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using solid state relays with servos

Discussion in 'Sensors and Actuators' started by mikgol, Nov 4, 2015.

  1. mikgol

    mikgol

    87
    1
    Jul 6, 2013
    Hi there,

    I'm using an MG995 servo, which is rated at 6v. To power it, I'm using 4 (new) AA batteries, which should provide 6 volts. The servo only comes on periodically, so to stop the batteries from going flat I've hooked up a solid state relay to turn power on/off to the servo.

    The servo is running very weak (with fresh batteries) - is it possible that the solid state relay has a voltage drop or something that's causing this?
     
  2. bigone5500

    bigone5500

    712
    120
    Apr 9, 2014
    You could probably measure the voltage to the motor as it is running. This would show if you have voltage drop. I would think that a solid state relay would definitely have a small amount of drop.

    Do you have a part number to the relay you are using?
     
  3. mikgol

    mikgol

    87
    1
    Jul 6, 2013
  4. bigone5500

    bigone5500

    712
    120
    Apr 9, 2014
    I think I could be wrong about measuring the voltage drop. However, your relay has transistor output. So I am not sure about how much drop there will be in your circuit. I'll take a guess and say not more than .5 volts.
     
  5. bigone5500

    bigone5500

    712
    120
    Apr 9, 2014
  6. mikgol

    mikgol

    87
    1
    Jul 6, 2013
    I've got the 5v version. Hmm, judging by that post I'll try putting a 1n4007 diode across it to see if that helps.

    Is it "bad practice" to use solid state relays to power motors etc? (sorry if that's a dumb question)
     
  7. GPG

    GPG

    452
    66
    Sep 18, 2015
    There's a max voltage drop of 1.5V in the datasheet.
     
  8. mikgol

    mikgol

    87
    1
    Jul 6, 2013
    Ahh yep! I see it now :) That would explain it then. I'll chuck in another AA battery to compensate. Cheers for the help guys
     
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