AC Motor Speed Controller using U2008B

  • Rajkumar Sharma
  • 29443
  • medium
  • Tested


This is a low cost, current feedback phase control AC motor driver based on U2008 IC. The U2008B is designed as a phase control circuit in bipolar technology. It enables load-current detection as well as mains-compensated phase control. Motor control with load-current feedback and overload protection are preferred applications.


  • Supply Input:  230V AC
  • Load: up to 500W (Triac Requires Heat sink for Higher Load)
  • Jumper J1 Selection: A-Load Current Compensation or B-Soft Start
  • PR1: Preset for Phase Control ( Ramp Current Adjustment)
  • P1 : Potentiometer Set Point



Parts List


U2008B Datasheet




  • Ajay Desai

    I would like to know the cost of this kit and it’s availability details.

    2 years ago
    • admin

      How many pieces of this kit do you need? You can also check on for kits of our projects.

      2 years ago
      • Ajay Desai

        I need about 25 pieces. It is not available on koteq. Let me know availability in Hyderabad

        2 years ago
        • admin

          Unfortunately the IC isn’t available and we cannot sell this kit.

          2 years ago
      • kamaleu norbert

        need 10 pcs of this speed controller

        8 months ago
  • Marcel

    Soft start does not work properly even with resistive load. Counter-effect. It starts at full speed and then turns to the set value of P1. Direct launch does not work at all. Could the problem be in U2008?

    2 years ago
  • this schematic isnt for load current compensation… if you look at scheme in datasheet, you ll see that its for soft start

    2 years ago
  • Sam

    is there a way to control this by Arduino, so that It can give us different speeds at a programmed time ??

    11 months ago
    • I am not sure i understand what would you like to do. Could you please explain?

      11 months ago
    • David Reynolds

      Given that a potentiometer controls the phase angle I would say that it would work from arduino. You would need to isolate the arduino with an optocoupler transistor use variable PWM to feed the opto led, and use the output on to pin 3 leave the C4 in place and put a pull down resistor in the opto output to pin5, I guess between 1K and 10Kohm.
      Do not forget it is very dangerous messing with mains voltages, do not do it if you are not sure.
      Dave R.

      10 months ago
  • Claudemir Vernini

    How can I adapt this circuit to a voltage of 127 volts, being Neutral and Phase?

    4 weeks ago
    • David Reynolds

      Reduce the R1 resistor to around 11K if you are only using 115V.AC.

      Dave R.

      3 weeks ago
  • Claudemir Vernini

    Thank you so much, Dave. Your help is of great value.
    I want to get the components as soon as possible

    3 weeks ago
    • David Reynolds

      Claudemir, if you are building the circuit on your own board, you could use a reactive feed to power it.
      By replacing the R1, power resistor with an X2 RC cap of 0.22uFx100 ohm and placing a diode across it facing the opposite way to the D1.
      This would reduce the heat wasted in the resistor. I have used this method for other mains control chips, in the past.
      Just a thought.


      2 weeks ago
  • Claudemir Vernini

    Hi Dave!
    It’s noted!
    I ordered the U2008B from China, since in Brazil it’s hard to find at a modest price.
    It should arrive around two months …
    In the meantime, I will make a new PCI card according to your suggestion.
    Thank you very much.

    2 weeks ago

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