DIY 12v Dimmable Power Compact Driver

Posted on Feb 6, 2014

The lighting hood of AquaOne AR-320 tank. These small tanks generally come with crappy tubes with low power output and an algae-friendly colour spectrum. There are numerous ways to improve the lighting such as replacing the hood with a metal halide pendant, or dropping in some strong LEDS, but I chose to stick with the tried and tested 10, 000K/Actinic 50/50 flouro tubes since I`ve used them before and know they work.

DIY 12v Dimmable Power Compact Driver
Click here to download the full size of the above Circuit.

I also wanted to be able to control the brightness of the lighting from a separate DIY controller (ie. simulated dawn/dusk). This isn`t very easy to do with mains-powered designs, but I found that many 12v circuits are inherently suited to varying the tube`s brightness by simply regulating their supply current. This project is one of the simplest solutions I could think of to achieve my goals, and as an added bonus there is no "mains" wiring, so it`s probably legal for us non-electricians to do as well. The only changes I made to the aforementioned circuit were the transformer (i wound mine on a ferrite rod with different windings), the mosfet (i used a 30n20 which was a free sample from ON Semiconductor but similar to the one used in the example), and a mosfet driver chip (MAX4420, another free sample) which I added to the circuit to switch the mosfet fast and keep it from getting hot. Winding the transformer is a crucial part of the project. I found that with too great a turns ratio between the small and long winding the circuit runs at a lower voltage (otherwise current draw will get out of hand) and with too small a ratio, the tube may never fire at all on a 12v supply. 53:360 worked well for me, but I started with a ratio of more than 80:360 then gradually unwound the primary coil until the circuit would fire at 11 volts (which happened to be at 53 turns). The 2 Ohm resistor is in there for testing or running from a...

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