Designing A Drive & Control Circuit for High Powered L.E.D’s

Well it has been a crazy few months with editing weddings and such however I have still managed to find time enough to design, develop and write the program for the microcontroller for my version of the now famous Ice Light.

The Design of my light had a few things that needed to be met:

1. It had to be adjustable in steps such as how photographic lighting works.
2. It had to be over 1000 lumen to make it usable on camera equipment that did not have great ISO performance. Also the light would be put through diffusion which would weaken it.
3. It had to be portable and re-chargeable and the batteries needed to be light and readily available.

Now I also did some homework and have improved considerably over the Ice Light design by using even higher quality LED’s. CRI rating of the LED is even more important than the temperature of the light. CRI is your colour rendering index and most LED gear is below 80 CRI. The Ice Light is 90 CRI and above. I have located and been testing a 98+ CRI LED and the results are outstanding. It is a 5600K 98+CRI 1 Watt LED module. You must remember that Colour Temperature can be corrected in camera or post however lack of certain colours is a little harder.

The light produced by these modules is fantastic. The colour rendering is amazing in comparison to any other artificial light source I have ever tried.

Then the project began on how to drive these LED’s as they are current sensitive devises and just throwing power on them will mean a short life for the LED. You have to limit the current to the max level that the LED specifies. In my case with test LED’s it was 12V and 900ma max. I did some testing and found the difference in light between 900ma and 700ma was marginal but the increase in heat was a lot. I therefore decided to limit myself at 700ma.

I have been building and testing various drivers over the last few weeks and have finally found something that I enjoy using. It really does simplify my task.

Then there was the LED control circuit. Sure I could just throw a variable resistor on a mosfet and use that to vary the power of my light but I wanted to make this thing better than any other light out there and one of my pre requisites was that the light could be controlled in steps. The reason for this is you could easily set two light at the same level or adjust ratios as you have preset levels.

Dont get me wrong as using logics I can give said light around 255 levels which would make it almost analogue but this would be a pain to manage for the end user.

I made up my mind to use at ATMEGA 328-p as they are readily avail and easy to program. I also used the Arduino platform to design and test but the actual end unit is a standalone ATMEGA controller with a few components around it. Why waste an entire Arduino board after all.

I ran into many many issues while playing with these circuits and also due to lack of sleep managed to blow a ATMEGA CPU and a few other bits and bobs so if you want more information on how I got this lot to work WELL. Drop me a message and ill help you out.

 

Cheers for now

 

Dionne