High voltage generator
The purpose of this project is to consider how high voltage can be generated by the interruption ot DC current such as is done in automobile ignition systems. Of course the "high voltage" generated in this project is only representative and so low in value that is it perfectly safe.
The circuit includes a Speaker which will be your reminder that the circuit is operating. The Relay is connected like a doorbell buzzer. The HV (high voltage) generating part of the circuit is composed of the 470uF Capacitor and the Output Transformer.
Because the HV generator is in parallel with the Relay field coil, it also receives pulses of voltage as the Relay contacts open and close. The current to this part of the circuit quickly charges the 470uF Capacitor. This charging current must pass through the Transformer speaker-winding and the Speaker.
The current that passes through the Transformer winding induces a voltage in the second winding due to a transformer action. The amount of increase in voltage is directly related to the ratio of number-of-turns on the high voltage side, to the number-of-turns on the Speaker side.
In real HV generators this ratio is made very high. As the Relay points open, the Capacitor discharge current also flows through the Speaker and Transformer winding, but is of lesser consequence because it must flow through the Relay at the same time. This may not be able to fire a spark plug or cause a shocking experience, but it gets the point across. You will no doubt want to experiment with this circuit. It can be made to generate higher voltages. Have fun!