Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

I have found the small 2 pin U lamps are actually 4 pin internally with filaments. Inside the base one pin from each end of the lamp are connected together through a capacitor.

I suspect one could remove the cap and use a normal 4 wire ba1last, a series inductor with click starter or even a push button switch starter with series inductor. Got to be a billion ways to make these things work.


Here is how the two pin (with cap bulbs work) CFL bulbs work. To start the bulb the electronic balast puts out a frequency that resonates with the series cap and its output inductor. This allows current to flow through the bulbs filaments and heats the mercury vapor. Also because of the resonance there is a fairly high voltage across the cap ( big phase shift here). The high voltage eventually causes an arc to form in the tube drastically lowering the tube's internal resistance and the voltage across it from well over 100V to to less that 60V depending on temp. Once the arc if formed the tube's resistance is very low compared to the caps reactance and the cap is effectively out of the circuit. Then it's just the electronic chopper driving the tube through the output inductor to limit the current. The CFL's circuit is very crude but effective.

Ever wonder why you don't get 25 years out of the CFL's -- they are built so cheaply without any line transient protection. One overvoltage spike and it's toast.

You can actually buy a low cost CFL, hack the board out of he CFL and use it on your UV light. Just remember chopped 168V non isolated power will knock you off your chair.

Craig