Dimming an LED strip using a fan controller

neonraver

neonraver

neonraver

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I currently have an LED strip in my case connected by 4 pin molex to the PSU. This means that the LEDs are either on or off, but it would be nice to be able to change the brightness of the LEDs.

I don't have any spare fan headers on my mobo (and I don't really want any of the associated risks of connecting a cheapo eBay LED strip to my mobo) so I thought that I could maybe control the brightness using a potentiometer. I have found this rear slot fan controller that obviously accepts a 3-pin fan. Should I be able to simply use a molex to 3-pin adapter and hook up the LED strip giving me the ability to dial down the brightness? I'm not very electricals savvy so thought I would ask before I take the £1.81 plunge...
 
in theory yes, but not all LEDs are the same. All LEDs are dimmable but will depend on the voltage, amps etc. Most likely if the LED strip was designed to be placed inside a computer chassis then you will have no problems. However, I advise to disconnect all hardware from the PSU and run a five min test with just the led and your controller plugged in. If all goes well for five minutes then your safe to use.

Worst case scenario would be the resister would melt on the controller or the LED's would pop, neither would damage your PSU, just makes a horrible smell!

I had a variable fan controller on an old case that I used for an LED strip bought from overseas. Never had any problems.
 
If I had a modular PSU I wouldn't be so bothered about disconnecting all the hardware but with mine it would be a massive faff! I didn't think there would be too much of a problem with damaging the PSU/anything connected to it but I don't know if I would want to take the risk...
 
If the LED strip is a single colour variant then it is likely it'll respond to voltage control. However you may find the range of brightness isn't quite as good as you'd like, especially if the LEDs are white or blue as you will only have 2-3v of adjustment before the LEDs will not have enough voltage to light up. LEDs are much better dimmed using current or PWM.

£1.88 isn't much to drop on an experiment though and the likelihood of it blowing anything are minimal, even if you don't know what you are doing. LEDs are one directional so even if you managed to wire backwards nothing bad would happen, they just wouldn't light up.
 
Tealc said:
If the LED strip is a single colour variant then it is likely it'll respond to voltage control. However you may find the range of brightness isn't quite as good as you'd like, especially if the LEDs are white or blue as you will only have 2-3v of adjustment before the LEDs will not have enough voltage to light up. LEDs are much better dimmed using current or PWM.

£1.88 isn't much to drop on an experiment though and the likelihood of it blowing anything are minimal, even if you don't know what you are doing. LEDs are one directional so even if you managed to wire backwards nothing bad would happen, they just wouldn't light up.
Click to expand...

With my very minimal knowledge of electronics, I would say this is correct and controlling the current as opposed to voltage would yield better results. As stated though, not an expensive experiment so worth a try.
 
Thanks. The strips are just blue and I'm not that fussed about range of brightness, I just want to tone them down a bit and be able to turn them off completely I'll fork out the £1.88 and let you know how I get on.
 
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