How does a capacitor charger circuit work in a disposable camera ? Can I build it from scratch ?

I wanted to ask this question for a long time... In every coil gun instructable there seems to be a readily prepared circuit that changes DC into AC, steps up the voltage and then changes it back into DC to charge a bank of capacitors. My guess is that the circuit contains an inverter, transformer and rectifier... Am I right?

My question is, can I build that circuit from scratch ? If yes what materials do I need ?

Thank you.

Picture of How does a capacitor charger circuit work in a disposable camera ?  Can I build it from scratch ?
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Yes it is a simple oscillator to a step up transformer I made one modeled after a flyback driver for my first coil gun. It still works good.
Flyback 1a.gifMagnetic Wire 3.JPG

Thanks for your submission. Would you mind explaining how the circuit functions? How does the feedback transformer make the transistor oscillate? What kind of voltage waveform charges the capacitor?

This circuit finds its own resonant frequency.

To look at the circuit you might think it makes a positive square wave.

It makes a more of a positive sign wave.

When the primary winding charges it creates an impedance in the feedback winding driving the transistor.

There is a little rebound in the magnetic field causing a more AC current in the secondary, the secondary passes through a diode at a higher voltage charging the capacitor.

ohhhhhh, thanks! I understand it now.

Your welcome

iceng3 years ago
Yes you are correct
Although there are great variations how the Capacitor for powering the
Rail gun is charged up to power.

The energy stored in a capacitor = C*V2/2  you can immediately see
the V voltage is the best way to store power.
You want to find 400V, 500V maybe 800V capacitors with
hundreds of micro Farads of C capacitance,

If you have time there are some fairly simple circuits that can slowly
charge up the capacitor.  Even the strobe camera circuits in your pic
can take a few seconds per flash.


Thanks for submitting. Would you mind explaining how this circuit works? What makes it oscillate? That's a bridge rectifier on the right end of the circuit, right?