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Forum Normally Closed  Relay never Opens
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Forum Thread Details
  • State Suggested Answer
  • Replies 5 replies
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Related

Normally Closed  Relay never Opens

jwmartin
jwmartin over 7 years ago

Hello,   I purchased a SS relay Crydom DC60S3-B .   I intended to use it to power a cell modem (12 volt) and need it to be normally closed, so the modem always has power.    To save power, a program controlled data logger would apply 5 volts to the relay control when the modem wasn't needed to be on.  This configuration allows me to connect to the data logger through the modem, and if changes are made to the data logger program, power is Normally applied to the modem and the connection is not lost.    The problem is that the relay doesn't seem to ever be in a open condition.     My data logger program applies 5 volts to the relay input, but power output (12 V) is still going out across the relay.  The actual voltage does drop(dropped 12.8 to 12.6 volts), but does not turn off.      Is this the wrong relay for this application? 

 

Thanks

 

-Joe

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Top Replies

  • mcb1
    mcb1 over 7 years ago in reply to jwmartin +2 suggested
    jwmartin Your drawing above shows a -5v on Pin4 and then +5v from the Datalogger on Pin3. You should have Pin4 connected to ground or zero volts. (the same 5v supply you're using to provide the 5v from…
  • 14rhb
    14rhb over 7 years ago +1 suggested
    Hi Joe, Is the coil voltage specified at ~5v ? Any possibility you can provide a few photos or a circuit diagram to help the E14 community work out what is wrong. regards, Rod
  • jwmartin
    jwmartin over 7 years ago in reply to 14rhb +1 suggested
    The relay input is 3.5-32 VDC. The output rating is 60 VDC 3Amps.
  • 14rhb
    0 14rhb over 7 years ago

    Hi Joe,

     

    Is the coil voltage specified at ~5v ?

     

    Any possibility you can provide a few photos or a circuit diagram to help the E14 community work out what is wrong.

     

    regards,

     

    Rod

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  • jwmartin
    0 jwmartin over 7 years ago in reply to 14rhb

    The relay input is 3.5-32 VDC.  The output rating is 60 VDC 3Amps.   image

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  • 14rhb
    0 14rhb over 7 years ago in reply to jwmartin

    Hi Joe,

     

    I've never used one of these solid state relays before but it looks to me like you've wired it correctly (e.g. against the datasheet here ).image

     

    I notice the datasheet mentions a minimum load current of 20mA - so if you don't have an actual load perhaps that is an issue? Add a 560R resistor to ground would meet that at 12v.

     

    The only other thing I noticed was that the specification has a flyback diode to protect the output.

     

    regards,

     

    Rod

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  • jw0752
    0 jw0752 over 7 years ago

    Hi Joe,

    The solid state relays will have some normal leakage as they are not like a mechanical relay where contacts are actually opened. If you are feeding a high impedance low current input there may be enough leakage. Try putting a larger load across your device to pull the voltage down. If this doesn't help there is a guy on the forum that specializes in SS relay questions.

     

    John

     

    Have a question about solid state relays and their applications? Ask me!

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  • mcb1
    0 mcb1 over 7 years ago in reply to jwmartin

    jwmartin

    Your drawing above shows a -5v on Pin4 and then +5v from the Datalogger on Pin3.

     

    You should have Pin4 connected to ground or zero volts. (the same 5v supply you're using to provide the 5v from the datalogger)

    This means that wehn your datalogger triggers, there will be 5v across the control (Pin 3 and Pin4) side of the SSR.

     

    A quick check is to put a LED with series resistor across Pin3 and Pin4 and you should see it light when you trigger it, and go out when it's off.

     

    Mark

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