Installing LEDs to Computer via PSU

Flashlight Modding and DIY Parts
1

I am not sure where to ask this so if I’m at a wrong section please help me out.

I have 2 of these 10W LEDs
I’m curious if I need any drivers to drive these lights as I am planning a direct drive straight from the PSU to light up the insides of my PC tower.

My plan was to have a configuration of using just a guitar potentiometer I had laying around to act as a dimmer for my LEDs inside.

What I should worry in the process of adding this to my computer? Do I need a 12v driver/regulator? I have 2 MR16 drivers but I was planning to skip that.

2

Holy cow, they are only 42 cents each in quantities of 10!

3

I may be wrong but that power supply should be voltage regulated, LEDs need current regulation

4

A constant current driver will be needed to use the guitar pot to control the current regulation. The Meanwell LDD buck regulators (700ma or 1000ma in wired version) would probably work? No detailed LED datasheet to know for sure. The “speculation” is based on whether the LED would be sufficiently bright based on the buck regulator voltage overhead. The Meanwell datasheet says there is a 3V differential between input and output. So the PSU 12V rail input will lead to a 9V output, and therein is the dilemma.

A resistor voltage divider (+ the pot) off of one the supply rails would need to be calculated so that a minimum 0V to 2.5V+ is wired to the driver analog dimming input.

Sizeable heatsinks required for the heat dissipation of the leds.

5

Non scientific but functional response —-> I don’t know what the guitar potentiometer looks like but I’d set it to the highest resistance, then connect the LEDs for a split sec to see how bright they are. If dim, safe. If blindingly bright, they may burn out if left on even if heatsinked.

6

Be wary trying that, most potentiometer’s are not designed for high current, they are for the adjustment of a voltage regulator circuit therefore are only designed for low voltage and very low current applications (as in 1~2ma).

I can smell the magic smoke now :stuck_out_tongue:

Cheers David

7

seems like an out from PSU is going to be too much current for these LEDs.

I was keen to sacrifice one of the empty fan slots for these LEDs to go with as I doubt PC fans uses 12V power with high amps. Plus they’re PWM controlled.
Never tested. Didn’t wanna risk anything to start.

Guitar pots are generally 250KΩ and 500KΩ so I guess it is more than enough to mild loads from PSU without burning itself? Sadly mine had no current ratings on how much they can hold

8

Have you considered using the 5v rail of the PSU?

9

I did considered the 5v rail but most of my 5v are completely used by my case usb slots alone.
Well not like I can use them with these 12v LEDs unless I make a purchase for a boost driver and lose USB power

I have also considered wiring a few of my xpe from the 3v out but I rather make full use of these 12v LEDs first

10

i had 11.9 V on a old pcu and this led worked fine!

i would not hook it up directly to 13+ Volt :wink:

11

The lower voltage rails generally put out higher amps on PC power supplies

12

How bright do you want the inside of your case to be? I would think 2 of those emitters would light up if connected 2S to a 12v rail. 2S, if they light up at that low a voltage, will help limit current due to the Vf curve of the emitters.

13

If that is the case then when you try to adjust it you will blow both the Pot AND the LED. 250K is way way too much resistance and by the time you reach a low enough resistance to start the current flowing in the LED you will be at the far end of the adjustment of the pot. At that point both the pot and LED will fry
Put another way, if you were to pass just 10mA through all of the 250K pot, you would have to dissipate 25 watts.

When you first mentioned a guitar pot, I thought maybe you were going to use a pot for a guitar speaker, or an L-Pad. Those are usually around 16 Ohms.

14

You already have the MR16 driver, why not try them out first anyway?

I have one using 350mA 12V setting MR16 driver, same LED. So bright, I fixed it as mule outside of the house at night to prevent burglary. Even at about 4W the light is very usable.

Now for your use as pimpin’ your PC, I think it will be more than adequate.

15

I’ve plotted Vf curve for this LED before. I finally found it.

Vf is 8.33V at 0.1A, and 10.75V at 3A. That’s the max you should run it with heavy cooling.

So a constant 12V voltage supply with sufficient power will definitely push it well above 3A and fry it.

16

Thanks so much for the math. I never knew it could have so much burning power.

I’m guessing this is my path to starting my mods. Should be the most simple and safe path for me.

Thanks so much all of you for guides and advices.

17

Yeap, good starting point. FYI MR16 driver current can be modified by the changing the resistor on the board.

Also take note of diminishing return. These cheap LEDs are efficient at low current but go downward fast. See example below:

Current
0.1
2.0


See at 2A, that’s 20x the current but only 10x gain in lumens.

18

got my lights ready!

it was too bright with single die and it heats up my pc case (I had my case as heatsink)
Thought it would be a bad idea so I’ll drop it by half with series based on ImA4Wheelr ’s advice

works pretty well but probably need different mounting socket. The 4 pin peripheral power cable doesn’t exist in my current psu (silly me. didn’t check before soldering them)

gotta get a 6 pin PCI Express power cable when I go shopping

19

Cool. Thanks for trying that out and reporting back. Looks like you have one Warm White and one Cool White emitter. Going for some broad spectrum lighting while you're at it?

20

gotta get the colors right mann XD