could someone help me? I am modding my xbox 360 with fans and lights with an external power source and a probelm occurs.

the power source is 12 volts and 300 miliamps. all the LEDS except 1 run at 3 volts the other runs at almost 4 volts. the 4 fans connected to the power source run at 12 volts

my problem is when I connect the 4 volt LED to the circuit the_ 3 other lights will light up and do the light show the 4 v LED provides and then the lights shut down or 3 other lights will light up and do the light show the 4 v LED provides and then the lights will flicker violently or_ nothing will happen

these 4 lights are the last thing I have to do

if you have any suggestions please write back


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frollard8 years ago
the 4 leds could 'reasonably' be run in series at 12v. Voltage drop in series would be 3+3+3+4 = 13. Most wall-wart power supplies put out more than their rated voltage anyway - check with a multimeter.
**these numbers assume you want 20 miliamps for each led.

Safest bet - run the 3 3v led's in series (9v drop) meaning you need a series resistor of ~150ohms to drop the last 3 volts. Connect this string directly to the 12v
Run the 4v led with a ~400 ohm resistor in series , also connected direct to the 12v, parallel with the first string
Run the fan connected in parallel again.

All should be hunky dory assuming you don't exceed the rating of the power supply. Best to test the LED's before they're installed.
purduecer8 years ago
Instructables is reasonably good about being an open and excepting community, so hate mail should not be a problem. (If it is, however, you can simply use the flag button, which will tell the higher ups to look at any particularly unkind comments). That said, a few details are needed about your circuit. Namely, what configuration are all of your parts hooked in? (Series/Parallel) Also, if you would be so kind, use a multimeter (if you have one) and measure the current draw through one of your fans, and let me know what that is. Thanks, Purduecer
fastcar123 (author)  purduecer8 years ago
well thank you for your information on this website. The 4 lights i'm wireing are in series as for the fans they are in parallel I also have a question. what is a multimeter? I dont think I own one however the lable on the back of each fan say that they run at 12w and 0.19A please write back and tell me f that was any help
A multimeter is a combination voltmeter, ammeter, resistance (ohm) meter, and sometimes has a few other functions (diode, continuity, transistor tester)
They sell from anywhere between 5 and 500 dollars.

The fan is 12Volts (voltage=pressure), at 0.19Amps(Amps=current flow), meaning it's 12x.019 VA, or 2.28 Watts. (Watts = Power)
fastcar123 (author)  purduecer8 years ago
thank you very much I will probably go with your idea of 3 3v leds other than the 4 leds it will run fine so thank you again