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  • Relay wiring

    I can't believe I'm asking this but I am unable to get my relays working

    This is pretty simple stuff so I hope it's not me doing something stupid, but it's likely I am

    The relays (purchased with my FB) have 3 spade connectors

    COM (common)
    NO (normally open)
    NC (normally closed)

    My understanding and expectation is that if I have a working circuit (lets say a light bulb) and I take the wire providing 12v and put the relay in series, I can turn it on and off. Like I said, simple stuff (baby steps).

    So I connected one end to COM and the other to NO. When I trigger the output port on the FB, the led lights, the relay buzzes, but my bulb never turns one. I have verified there is no voltage with a multi-meter. The NC side is always hot. I have tried 3 relays and don't expect this to be a hardware issue as they all behave the same way.

    What am I doing wrong? Is it that the relay isn't really engaging? I have looked at the FB4 manual and tried all 4 possible jumper combinations for P13 if keeping the jumpers in the same orientation as shipped and there is no difference (I have 12v to P1).

    Thanks,
    charles

  • #2
    The relay shouldn't buzz, it should just click... sounds like either bad relay, or not enough juice to the coil side of the relay.
    Tidder

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    • #3
      you do have it grounded too right? Just making sure...

      Also what power source are you using to power the FB?
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      • #4
        I am just bench testing right now.

        I'm using a power supply from an old hub/switch that puts out 12V DC (800mA). I assumed this provides ground as well. I'll try hooking it up to a car battery.

        thanks,
        charles

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        • #5
          Originally posted by cgalpin View Post
          I am just bench testing right now.

          I'm using a power supply from an old hub/switch that puts out 12V DC (800mA). I assumed this provides ground as well. I'll try hooking it up to a car battery.

          thanks,
          charles
          No I meant on the relay side. Nothing would work if the wall wart wasn't grounded!

          Basically without the relay, does the light work? It should always be on. Then cut one of the wires and put the relay between it.
          Fusion Brain Version 6 Released!
          1.9in x 2.9in -- 47mm x 73mm
          30 Digital Outputs -- Directly drive a relay
          15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
          Buy now in the MP3Car.com Store

          Comment


          • #6
            Yes the circuit works fine before I introduce the relay, LOL. I do feel pretty stupid right now, but honestly I'm not THAT stupid

            No difference powering the FB from a car battery - relay whines. What's the max voltage I can apply to the relay trigger pins to test it directly (without the FB)?

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            • #7
              Originally posted by cgalpin View Post
              Yes the circuit works fine before I introduce the relay, LOL. I do feel pretty stupid right now, but honestly I'm not THAT stupid

              No difference powering the FB from a car battery - relay whines. What's the max voltage I can apply to the relay trigger pins to test it directly (without the FB)?
              The 12v wall wart you are powering it from should be enough to trigger the relay by itself.
              Fusion Brain Version 6 Released!
              1.9in x 2.9in -- 47mm x 73mm
              30 Digital Outputs -- Directly drive a relay
              15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
              Buy now in the MP3Car.com Store

              Comment


              • #8
                Originally posted by cgalpin View Post
                I take the wire providing 12v and put the relay in series
                You connect the relay coils in series? If that's the case, each coils is getting way less than 12VDC (voltage/#of relays), so coil does not make enough magnetic field for the relay contact to move.

                Did you test each relay individually?

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                • #9
                  No probably bad choice of words on my part. By series I meant I introduced the relay into the starting circuit by "cutting" one of the lines.

                  Testing with a single relay.

                  My circuit is simply this

                  12v -- bulb -- ground WORKS!

                  12v -- COM -- [ relay ] -- NO -- bulb -- ground BULB NEVER COMES ON

                  12v -- COM -- [ relay ] -- NC -- bulb -- ground BULB NEVER GOES OFF

                  I have bypassed the FB and still have the same behaviour though when applying 12v to the trigger pins. Totally stumped....

                  The only difference I noticed with the FB is I hear a hum when the relay is turned on. With direct 12v I hear a very soft click (but have to put my ear close to it to hear it)

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                  • #10
                    try this
                    http://electronics.howstuffworks.com/relay1.htm

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                    • #11
                      Although the pettiness of my problem can't be confidence inspiring, I really do know how a relay works. Now it's certainly possible I am not connecting to the right connectors, but I don't think so. If you want to look at a reference that is a little more relevant to this problem (given the relay marking I have) please look at this and let me know what you think.

                      http://www.kpsec.freeuk.com/components/relay.htm

                      The relays I have are triggered by 2 wires soldered to the bottom - hard to screw that up if I do say so myself. I started off triggering this with a FB but have also applied 12v (and ground) to them directly with no better results. These are not shown in my diagrams.

                      For the rest of it, the page above matches it pretty well. I have 3 connectors, COM, NO, NC, which I expect to work as described.

                      2k1Toaster, do you see any problem with the way I am testing or have these wired up?

                      thanks,
                      charles

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                      • #12
                        Trigger pins are electrically insulated from NO, COM, NC. You also need to provide power source to the bulb

                        EDIT: what type of relay is it? Any model number?

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                        • #13
                          Originally posted by cgalpin View Post
                          No probably bad choice of words on my part. By series I meant I introduced the relay into the starting circuit by "cutting" one of the lines.

                          Testing with a single relay.

                          My circuit is simply this

                          12v -- bulb -- ground WORKS!

                          12v -- COM -- [ relay ] -- NO -- bulb -- ground BULB NEVER COMES ON

                          12v -- COM -- [ relay ] -- NC -- bulb -- ground BULB NEVER GOES OFF

                          I have bypassed the FB and still have the same behaviour though when applying 12v to the trigger pins. Totally stumped....

                          The only difference I noticed with the FB is I hear a hum when the relay is turned on. With direct 12v I hear a very soft click (but have to put my ear close to it to hear it)
                          If you wire it 12v -- com -- no -- bulb -- ground and then power the relay
                          coil from the 12v direct (no arduino at all) and the bulb doesn't come on...
                          then quite simply the relay is goosed!

                          Or it's some mad relay that needs huge voltage across it's coil.....

                          C
                          The Wolf - Winner DC08 'Most Ghetto' Award

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                          • #14
                            Originally posted by digital79 View Post
                            Trigger pins are electrically insulated from NO, COM, NC. You also need to provide power source to the bulb
                            Yes which is why I showed you

                            12v -- bulb -- ground

                            This works fine. All I did was add the relay to the circuit. It still has ground.

                            Originally posted by Cerberus View Post
                            If you wire it 12v -- com -- no -- bulb -- ground and then power the relay
                            coil from the 12v direct (no arduino at all) and the bulb doesn't come on...
                            then quite simply the relay is goosed!

                            Or it's some mad relay that needs huge voltage across it's coil.....

                            C
                            Yes this is why I am stumped. This should work! But 4 relays act the same way. I guess I'll try the last 2 to be sure

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                            • #15
                              Originally posted by digital79 View Post
                              what type of relay is it? Any model number?
                              It's the ones the FB folks sell.

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