Dimmer Using UJT and SCR (MEC140E)

This article is from my book Robotics, Mechatronics and Artificial Intelligence (sold out) published in the United States. The described circuit can be used to control loads powered from the AC power grid. The circuit shown in Figure1 can be used as a linear power control for loads in the range between 12 and 48 V.

Depending on the power supply voltage, capacitor C1, resistor R1, and the zener must be replaced with components with different values. The following table gives recommended values for these components:






Figure 1    Dimmer using UJT and SCR
Figure 1 Dimmer using UJT and SCR


Because of tolerance variations among the components, particularly among Capacitors, you may need to experiment with each circuit to find the best values. The values suggested in the table are average.