I'm an amateur at electronics circuitry and concepts. I have designed a simple capacitive power supply using few web images and brief lessons. I understand that this type of transformerless power supply is highly dangerous. So i will take the utmost care while working with it.

enter image description here

The motive of the circuit is to charge a 4-4.2v battery (mAh capacity unknown) to operate a single 1 watt white LED when needed (basically a simple cheap flashlight circuit).

I tried to simulate the circuit in Falstad circuit simulator but it isn't the easiest and doesn't render at times( or renders different values at different times )

I have few questions, some of which might seem to be very simple(noobish) but please bare with me. Any kind of knowledge will be much appreciated.

Questions 1. If the mains are disconnected and the SWITCH OFF, can the battery discharge through resistor R3 then capacitor C2 through the 1n4007 Bridge rectifier and back to the negative terminal of the battery?

  1. What effect does the values of resistors R1, R2 have on the overall circuit in terms of current and voltage output at capacitor C2?

  2. Still need to calculate values for resistor R3, R4

  3. Suggest any circuit/component modifications with basic electronic components along with some explanation or information.

  4. Recommend an extensive circuit simulator with pcb design.

Thank you

  • \$\begingroup\$ this will overcharge and kill your battery. Use a proprietary charger IC. \$\endgroup\$ – Neil_UK Oct 10 '19 at 19:00
  • \$\begingroup\$ @Neil_UK i wish to build my own circuit to learn electronics practically. Also i don't intend to spend too much money on this. The battery is a cheap Chinese generic battery. \$\endgroup\$ – putu06 Oct 10 '19 at 19:07
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    \$\begingroup\$ No, please do not try this. You need to use a proper battery charger circuit. It doesn't matter how cheap the battery is, your hospital bills will be very expensive. \$\endgroup\$ – Elliot Alderson Oct 10 '19 at 19:19
  • \$\begingroup\$ @ElliotAlderson then can you suggest a circuit or design that can charge a battery but with a capacitive power supply design? \$\endgroup\$ – putu06 Oct 10 '19 at 19:27
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    \$\begingroup\$ I agree, a much more practical solution would be to use the 5v/100mA available from a USB port to charge a battery. You could try a LM317 with output at 4.1v through a suitable current-limiting resistor to a 4.2v battery. Then just plug it in overnight (or indefinitely) and should not have to worry about over-charging the battery. Easy, cheap, much safer. \$\endgroup\$ – rdtsc Oct 10 '19 at 20:41

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