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/diy/ - Do It Yourself

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475460 No.475460 [Reply] [Original]

instead of buying some case led's that look trashy I decided I am going to install a single (like 3mm) led in my computer case and use a molex periphery connector as power (pic related) obviously I need a resistor to turn 5V 25amp into something more suited for led but what other protection do I need to make sure I don't fry my PSU and computer

>> No.475473

>>475460
Why do you want to increase the power requirements of your computer, and by doing so reduce the overall efficiency and create more heat? All those LED's don't even look cool, they just make it look like it's owned by a geeky teenager. In any case why don't you search the catalog for /diy/, the question of how to power an LED only comes up about 20 times a day around here.

>> No.475480

you dont need anything else. just make sure the red wire connecting to the resistor is well covered up in heatshrink or tape,so it doesnt short to ground.

>> No.475576
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475576

Use heat shrink tubing at the connections. If your paranoid, you could add a fuse.


Get specs for LED. You need If(forward current) and Vf (forward voltage)
Just making them up...
Vf = 2.8V
If = 25mA

Add a 20% safety factor for If
25mA * 0.8 = 20mA = 0.02 Amps

Vr = V - Vf
Vr = 5V - 2.8V
Vr = 2.2V = Voltage drop for resistor

R = Vr / If
R = 2.2V / 0.02A = 110 ohms

Since you prolly want it bright and it will be easy to replace, round down to 100 ohms

double check using 100 ohms
If = Vr / R
If = 2.2V / 100 ohms = .022A = 22mA = not the 20% safety you wanted but prolly fine.

>> No.475635

>>475473
1) I have 750 W to play with I'm not worried about power requirements
2) I beleive a single dim LED won't look ricey, if it does I'll remove it
3)I'm not looking for powering and LED I am looking for extra safety precautions behind powering an LED (as odd as that is)

>> No.475757

Use 3V3 branch (orange wires) and you won't need resistors

>> No.475786

>>475757
Only 3v I know of is off of mobo power, which I ain't touching, hooked it up to periphery w/ resistor and works good

>> No.476042

new question one led didn't get as much light as I wanted, how to I put 3 in parallel (and where can I learn basic electronic circuits)

>> No.476118

you put 3 in parallel by putting them in parallel, but for reasons I'm too lazy to go into, they should each get their own individual current limiting resistor.

or you could put them in series, so you'd only need 1 resistor, by powering from the 12V line (yellow).

>> No.476216

>>475786
SATA power supply has also 3V3 wires, basically all orange ones are 3V3.
But resistor is also good.

>> No.476273

>>475757
enjoy your charcoal

>> No.476351

>>476118
in series is what i meant, see I know nothing about circuits, I took two chem classes in HS with one physics that only focused on mechanics, I understand the concept of voltage and current...thats about it, any resources (I'm going into electrical engineering and its pathetic I don't know this shit))

>> No.476361

OP just go to autozone or something and buy car leds. theyll already have resistors wired up to run off 12v

>> No.476447

>>476361
>not just spending 10 minutes to learn basic circuits and buying cheap leds and resistors somewhere else