DC Motor Control using Thyristor

This undergraduate-level analog circuit demonstrates fundamental semiconductor power control using a TYN612 thyristor configured as an electronic latch. The system is powered by a 9V DC supply and drives a DC motor as its primary load. The circuit relies on the regenerative switching behavior of the thyristor, which acts as a solid-state switch. In its resting state, the thyristor blocks current flow from the 9V supply to the DC motor, keeping the motor stationary. When the push button S2 is momentarily pressed, a positive trigger current is injected into the thyristor's gate terminal through the current-limiting resistors (such as the 510 ohm and 1k ohm resistors). This gate current forces the thyristor to transition from a non-conducting blocking state into a highly conductive forward-conduction state. Once triggered, the thyristor latches ON, meaning it will continue to conduct current to the DC motor even after the trigger push button S2 is released. The only way to stop the DC motor and return the thyristor to its blocking state is to interrupt the anode current path using the reset switch S1. Opening S1 momentarily drops the main current flowing through the thyristor below its holding current threshold, causing the device to commutate and turn off. Through this arrangement, students can analyze semiconductor latching behavior, gate triggering characteristics, and manual commutation techniques in discrete analog hardware.