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Thread: Solid state relay

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  1. 05-06-2006, 12:20 AM #1
    N4NV
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    Solid state relay

    I purchased a Crydom D1D40 DC-DC Solid State Relay from e-bay. I am not sure that I hooked it up properly because it is always closed. There is output terminals labeled 1 +2, 100VDC 40A, the input terminals are labeled 4 +3, 3.5-32Vdc. Terminals 1&2 are always closed. When I add 5V to terminals 3&4 nothing changes. I have my +60V to the +2 terminal and terminal 1 goes to my + terminals on my Gecko drives. What am I missing?
    Vince
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  2. 05-06-2006, 12:57 AM #2
    Al_The_Man's Avatar
    Al_The_Man
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    According to the sheet I have the 4 term is - and the 3 term is + input voltage, but regardless the output should be open, are you using a high enough load as if it under the leakage current rate then it will show some conduction.
    What kind of load do you have on it, what are you actually switching?.
    Al.
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  3. 05-06-2006, 02:45 AM #3
    N4NV
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    The data sheet I found says min of 20mA load for it to switch. I have about 2A at start up, more when running and the bleeder resistor has at least 50mA if all the Geckos were off. I have the input hooked up correctly, I double checked. If there was no input, shouldn't the output be open? I have never used a solid state relay before so I am not sure how they are supposed to work. I thought they would work just like a normal relay, open contact until the control voltage is applied.


    Vince
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  4. 05-06-2006, 04:22 AM #4
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    Al_The_Man
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    Yes, if you open up the input it should turn off. Measure the DC resistance across the output with a digital type meter and if it is low resistance it is probabally shorted.
    Al.
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  5. 05-06-2006, 06:19 AM #5
    ViperTX
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    Well it's not a true relay....so open is rather misleading....the output is most likely an SCR which is a solid state device......the best way to test is hooking up a DC source with a DC lamp to one of the output terminals and the other ouput terminal to a resistor that is connected to ground....It is also important to note if the output is really an SCR the only way to turn it off is to remove the DC source from the output......it would be nice if you attached the data sheet for the part....that way we wouldn't have to look it up.....which I have not done.....
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  6. 05-06-2006, 03:27 PM #6
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    The output is Mosfet so it should turn off with no input, it would hardly be a practical switch if it stayed latched on.
    If the input is removed totally the mosfet should turn off.
    Al.
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  7. 05-06-2006, 04:20 PM #7
    joncollins
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    Hi

    The input is opto isolated so you need some volts and a bit of current to turn on the led. If the output is 'switched on' with no input connnected, my guess is that the unit has 'blown' and gone short circuit.

    Jon
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  8. 05-06-2006, 04:35 PM #8
    N4NV
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    I have attached the data sheet. This solid state relay had a closed output from the get go. I don't see how I could have blown it since the only way I have wired it is how I said in the previous message. I guess it could have been bad from the start.

    Vince
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  9. 05-06-2006, 05:03 PM #9
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    As I mentioned earlier, it looks like you had the input reversed, but that should not have affected the output, If you check the output for resistance, cold, then it should be high resistance. Low resistance if shorted.
    Al,
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  10. 05-06-2006, 05:12 PM #10
    joncollins
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    Was it new from ebay, or ex-equipment?

    What did you switch with it? did you see the bit in the data sheet about transient protection? if you switch inductive loads like motors, solonoids etc. the turn off transient can knock out the fets. so you need the 'free wheel' diode?

    Jon
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  11. 05-06-2006, 05:23 PM #11
    N4NV
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    I have only hooked it up with the - on terminal 4 and + on terminal 3.

    Vince

    Quote Originally Posted by Al_The_Man
    As I mentioned earlier, it looks like you had the input reversed, but that should not have affected the output, If you check the output for resistance, cold, then it should be high resistance. Low resistance if shorted.
    Al,
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  12. 05-06-2006, 05:26 PM #12
    N4NV
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    It was new not ex ex-equipment. I saw the note about inductive loads. The motors are connected to the Gecko drives and I am switching the power to the Geckos, not the motors directly. I thought since I was not switching the motors dircetly, I would not need the diode. Maybe I was wrong?

    Vince

    Quote Originally Posted by joncollins
    Was it new from ebay, or ex-equipment?

    What did you switch with it? did you see the bit in the data sheet about transient protection? if you switch inductive loads like motors, solonoids etc. the turn off transient can knock out the fets. so you need the 'free wheel' diode?

    Jon
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  13. 05-06-2006, 05:39 PM #13
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    Al_The_Man
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    Quote Originally Posted by N4NV
    I thought since I was not switching the motors dircetly, I would not need the diode. Maybe I was wrong?

    Vince
    Its always good to err on the side of caution, if the type of load is uncertain.
    Al.
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  14. 05-07-2006, 06:19 AM #14
    ViperTX
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    Well the Geckos should have the back EMF diodes.....I would suspect that the SSR was bad from the getgo...
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