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DPDT Solid-State Relays - Why so hard to find?

Discussion in 'General Electronics Chat' started by DerStrom8, Jul 9, 2015.

  1. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Hi folks,

    For over a month now I have been trying to find a PCB-mount DPDT (2 Form C) solid-state relay but have had no luck. I know I can use some opto-relays wired in a certain way to do what I need, but I'm curious as to why DPDT SSRs are so rare. In fact, I don't think I've come across any in my searches. Does anyone know of a dedicated DPDT SSR, or will I have to construct one with optos (or other type of switches)?

    Thanks,
    Matt
     
    Last edited: Jul 9, 2015
  2. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Probably because solid state 'relays' aren't really a relay at all, just a fairly poor imitation, with lot's of limitations compared to a proper mechanical relay.

    Why do you want one?.
     
  3. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    :wideyed:Why not use the more common dual Half bridge with isolated drivers?

    mosfet or ... I.G.B.T.


    Can switch up to 1MW loads if you can afford them. From Mitsubishi.


    i imagine you must have HV or Inductive reasons for not using a relay, which may be the obvious choice.

    In this case, you can design a secondary spark gap switch with fly-leader breakers or HV contactors.

    A better question is how many Joules must be switched and at what insulation barrier, and V,I,Z load characteristics?
     
    Last edited: Jul 9, 2015
  4. dave

    Dave New Member

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  5. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    I need to swap two data signals based on a control input. Effectively I need a way to make the following DPDT relay using solid-state parts:

    [​IMG]

    Based on the "position" of the relay, INX will be connected to OUTX or OUTY, and INY will be connected to OUTY or OUTX.
     
  6. crutschow

    crutschow Well-Known Member Most Helpful Member

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    I believe they aren't made because of the complexity of the required circuit and the lack of demand for that configuration.

    What is the voltage and current, and do you require isolation?
     
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  7. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Can it be done with an inverter and a bilater switch (e.g., CD4016) like this:

    upload_2015-7-9_20-20-4.png

    John
     
  8. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    So you want a CMOS switch, NOT a relay :D

    Check out the various CMOS switches - the 4066 is the most common one.
     
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  9. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Ok, I guess my terminology was wrong. It functions like a relay, but is technically just a switch. This is MUCH closer! I actually think the NX3L2467 is exactly what I need!

    Thanks folks!
     
    Last edited: Jul 10, 2015
  10. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    ONLINE
    Last edited: Jul 10, 2015
  11. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    KISS, your timing couldn't have been better. I was just about to post that :D The NX3L2467 I mentioned earlier is a 3.3V device, whereas I'm looking for 5V devices. I searched and a couple of hours ago I found the NLAS44599 and was going to post it here.

    Thanks!
    Matt
     
  12. Wade Hassler

    Wade Hassler Member

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    Are these analog signals? Any reason not to use a multiplexer?
     
  13. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    They are both digital signals. I need to be able to swap their paths, hence the DPDT relay diagram I added in Post #4
     
  14. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Look at this IC, CD4503, its a tri-state non inverting buffer.
    E
     

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  15. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    This shows an option using two 74HCT244's.
    E
     

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  16. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Thanks Eric, but I don't think that's quite what I'm looking for. The second one you posted is, but it uses more components. I'll probably stick with the NLAS44599. It does exactly what I need it to.

    Thank you everyone for the help!
    Matt
     
  17. ChrisP58

    ChrisP58 Well-Known Member

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    Also look at the CD4052 and CD4053 CMOS analog switches.
    Similar parts #s are 74HC(T)4052, 74HC(T)4053.
     
  18. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Thank you for letting us know it is digital (post#12). Why not use a small, 8-pin MCU?

    John
     
  19. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Due to the nature of this project, the fewer MUCs the better. Bidirectional switches are definitely the way to go as they simply pass the signals.
     
  20. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    I don't understand that logic. Why is analog (like the CD4016) better than digital when dealing with digital signals? Please expand on that reasoning.

    John
     
  21. Wade Hassler

    Wade Hassler Member

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    upload_2015-7-10_16-48-36.png
    One chip: 40 cents
     
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