Dual Relay Board

First, the board works as advertised. Thanks.

What I do not understand is:

When powered on, voltage at the Commons and Normall Closed lines are 124 volts, as measured on a DMM. But I also see just under 3 volts on the Normally Open lines. This doesn't make any sense. Any help or comments would be appreciated.

Comments

  • 6 Comments sorted by Date Added Votes
  • MikeDYurMikeDYur Posts: 1,700
    edited February 28 Vote Up0Vote Down
    Not sure what relay board your talking about, or the application your using it in. But you need to provide more information if you are looking to get any help.

    Is it a Parallax product?

    Do you have a schematic?

    What is the microcontroller your using?

    What is your application?


    People need to know the particular's.
  • Okay. This is the Parallax forum and the board is the Parallax Dual Relay board.

    No, I do not have a schematic, but Parallax does and it can be found on their site where they talk about the product.

    The microcontroller doesn't matter, as the board is all by itself in this case.

    The application might matter eventually, but as I said, the board is all by itself.

    If the board is given the 12 VDC is expects, it functions. It does nothing, but it functions. You can test for power at Commons, Normally Open and Normally Closed. I expected AC line voltage at Commons and at Normally Closed, and that is what I saw. I expected to see zero volts AC at Normally Open, but instead got a measurement of just under 3 volts AC using a DMM. I am measuring between neutral and hot.
  • Okay. This is the Parallax forum and the board is the Parallax Dual Relay board.

    No, I do not have a schematic, but Parallax does and it can be found on their site where they talk about the product.

    The microcontroller doesn't matter, as the board is all by itself in this case.

    The application might matter eventually, but as I said, the board is all by itself.

    If the board is given the 12 VDC is expects, it functions. It does nothing, but it functions.

    The board is controlled by 2 signals on J4 pins 3 and 4. Pin 3 controls K1, Pin 4 K2. The circuit controlling the relays must also share a ground connection with the relay board.
    You can test for power at Commons, Normally Open and Normally Closed. I expected AC line voltage at Commons and at Normally Closed, and that is what I saw. I expected to see zero volts AC at Normally Open, but instead got a measurement of just under 3 volts AC using a DMM. I am measuring between neutral and hot.

    That is normal operation so far. The 3VAC is line noise being picked up by the meter due to it's high impedance input. If you now put 3.3V or 5V signal on pin 3 or 4 the appropriate relay should be activated and you should measure AC line voltage on the NO and 3V or so on the NC.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • MikeDYurMikeDYur Posts: 1,700
    edited February 28 Vote Up0Vote Down
    I think you are seeing a fluke, if you are measuring between the Normally Open and Neutral, the neutral should not be connected to the relay, only the hot(black wire) should be switched. And if your seeing a small voltage on the N.O. terminal, and the relay is NOT energized, then that is negligible. But what you are switching is normally on, until the relay is energized.

    What type of load are you switching? Don't go over contact rating for the relay, or the contacts could fuse together. Had that happen once switching DC.
  • Thanks for the replies. I agree that 3VAC is negligible, but it surprised me. My thinking said that an open relay would read as 0.

    As I said, the board functions as expected, and no, the load will be far under what it can handle. I have already used the board in a protoype and think good things about it.
  • Out of curiosity, what is the AC load connected to the relay?
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