Mechanical Chopper (DC-to-AC Converter)
This project shows how a mechanical chopper can be used to change DC into AC, which can then be changed back to DC as desired.
The Relay is wired similar to a doorbell buzzer. The vibrating Relay contact interrupts the current in the circuit so that squarewave pulses of current pass through the Transformer winding. The Transformer passes the square-wave on to the other winding due to transformer action.
Because more Transformer turns are wound on the winding which feeds the Diode circuit, the voltage is stepped up to a higher voltage. The square-wave secondary voltage is rectified by the Diode, filtered by the 3.3uF Capacitor, and then the resulting DC voltage is measured by the DC voltmeter, composed of the meter and the 220K Resistor.
For a more detailed description of the DC voltmeter see Project Capacitor Charge and Discharge in Capacitor Section. For a more advanced DC-to-DC converter see Project DC-to-DC Converter in Switches Section.
This mechanical chopper was very popular before the days of Transistors, but now Transistors have replaced these in all new designs. Your parents will remember the days of the automobile radio "vibrator". The vibrator performed the function of the Relay in this circuit.