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Thread: Electronics

  1. #1
    Moderator ShipWreck's Avatar
    Join Date
    Oct 2004


    I am trying to contruct a low water level shutdown circuit that was posted on RC. I have put it together but it doesn't seem to work correctly. I have never used a full wave brige multiplexer before so this may be where I am having problems, when I measure the DC outputs it seems I am getting 100vdc. I am using a solide state 3-24vDC coil relay as specified in the instructions. I have confirmed that all the wires are connected correctly.

    Any electronics help would be helpfull. I have attached the schematic I am working from.

  2. #2
    Senior Member
    Join Date
    Jul 2004
    I think one or two capacitors are missing after the bridge. Without the capacitors, the DC out is not really DC but just some half sine waves.

    I may be wrong as I haven't touched electronics for ages.

  3. #3
    Moderator cres's Avatar
    Join Date
    Jul 2004
    So, what behaviour are you seeing?

    Does the relay close when you push SW2 ? Does it close then open as you release?

    Is SW1 closed (i.e. not indicating a low water scenario) ?

    As wired, the outlet should go "live" when you press SW2 (this is the starter switch). If the rest of the circuit is correct, the outlet will stay live until SW1 opens (low water case).

    If the rest of the circuit isn't working, the outlet will only be live when SW2 is pressed.

    Apoon: capaciters might help, but, it is going through a coil which should damp the waves a bit.
    Sarchasm: The gulf between the author of sarcastic wit and the person who doesn't get it.

  4. #4
    Moderator ShipWreck's Avatar
    Join Date
    Oct 2004
    SW 1 is definately closed as I am using a jumper currently.

    When I use SW2 I get 120vAC at the receptacle and the pump will run. As soon as I let go it will stop so there must be something wrong with the DC circuitry.

    I have posted a picture of the SSR to ensure that this is a good choice.

  5. #5
    Senior Member Aqua's Avatar
    Join Date
    Jan 2004
    Problem is that Solid State Relay is not Coil Relay. SSR is relay that use electronic instead of mechanical means for load switching. They donít have mechanical parts that are doing switching and they are used in logical circuits for switching ON and OFF.
    What you need is REED RELAY that has a coil and mechanical part doing switching.
    Your measurement is righ and you donít need any capacitors for it to work properly, just get 110 DC REED RELEY and thingy should work.
    Whole thing can be much simplified by using 110AC REED relay that doesnít need bridge BR1 and wouldnít be any less safe then in the drawing.
    Since it is hard to figure out what you would like to achieve from either drawing or description it would be much efficient to describe what and how you would like to control and we can post our solution to the problem.
    Note: Circuit posted will do just opposite what you described it should.
    Man that goes to bed with itchy butt, wakes up with stinky finger!

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