Troubleshooting DPDT Relay in my speaker switch project

Discussion in 'The Projects Forum' started by peaboy, Dec 28, 2012.

  1. peaboy

    Thread Starter New Member

    Dec 28, 2012
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    I'm using a pair of DPDT Relays and a SPDT on/off/on switch to make a speaker switch for the car stereo on my boat so that I get 8 Ohms when in parallel and then it removes one set of speakers so I get 4 Ohm. My deck can handle this.

    When I wire it up, the switch has no effect. All of the speakers stay on all the time with the switch in any position. I can see the relay close and the indicator on the relay lights up when I use the switch.

    When I remove the switch from the circuit and manually jump a relay the speakers on that relay are disconnected as expected.

    Here's a schematic
    [​IMG]

    Any ideas as to why this is behaving like this?

    Thanks,
    -p
     
    Last edited: Dec 28, 2012
  2. tubeguy

    Well-Known Member

    Nov 3, 2012
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    If you follow your schematic, there is (always) a connection thru the speakers back to the amp outputs.

    2 8-ohm speakers in parallel are 4 ohms, so 1 set would be 8 ohms, 2 sets in parallel would be 4 ohms.

    With the SPDT center-off switch you could design the circuit to select 1 pair, both or other pair.
     
    Last edited: Dec 28, 2012
  3. tubeguy

    Well-Known Member

    Nov 3, 2012
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    One more important thing.
    Car stereo amps sometimes don't have the - speaker outputs connected to ground or together because they are operated in bridge mode
    So, do not connect the left and right speaker negatives to ground or together or damage could result.
     
  4. peaboy

    Thread Starter New Member

    Dec 28, 2012
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    That is what I thought I had done.... can you point me in the right direction?

    Thanks,
    -p
     
  5. tubeguy

    Well-Known Member

    Nov 3, 2012
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    Relay coil wiring looks OK.
    Hints:
    Remove all wiring between speakers and relays.

    You have the right start on the top relay.

    Change amp connections:

    Left + to both Relay C1 contacts
    Right + to both Relay C2 contacts

    Left - to both Left spkr - only
    Right - to both Right spkr - only

    What would the final connections be. Please post schematic BEFORE testing..;)
     
  6. peaboy

    Thread Starter New Member

    Dec 28, 2012
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    Thanks for the help and for walking me how to think about it.

    This is my first crack at this, but I think it might be wrong.
    [​IMG]

    The way I drew it the speakers are NOT connected at all when the switch is in the OFF position. I am thinking OFF should be ALL Speakers. So The speaker +'s should be wired to posts of the relay which are connected when the relay is off. So they would be connected to the terminals marked 9 and 12 instead of 5 and 8. Like this...

    [​IMG]

    Is the second drawing correct?

    Thanks a lot.
     
  7. peaboy

    Thread Starter New Member

    Dec 28, 2012
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    Just saw another issue as i was sleeping. I have the + speaker wires wrong. Each room goes to one relay.
     
  8. tubeguy

    Well-Known Member

    Nov 3, 2012
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    The second drawing is partially correct in that you have all the speakers on when the switch is centered.

    Yes ...sleeping on it helped ;) (always works for me !!!)

    Swap the + connections so you have the top pair on the top relay, other pair on the bottom.
     
  9. peaboy

    Thread Starter New Member

    Dec 28, 2012
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    Thanks a lot for you help. Here's the final drawing for any else who needs to do this.

    [​IMG]
     
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