Figure 1 – Protecting with a diode
The on and off switching process that occurs when small dc motors function can make it necessary to use some additional parts to avoid turning off of the SCR after it is triggered by short pulses. Figure 2 shows some solutions to this problem.
Figure 2 – Controlling motors
In Figure 2a, a resistor intended to maintain the holding current in the circuit avoids the SCR turnoff when the current falls to zero as the coils are switched.
In 2b, we use a diode, and in 2c a capacitor. The reader must conduct experiments to find the correct solution for each case.
