1. #1
    Hi guys,

    I am thinking of using this solid state relay to control the motor ON/OFF signal of the Chinese VFD. Also maybe to control the Enable on each of the servos.

    RS part 720-3956

    I use 24Vdc for the control side, and I've tried this SSR with a simple LED and it switches on/off fine.

    My question is: this SSR is rated at a maximum 100mA for the load side and I have no idea what the load would be on the ON/OFF contacts of the VDF or for that matter the servo Enable, I suspect very low. Do you think this would work?

    Consequently I suppose these signal contacts would be isolated from any VDF/driver return surge on disconnect and a diode on the load side may not be necessary?

    Thanks for your advice.

    Edward

    Click image for larger version. 

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    Last edited by Edward; 07-09-2017 at 08:31 PM.

  2. #2
    It's overkill but should work, the VFD should provide it's own trigger voltage and with that all you really need is some basic support components and a suitable transistor.
    The maths and technology is very simple and the parts would probably cost pennies online, or less than a fiver from Maplin.

    - Nick
    You think that's too expensive? You're not a Model Engineer are you? :D

  3. #3
    Thanks Nick,

    This relay is quite cheap, around 6 and would just be connected straight to one of the opto outputs of my controller (they can drive up to 80V). I only chose it because it goes with my 24V limits circuit.

    Edward

  4. #4
    If you have a common zero voltage reference it will work.
    You think that's too expensive? You're not a Model Engineer are you? :D

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