Hi, so I'm having this issue with a high voltage generator circuit I've made for a DIY geiger counter.
It's the inverter circuit from an electric fly swatter. I havent traced the circuit but it's a completely standard topolygy seen in those, a 5-pin transformer, a transistor and some resistors on the input side, a series diode and a parallel capacitor on the HV side.
I've modified the output side slightly, putting a series resistor to limit current before the HV capacitor, and then a string of zener diodes and resistors to reach around 400V. A bit crusty but it has worked great so far. Problem is, I've always operated the circuit with two power sources: a 9V battery feeding the audio amp and a 7805 regulator to feed some digital logic, and 2 AA batteries for the HV supply. This is awkward though,
and now i've replaced the 2 AA batteries with a L78L33ABZ fed from the 5V reg. Now there's a HUGE amount of noise everywhere, with 50 mv ripple between the 9V battery terminals, and almost half a volt on the 78L33 output! Issue is, if I add smoothing capacitors on the 3,3V reg output, it changes the frequency of the HV inverter, easily detected because it's in the audible region both before and after.
How do I solve this? CAN i even solve this, or is the 3,3V reg just unsuitable for the purpose?
Thanks in advance.