leds powered off of mx2

Delirious · Post by **Delirious** » Fri Aug 27, 2004 9:56 pm

I have 9 of these leds, http://www.lsdiodes.com/THC3/5mmred.htm , would it be possible to wire them in parallel off my mx2? I was originally just planning on using 5v from another source with a 33 ohm 1/2 watt resistor for each led.

Also i have 120mm fans that i would like to controll as well, can i just plug them into the mx2? they already have 3 pin connectors on them.

thx

Tom · Post by **Tom** » Mon Aug 30, 2004 9:22 am

It would be possible to wire up the LEDs in parallel off your MX2, but you'd need to use the high power GPO, if you plan on using 9 of the LEDs. To make the calculations refer to the post below.

http://www.lcdforums.com/forums/viewtopic.php?t=1527

You can also control your fans along with your LEDs. Make sure you have the unmodified floppy power cable plugged in to power up your high power GPOs. The maximum output you get out of a GPO is 12V and 1A.

Delirious · Post by **Delirious** » Mon Aug 30, 2004 11:40 am

Cool thx, i just sold my mx2 and bought a mx5

and assume it will work the same.

Tom · Post by **Tom** » Mon Aug 30, 2004 11:49 am

It will work the same with the mx5, except you need to plug in an unmodified floppy power cable along with the USB power to power it up.

Delirious · Post by **Delirious** » Tue Aug 31, 2004 11:31 am

So ill need to plug these into a 12v, 3 pin fan header, the only thing is im not sure if ive got the right resistor, a 15 ohm 25 watt resistor? Im goin to use them in parallel and according to this calculator, http://www.metku.net/?sect=view&n=1&pat ... /index_eng , thats the resistor ill need. Is this correct?

Tom · Post by **Tom** » Tue Aug 31, 2004 2:27 pm

If you connect 9 of the specified LEDs in series you wouldn't be able to power them up because they take 2.4V each LED. You can power them in parallel, but you would need a high wattage resistor over 7 watts. I suggest you look for LEDs that take less power LEDs.

Delirious · Post by **Delirious** » Tue Aug 31, 2004 2:52 pm

I already have the leds

so i wouldnt be able to use them with the mx5 in parallel using one high wattage resistor?

Tom · Post by **Tom** » Tue Aug 31, 2004 4:10 pm

You can use 1 calculated 15ohm resistor 7.3 watt resistor or you can use 9-120ohm 1watt resistors. The 1watt resistors would need to be in series with the LEDs. Each configuration will work.

Delirious · Post by **Delirious** » Wed Sep 01, 2004 6:16 pm

Ok i've decide its goin to be easier to use 2 strings of 5 leds in series, which equals 12v. Then just use a 3 pin splitter to put them all on one header.

Tom · Post by **Tom** » Wed Sep 01, 2004 10:39 pm

You cannot use 5 LEDs because there will also be a voltage drop across the resistor.

Delirious · Post by **Delirious** » Thu Sep 02, 2004 9:09 am

If i use 5 leds that use 2.4v each it equals 12v, and if i plug it into a 12v line (using no resistor) it wont work ?

Miles · Post by **Miles** » Thu Sep 02, 2004 9:37 am

What you have to worry about is current...If your LED is pushed beyond the limit, you will ultimately damage it. Depending on the type of LED you are using, but most are in the 20mA range. To figure out the following resistor values, simple OHM's Law needs to be applied:

R_led = (V_source - V_led) / (I_led)

R_led - required resistance
V_source - the source voltage (usually 5V)
V_led - usually 1.2V for common leds (but in your case 2.4V), but can be higher or lower, check the specs
I_led - usually 20mA (0.020 A), but again can vary, check the specs

Delirious · Post by **Delirious** » Thu Sep 02, 2004 10:19 am

they are 2.4v 80ma leds.

Tom · Post by **Tom** » Thu Sep 02, 2004 11:37 am

You can use a 27ohm 1/2 watt resistor in series with the 4 LEDs to get your circuit working properly.

Delirious · Post by **Delirious** » Thu Sep 02, 2004 12:03 pm

27 ohm would make them run at 2v right? Why use a low voltage like that?