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Electronics Replace relay with transistors

Discussion in 'Modding' started by jazzzyj, 23 Feb 2013.

  1. jazzzyj

    jazzzyj Minimodder

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    Hi guys.
    I have a need for this following circuit, but it currently uses a automotive relay. I want to make it solid state, and so also quite a bit smaller.


    [​IMG]

    The 12 volt source from the left is controlled by a switch. This is driving a solenoid on the right. The square box. Solenoid has dual coils, one to "open" it (black connection), then the other to "hold" it (green connection).
    The circuit creates a pulse for 1-2 seconds to the black wire then leaves the green wire to take over. When the 12 volts is removed from the left, the circuit resets.

    Is anyone able to have a look and re-draw it to use a transistor/Mosfet instead please?
    Thanks!

    -J
     
  2. theshadow2001

    theshadow2001 [DELETE] means [DELETE]

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    Any time ive used a solid state relay it has just had two terminals which were wired in the same manner as a regular relay. Obviously using just a mosfet would require a slight modification to the circuit.
     
  3. jazzzyj

    jazzzyj Minimodder

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    I used to know about electronics, but my powers have escaped me.
    I'm sure it is simple, but I don't know how to do it.
    -J
     
  4. Boscoe

    Boscoe Electronics extraordinaire.

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    I wish I could help but I only have an iPhone or iPad this weekend!
     
  5. ferret141

    ferret141 Minimodder

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    Paint it?
     
  6. jazzzyj

    jazzzyj Minimodder

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    Its ok, its not a rush. Need it soon but it will wait til after the weekend!
    Thanks guys.
    -J
     
  7. ShinyAli

    ShinyAli What's a Dremel?

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  8. jazzzyj

    jazzzyj Minimodder

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    Na, want to do it properly.
    -J
     
  9. feedayeen

    feedayeen What's a Dremel?

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  10. jazzzyj

    jazzzyj Minimodder

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    Will a SSR react in the same way as a normal relay?
    The circuit I posted uses a cap to hold the pulse for a few seconds.
    I would rather use a transistor as it would be smaller than a SSR wouldn't it?
    -J
     
  11. Boscoe

    Boscoe Electronics extraordinaire.

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    Why use an expensive SSR which is overkill. Just use transistors in emitter follower, I will draw it tonight when I get my comp.
     
  12. Boscoe

    Boscoe Electronics extraordinaire.

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    What currents will you expect with the relay? I assume its 12VDC?
     
  13. jazzzyj

    jazzzyj Minimodder

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    Yes it's 12vdc. The momentary pulse will pull about 2.5 amps apparently.

    Thanks!
    -J
     
  14. Boscoe

    Boscoe Electronics extraordinaire.

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    And the longer one?
     
  15. Boscoe

    Boscoe Electronics extraordinaire.

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    Looking at it now I don't really understand your drawing. Here is a transistor 'switch' attached. L1 symbolizes your solenoid. attach the base of Q9 to anything above 1.5V refrence to GND and current will flow through L1 or whatever you put in L1's place. Q7 may need a small heatsink depending how long they are on with 2.5A running through it, 2.5A is really the max I would go on this. If you use a resistive or capacitive load in place of L1 you can drop D1. The solenoid is inductive so you must keep D1.

    Give me some more info and I'll see what I can do. Hope this helps.

    [​IMG]
     
    Last edited: 24 Feb 2013
  16. jazzzyj

    jazzzyj Minimodder

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    Thanks for that, but yes, I think you might have mis-understood the drawing.
    I have 2 coils.
    They share a common +12v supply.
    Coil 1 is a light draw coil and does not draw much current at all.
    Coil 2 is a heavy draw coil at about 2.5 amps.

    How the circuit should work:
    +12v is switched on.
    Both coils should energise.
    2 seconds elapse.
    Coil 2 de-energises.
    Coil 1 remains energised.

    +12v is switched off.
    Coil 1 de-energises.

    I hope that helps.
    -J
     
  17. Boscoe

    Boscoe Electronics extraordinaire.

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    Okay I'll draw something tonight.
     
  18. jazzzyj

    jazzzyj Minimodder

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    Cool. Thanks again.
     
  19. jazzzyj

    jazzzyj Minimodder

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    Any luck?
    -J
     
  20. Boscoe

    Boscoe Electronics extraordinaire.

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    Sorry I've been out a lot, give me 24hrs!
     

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