Low voltage DC motor speed control circuit

Description.
Here is the circuit diagram of a low voltage /low power DC motor speed controller based on the IC TDA 7274 from ST Microelectronics. The IC TDA 7274 is a monolithic integrated DC motor speed controller intended for low voltage/ low power applications. Built in internal voltage reference voltage, wide input voltage range (1.8 t0 6V), high linearity, 700mA output current, excellent temperature stability etc make this IC well suitable for almost all low power DC motor speed control applications.
The motor to be controlled is connected between pin3 (Vs) and pin4 (output) of the IC. Resistor network comprising of R1, R2, and R3 is the section that deals with the speed control. Control pin (pin8) of the IC is connected to the junction of R2 and R3 and the speed of the motor varies linearly according to the position of POT R3. Capacitor C1 rectifies the fluctuations in motor speed and capacitor C2 cancels the motor spikes.

Circuit diagram.

low voltage DC motor speed control

Notes.

  • The circuit can be assembled on a Perf board.
  • Power supply Vs can be anything between 1.8V to 6V and it must be selected according to the rating s of the motor.
  • Maximum output current capacity of this circuit is 700mA.
  • TDA7274 must be mounted on a holder.
  • POT R3 can be used to vary the motor speed.
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20 Responses to “Low voltage DC motor speed control circuit”

  • sumit says:

    sir i want to dc motor using in my bicycal sir which rating of d.c. motor can i use, and how sped control its?

  • schalk pienaar says:

    hi i am looking for a circuit that could control the following motor(http://www.electronics123.co.za/Main.asp?D=%7B94AC31E9-6152-4976-B014-882090FCD40D%7D&PageType=Product&CategoryID=1716&SKU=AD973) with a variable resistor. i want to control the speed from zero to fairly fast. could you offer any adivice. this is the closest as i have come to an answer

  • MD says:

    Hi,
    Thank you very much for publishing this super simple but great Circuit diagram. I already brought all the parts required. But only one problem Is. I am new in Electronics. I don’t know how how to count IC (TDA7274)pins/connectors. Which one is #3,4,5,6, &8 ??

    Please help me on this I can understand this is super simple to you to know me this information.

    After Getting your information I will connect all the parts with a PerfBoard as shown in the diagram. Just awaiting for your response.
    Any help will be Highly Appreciated.

    Regards,
    MD

  • Shriraam.s says:

    Dear sir/madam previously i tested my IC by subjecting it to variable load.
    It is quite enough to control.But non linear speed achieved at first attempt.additionally i added another filter capacitor at the rectifier stage.
    after that speed comes to linear one.But iam at perturbation that is
    what kind of Filter i want to adopt in rectifier stage??
    Currently i using capacitor filter.
    shall i use TDA7275A IC by connecting it at the output of TDA7274.
    will it matches?
    please send me comments i waiting for your suggestions and queries.

  • Shriraam.s says:

    I have gotta IC TDA7274 for required level with prescribed passive components. it found more compatible and simplest circuitry.
    I given a connection and tested. Yes the speed varies linearly.
    this circuit merely avoids wow and flutter. Nice to use!!
    i have one little question will this circuit stability gets disturbed
    if i apply little variable load to the motor?
    how ever i tested this by one way. i stopped the rotating motor by
    my hands and touches the IC there is no thermal runaway. it is
    a positive sign where this IC can tolerate thermal problems.
    i like to know more things about this IC please reply to me!

  • Shriraam says:

    Thanks to ST micro electronics.I purchased Required amount of
    TDA7274 and with other passive components.I given a prompt connection
    with motor. Yes the speed get controlled and i felt better linearity with
    adjustment.this circuitry is very simple and compatible well i can
    place it in the PCB board.

  • shriraam.s says:

    Thanking the publisher who recommend this valuable circuit.
    i have a small 6V DC motor of MABUCHI brand.it serves more than 18 years. currently it’s
    speed control circuit deads. i tried to mitigate that but not able to do.
    now i got this circuit and i like to try with this circuit by replacing old ones.
    will this IC TDA7274 is available in all electronic component marts?
    if it is so please send me a comment.
    looking forward for your positive answer.

  • k.hariprasath says:

    please help for mobile using control dc motor and contact number is 9344592408 i am studying in narusus sarathy institute of technology B.E(E.C.E) 2nd year at poosaripattti omalur (tk)salem (dt)

  • vedant shukla says:

    i want to make it for our project. so what i will do? give me better suggestion. Thanku.

  • Shahabaz says:

    please someone help me out i wana make an IR-remote operated DC motor, soo that I can control its speed remotely…

  • Harry says:

    Sam,

    I can help, please contact me by mail sayang zonnet nl

  • sam says:

    i m looking for a circuit that can control dc motor speed and its direction of rotation and also i want to display the speed of the motor..plz help me m really worried about my project to be submitted very soon…

  • randell says:

    please post the explanation of the current flow on this circuit and how this circuit operates….

  • Seetharaman says:

    Hi Jay use TDA7275A which will be most suited for 12 volt DC brush type motor application
    http://www.digchip.com/datasheets/parts/datasheet/456/TDA7275A-pdf.php

  • jay says:

    give a circuit which would run the motor at (say —30%, 60%, 100% )of the maximum speed of motor……using only 12V, 1A supply transformed through 230V, 5A…

    switches are needed to switch to different speeds..

    a very very thanks in advance….!

  • Al says:

    Thanks for the circuit? Can I include a DPDT switch in this for a reversible motor?

    Many thanks in advance
    Al

  • john says:

    Hi Rolfi,
    I have sent you a personal mail. Please check it.

  • Rolfi says:

    The TDA7274 was intended mainly for portable music players, and however ingenious, together with cassette players and the like, it has been discontinued and is obsolete (See manufacturers data/application sheets: http://www.st.com/stonline/products/literature/od/1481/tda7274.pdf)

    As a general comment, though, I would like to mention that speed control of a DC motor connected to a varying load can be tricky. A stable voltage is not enough, because when a load is applied, the speed will decrease, – while the armature current increases. In order to avoid this decrease in speed, the presence of a speed regulator will increase the motor voltage enough to keep the speed virtually constant.
    Now, for this, two different strategies exist:
    1. Measuring speed and applying voltage until the speed is ”correct” (Negative Feedback control).
    2. Measuring the armature current, which reflects the decrease in speed, and increase the voltage proportionally (Feedforward control).
    The latter is the simplest and cheapest, and that is mainly what the TDA7274 does, – or did.. However, the problem here is that to much compensation will make the motor run faster, thus making the system unstable. Moreover, this type of compensation lacks the accuracy of the negative Feedback method, and it also depends heavily on the electromechanical properties of the individual motor. In the circuit diagram, R1 determines this compensation, it’s optimal value being dependent of the motor in question. A too big value will inevitably lead to instability.
    Today, in applications where speed control is essential, small motors will often be step motors, whose speed is genuinely determined by the frequency of the applied pulses, while PWM (pulse width modulation) is used for controlling the applied voltages. For a step motor, even the shaft position is easily controlled. Disk drives rely on this.

    • Shriraam.s says:

      Do any cooling provision need for this IC? because i don’t like
      My IC to get little heat up. operating with normal temperature the
      life time of device gets extended. This circuit is best suited for
      analog control also what is it’s maximum temperature?
      for what temperature range the stability will cease?
      please clarify my doubt.

  • zaeem says:

    I like it…………