SCR DC motor speed control circuit using IC-CMOS

This is speed motor controller circuit of 12V DC motor. as SCR DC motor speed control circuit  using  IC-CMOS. You can adjust the speed of rotation of the spindle motor from 5-60 cycles per minute.

The work of circuit, The IC1-(CD4081) is nand gate ic type. It accepts the voltage from the bridge diode BD1. But there is no filter to smooth current.The other in the pin 2.The VR1, C1 and R1 is a phase shift or time delay to slow down,voltage from pin 3 to triggers pin the gate of SCR1 to work. Or conductors to the motor, causing it to rotate. Speed of the motor, can be achieved by adjusting VR1.

The power supply input pin 14 of IC1 is filtered to smooth the current, by through D2 and C2. The D1 prevents the noise from the motor. and D3 is reverse-voltage protection of motors. This can cause circuit damage. If the circuit is used with a motor that consumes more power. Heat sink should be attached to BD1, D1 and SCR1, because heat up. May cause equipment damage.

DC motor controller diagram with SCR and cmos ic

How to builds
This project is easy because use a few parts. For faster to build if we assemble this circuits in the Universal PCB in Figure 2 is components layout for guide.

Figure 2 the components layout of the DC motor controller diagram with SCR and cmos IC.

The components lists.
IC1___CD4081___CMOS Nand gate IC
SCR1___SCR-C106D or equivalent
BD1____Bridge Diode 6A 200V
D1_____1N5401___3A 100V diode
D2,D3__1N4004___1A 400V Diode.
T1_____Transformer 3A 12V
C1_____1uF 16V Electrolytic capacitors
C2_____220uF 16V Electrolytic capacitors
VR1____5K potentiometer
R1_____5.6K____1/4W resistors


  1. Daniel June 12, 2012
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