SCR DC motor speed control circuit using IC-CMOS

This is a speed motor controller circuit of a 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 to 60 cycles per minute.

How does it work
To begin with, the 12V AC voltage from the Secondary transformer comes to bridge diode-BD1. It rectifies from AC (Alternating Current) to DC (pulsed DC).

SCR DC motor speed control circuit using IC-CMOS

SCR DC motor speed control circuit using IC-CMOS

This can use for DC motor and SCR1—The SCR needs to use DC to A-K lead—. Which uses just the pulsed DC only.
But we also use digital IC.

Cr: Photo Power SCR Bridgold

Second, we use one NAND gate CMOS-IC, CD4081. It requests a stable power supply to pin 14. The D2 gets the pulsed DC to filter to smooth DC current with C2-220uF.

Pin 1 gets the pulsed DC directly. And the other into pin 2. Next, The VR1, C1, and R1 are the phase shift circuit to delay the pulse DC to slow down.

After that, the pulsed DC from pin 3 to triggers the gate of SCR1 to turn on.

The working of SCR like switches on-off the pulsed DC to the motor, makes it rotate. The Speed of the motor can adjust by VR1.

If pulsed DC has a “high” state more than a “low” state. It makes more current to the DC motor, it rotates very fast.

But in the opposite way, the “high” is less than the “low” state. It rotates too slowly.

The D1 prevents the noise from the motor.

The D3 is reverse-voltage protection of motors. This can cause circuit damage.

If the circuit uses the high power motor. You need to install a large heat sink to BD1, D1, and SCR1. Because they are very hot, may damage.

Read: 12V DC Motor Speed Controller using 4011

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

Component layout of CMOS &  SCR DC motor controller circuit

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

Learn more: SCR circuit diagram

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, 0.25W resistors

PWM DC motor controller with NE555 »


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32 thoughts on “SCR DC motor speed control circuit using IC-CMOS”

  1. in DC MOTOR CONTROLLER DIAGRAM WITH SCR AND CMOS IC what would be the capacitor value for both capacitor.please give the reply as soon as possible.

  2. The output of the NAND is only two states – logic 0 or logic 1, how will this allow a continuous variation?

    Because by adjusting the potentiometer, we can only have output of NAND (Thyristor gate signal) as high or low.

    • the secret is on half wave rectification ,when goes high charge c1 when goes low discharge c1 like zero crossing regards

  3. this website is very usful for engineering student and also like me
    hello sir i need a pcb layout of speed control of dc motor by using scr or cmos ic
    pls send me its layout

    md ahshan ali

  4. I have designed circuit as per given circuit diagram;but it is not working…
    The variation in potentiometer is not controlling speed of dc motor….

  5. sir plz tel me the speed control of 12v 5a dc motor is compulary required heat sinks kadha ela connect cheyali circuits lo and rating of heat sink entha

  6. Hi
    thank you for the above circuit.
    can the circuit be up scalled to carry high voltages and current; say 250 dc at 100 A?


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