DIY LED Using 10 Watt Arrays

[mike31154]

Originally Posted by Tony Ooi

In the end, you didn't have any resistor in series with each LED, right?
The whole circuitry is just the 12V power go into the dimmer and from dimmer go to the LED. Please correct me if i am wrong.

You are absolutely correct. The two 12 VDC power supplies have a limited range of adjustment via a small potentiometer next to the wire terminals. The adjustment range is from about 10 volts to 13 volts. Downstream of the power supplies are the manual dimmers which provide further control & enable me to dim all the way to off.

The LEDs are all hooked up in parallel, no series chains whatsoever. If one of the LEDs were to burn out, the remainder on that dimming circuit would likely run at a slightly higher current which poses a certain risk if I don't notice for a while. I mitigate that risk by having the manual dimmers adjusted to 8.5 VDC, which is 1/2 volt below the recommended minimum forward voltage of my 455nm Royal Blue LEDs (spec for them says Vf should be 9 to 10 volts). So in essence, I am slightly underdriving the Royal Blue LEDs. The whites, 10000K & 6000K as well as the 470nm blues can handle a higher Vf (up to 12 VDC) so they are underdriven even more. In addition, each LED has its own fan for cooling, which adds to the safety factor with respect to burn outs.

I opened up a couple of the dimmers to see what makes them tick since there is little info on them other than the rated input/output. Some of the vendors selling them on eBay talk about them being pwm and/or constant current capable but it sure would be nice to confirm how they really work. Aside from the potentiometer, the dimmer consists of solid state circuitry including what looks like a MOSFET transistor, so they do have some complexity. Despite the low price, the soldering & assembly are very good quality.