do this then.
>>31005

>> No.31015

>>31005
For a few LED's, a single diode and a capacitor to smooth it out should be fine. If you are talking about powering a large grid, you are going to want a proper power supply. Also, you will probably not want to dump 12v onto an led, depending on the type. An option would be to power them by a common anode supply using a zener diode to step the voltage down, and individual current limiting resistors for each led.

>> No.31020

>>31005
So do I actually need 4 diodes for just 1 LED? I have space issues as well, and my soldering is not that great.

>> No.31024

>>31015
Can't do because these are indicator lights connected to different things, meaning I need to drop the voltage for each LED individually, unless I want to make some sort of transistor thing. Resistors are easier to get, and I figure these should draw less wattage than filament bulbs even with resistors.

>> No.31025

>>31020
not him, but I was confused. Thought you said LEDs not just one. In that case a capacitor would be enough. But remember checking the datasheet before anything.

>> No.31026

>>31020
For 1 led. I would use a single diode and single capacitor to smooth it out unless you like a 60Hz blinking light.

>> No.31027

>>31006
Thanks for the help, I was thinking that other part was a bit low of a wattage rating for this application. I couldn't find other transformers because I was looking by impedance and not ratio.

>> No.31029

Hello OP,
After working with ATmega/tiny a (small) bit and some MSP430 experience, I am looking to use the XMEGA for a project I'm working on.

How should I proceed? I've been reading some appnotes... In terms of the toolchain, I've thinking of buying an MkII or an AVR Dragon. Is OCD worth the extra $15?

Also, how should I get started programming? I'm good with C, but haven't done much in relation to micros. Planning on using AVRlibc, and not sure where to get started. It seems every library has a different format, which makes finding code examples difficult.

>> No.31035

I want to make an R/c timer circuit that drives a couple of LEDs. Nothing specific, just maybe point me in the right direction as far as some further reading, simple schematic, or parts list?

Thanks!

>> No.31036

If I needed a +/- 15V power supply, and I've only got +32V DC, can it be done? Or do I have to tap the rectifier directly? (which I can't do from my wall-wart-esque power supply)

>> No.31037

>>31035
555 chip maybe?

>> No.31046

>>31025
>>31024
There are a number of LEDs, but they are all connected to different things. I think there's 3 different alternator feeds, and all of them power things that need full voltage. Basically, each one needs it's own circuit, so obviously, when I have 10 different indicator lights, keeping part counts down is good. I think it runs from 1000-7000 rpm and I'm not sure what the magnet/coil setup on the alternator is. Power draw isn't a major issue because they're replacing fillament bulbs.

>> No.31048

>>31029
If you are familiar with loading the programs onto the chips, the next step would be to find some program for the specific chip that will allow programming in higher level languages such as C. I am more familiar with PIC microcontrollers and some ARM MCU's, but I expect that they offer some sort of free program. Obviously the datasheet is the best option for seeing what the pinout is.

>> No.31055

>>31026
I don't know how it would affect the component, but almost all house lights flicker at 60Hz, you won't notice a thing.

>> No.31057

>>31036
What you want to build is a virtual ground circuit. It simulates center tapping a battery. The one using an op amp is the easiest to build. Make sure you use high precision resistors to make sure the division is even.

http://tangentsoft.net/elec/vgrounds.html

>> No.31066

>>31055
I don't think it would reduce the life. PWM is often used to dim LED's after all.

>> No.31069

Man...some of you guys come up with some really good questions. This is good practice for job interviews. I especially like the +/- power supply question.

>> No.31074

Hi OP I have a very nooby question for you, can you explain Ohm's law to me please?

>> No.31079

>>31069
Well thanks man, necessity is the mother of invention. I've been thinking about it because I'm eventually gonna need a +/- supply and I'm too stingy to pay 80+ dollars for a professional one.

>> No.31080

>>31069
I don't think its possible

>> No.31083

>>31074
Indian sees eagle over rabbit
rabbit sees eagle over indian
eagle sees rabbit next to indian
(i think thats how it goes)

>> No.31087
File: 53 KB, 576x720, 1316843322652.jpg [View same] [iqdb] [saucenao] [google]
31087

>>31074
I would help explain, but I need to go sleep. Check out:
http://openbookproject.net/electricCircuits/DC/DC_2.html
http://www.allaboutcircuits.com/vol_1/chpt_2/index.html

and the pic should help.

G'night everyone

>> No.31088

>>31074
Ohms law is as folows:
V=IR (volts = amps * ohms)
P=VA (Power (watts) = Volts * Amps)

The trick is that if you know two you can figure out any of the others. For example, a 10V battery fed into a 1K Ohm resistor will have a current of I=V/R and equal 10mA. The circuit would draw a power of P=V*A and equal 100mW.

There are other derivations of ohms law such as
P=I^2R
P=(V^2)/R
etc. Good algebra skills helps.

>> No.31093

>>31088
Please note that this applies to all circuits, but can get complicated real quick when capacitors and inductors are used in AC circuits.

>> No.31096

>>31036
This is probably the dumbest way ever, but you could wire the DC supply into a motor, then configure that into a generator with magnets and wire loops, and then use a transformer to tweak the voltage.

>> No.31100

>>31093
is that because it's not "tuned" or is there another reason?
how come the datasheets never state reactance?

>> No.31101

>>31088
>>31087
thank you guys, much help. Been making small simple stuff lately and wanna start getting into more serious projects

>> No.31106

>>31096
not dumb in theory, it's just pretty impractical

>> No.31111

Pop quiz:
V=12V < 0
Frequency = 1Khz

What is the impedance of a 1kohm resistor in series with a 10mH inductor.? Bonus points for giving the answer in rectangular and polar form.

>> No.31116

>>31100
Reactance changes with frequency. So it is not a definite value.

>> No.31124

>>31100
In AC circuits, inductors and capacitors offset the current from the voltage, since they have a complex impedance. Ohm's Law will apply for the RMS (root-mean-square) values, but not necessarily for the values at some specific time.

Someone correct me if I'm wrong, my experience with AC is rather limited.

>> No.31126

The reactance of an inductor and capacitor is as follows:

XC = 1/(2(pi)F*C)
XL = 2(pi)F*L
frequency in hertz, capacitance in farads, and inductance in henries.

>> No.31129

>>31124
You are correct sir. a capacitor has an impedance angle of -90 and an inductor has an impedance angle of 90. What this means is voltage is 90 ahead of current in an inductor and 90 behind current in a capacitor.

>> No.31132

>>31111
118 ohm polar, 100 rectangular?
really all I did was google impedance calculator and plug in the varaibles. It didn't ask me for voltage though so I might have done it wrong

>> No.31136

>>31132
oops, thought you saiid 100 ohm resistor
new values came out to 1001.97 and 1000

>> No.31141

So the solution to the quiz is as follows
XL = 2(pi)(1000)(10X10^-3)
XL = 62.8 ohms
XR = 1000 ohms
Rectangular impedance = 1000 + J62.8
Polar = 1001 < 3.6

>> No.31146

>>31141
so I basically got it right without even understanding it, just by googling and plugging in numbers?
way to go google

>> No.31149

>>31146
The most powerful tools known to man. Google and wolfram alpha.

>> No.31158

I know nothing about electrical engineering. Where should I start?

>> No.31162

>>31158
http://electronicstheory.com/COURSES/ELECTRONICS/e101-1.htm
it kinda sucks toward the end though, pages are missing n shit

>> No.31164

This has been a fun and productive evening. Signing off.

>> No.31168

>>30823
i plan to build up a zeppelin flying thing. i need an intregated circuit that will allow me to wirelessly control it's rotation and compatible with hand made sensors and maybe a live information transmission, like images, sounds, values, etc. also it has to be very light, most PICs i know are too heavy.

>> No.31174

>>31168
just buy one of those air swimmers fish and mod it
http://www.youtube.com/watch?v=vIJINiK9azc
(helium not included)

>> No.31181
File: 315 KB, 990x879, Buchla200e.jpg [View same] [iqdb] [saucenao] [google]
31181

How difficult would it be to create a rather large modular synth?

>> No.31186

>>31181
pretty hard, and if you do it's not going to look like that pic (look at all those fucking ins and outs. amazing)

>> No.31187

>>31174
HOLY SHIT THIS IS AWESOME
but i still want to build something like that myself. i kinda have a promise to fulfill. well... i was thinking about using heli blades but now this swimming thing looks more practical and easier to build.

>> No.31193

>>31187
yeah, those are supposed to be the big christmas toy this year
I'm considering buying some or some helium to resell at inflated prices, but I don't know if they'll be THAT big.

>> No.31199

>>31174
>>31187
dealextreme sells those for $30 with free shipping (helium not included), much less than the $42 + shipping other stores are looking for.

I used to have an rc blimp (got for dirt cheap at a local electronics store that went bankrupt, dunno why they had rc blimps) and to be honest those things are highly overrated. Moving forward is easy but as soon as you want to go backwards its like driving on ice. Also due to the slowly escaping air pressure, you have to adjust weights on them to keep them stable (not moving up or down all the time). It cost me about $6-7 to fill it up at a dollar store. Also they lose air pressure after about a month to the point where it is unable to fly.

http://www.dealextreme.com/p/cool-rechargeable-2-ch-remote-control-flying-clown-fish-air-swimmer-ora
nge-103928

http://www.dealextreme.com/p/cool-rechargeable-2-ch-remote-control-flying-shark-air-swimmer-blue-103
643

>> No.31208

>>31199
yeah, for some reason one time my father told me nothing really holds helium 100%, not even glass

>> No.31230

>>31199
thats pretty cool and stuff but i still want to build something like that myself. i don't think it would be worthy it if i bought and entire shark thing just for it's components, but thanks for the tip. that's giving me a few ideas.

since the original idea was to build a heli pads + helium robot, i think i'll be happier in the "flying backwards" thing and rotation speed.

>> No.31249
File: 17 KB, 300x354, 070402102819.jpg [View same] [iqdb] [saucenao] [google]
31249

>>31230
if you took it to the extreme, you could build some kind of vertibird thing with a helium balloon and some helicopter rotors that could be tilted to change direction.
maybe even sort of like a square pattern in a way that reminds me of a box jellyfish

>> No.31262

>>31249
http://www.youtube.com/watch?v=F_citFkSNtk

something like that already exists

well, my prime idea was a sphere filled with helium surrounded by 3 horizontal toy helipads, disposed in a "peace symbol" form. the batteries and circuits would be right under the ball the give it stability.

>> No.31270

>>31262
Speaking of such things:
http://www.youtube.com/watch?v=L4OUqShxhh0

sphereocopter

>> No.31288

>>31270
HAHA shit, that's fucking cool. it seems faster and 10x more stable than my protect. but it seems really hard to build with bare hands.

>> No.31331

http://www.youtube.com/watch?v=pgqmJyFpWDM

>> No.31343

>>31262
wow, I just came up with that idea independently.
theirs is the same thing but better.
fuck

>> No.31348

>>31343
I hate when that happens.

>> No.31350

>>31331
damn, that thing is really stable
that's a good design; it's almost like four of those dyson "air multipliers" (fans)

>> No.31358

>>31348
>>31343
happens all the time.

>> No.31359
File: 556 KB, 2048x1536, catnip.jpg [View same] [iqdb] [saucenao] [google]
31359

what would i need to put together to end up with 2500mAh and 1.2V from 120V and 60Hz?

>> No.31368

>>31359
pic saved
you just mean mA not mAh?
wall wart and some sort of low dropout voltage regulator. The lm317s minimum is like 1.5V so you'd need something else...

>> No.31374

>>31359
a 4W resistor worked for me once. but the best thing would be a transformer + retificator. there might be other tricks around but i only know those.

>> No.31596

>>31350
I wonder how well air multipliers would work in this kind of application...