Relay Board Problem

Discussion in 'The Projects Forum' started by Kiks, Jan 6, 2011.

  1. Kiks

    Thread Starter New Member

    Jan 6, 2011
    9
    0
    Hi I'm Newbee here. :)
    I already done this project (Quiz Show Buzzer).
    But there a problem with the project, all 8 light bulbs [220 VAC] were lit after pressing the button/s. Thus problem happens around 6/10 occurrence during exercise.
    Ideally only one output should be lit [the first one] after pressing all 8 push buttons simultaneously.
    There are snubbers on the coils of the relay.
    Light bulb are needed for quizzer's indicator which indicates that he was the first pressed the button.

    Observations:
    [1] Operation is OK if (a) relay board [enclosed with red] is not included; and if (b) relay board is included but no 220 V AC supply connected.
    [2] Operation is not OK if connect the 220 V AC supply.

    Question:
    [1] What the possible cause of this problem?
    [2] What solutions to eliminate the problem?


    [​IMG]
    Circuit file:
    http://www.4shared.com/file/9iR5x57o/quizbuzzer_rev6.html

    Download:
    CircuitMaker 2000. The Virtual Electronics Lab
    <SNIP>

    TIA.
    Regards to all. :)
     
    Last edited by a moderator: Jan 6, 2011
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,795
    951
    It is possible the current draw is large enough(cold incandescent) that a 'supplementary' magnetic field is added to the relay coil from the surge, activating the relay.

    Try a different larger relay designed to switch larger AC loads or designed for start surges to see if the problem is solved. one or two switched around between different channels for testing should let you know if it is relay related.
     
    Kiks likes this.
  3. Kiks

    Thread Starter New Member

    Jan 6, 2011
    9
    0
    Thanks. :)

    I'm planning to replace the relay board with SSR or use 12V DC light bulb eliminate the electrical noise which impacted to digital crcuits.
     
  4. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    your relay board is opto isolated, and if reasonably designed, will not impact the signal quality. This means AC one end, isolated DC on the other with physical seperation.

    what is the source being used to operate the coils and what are the ratings of the relays?
     
  5. Kiks

    Thread Starter New Member

    Jan 6, 2011
    9
    0
    103 or 10nF or 0.1uF were placed on 5VDC & 8VDC power supply output and on each digital IC but problem is still exist.



    Relay has 6VDC for relay's coil and 110V for relay's contacts.
    I'd applied 8VDC to relay's coils because 6VDC will drop down during full load.
    I'd used the 220VAC for relay's contacts since it passed during component evaluation.
     
  6. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    I would try sinking the bases of your relay drivers. I can't see the schematic clearly enough to recommend a resistor value, but a 1K should be Ok. Try it on one driver and see if it makes a difference. Failing that, I suggest you post an image of your relay board, both sides, so we can see your technique.
     
    Kiks likes this.
  7. Kiks

    Thread Starter New Member

    Jan 6, 2011
    9
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    [​IMG]

    click on the image then download.
    Open as jpeg.

    Thanks. Really appreciate your help.
     
  8. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    personally, I'd change the base source resistors to 1 or 2k, and sink the bases with a 10k. Try that on a single opto/driver and see if it breaks away from the fault.
     
  9. Kiks

    Thread Starter New Member

    Jan 6, 2011
    9
    0
    During bread board prototype, originally this is 1KΩ but the problem is the collector voltage is enough to energize the relay even in logic 0 on TTL outputs. I'd tried several resistor with higher value until 10KΩ is fitted in design.
     
  10. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    Could the push-button wiring be picking up interference, possibly radiated from the relay board / lighting wiring? I don't suppose that it would be practical to screen the wiring, but you might try adding small capacitors (say 10nF) from each of the latch inputs to 0V.
     
  11. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    you could disconnect the DC signal inputs and drive the inputs individually to test the input side. What specific transistors are you using.
     
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  12. Kiks

    Thread Starter New Member

    Jan 6, 2011
    9
    0
    you could disconnect the DC signal inputs and drive the inputs individually to test the input side.
    -works fine. problem didn't occured

    What specific transistors are you using.
    -C9013/TO-92

    Could the push-button wiring be picking up interference, possibly radiated from the relay board / lighting wiring?
    -yes, possibly because of RFI

    I don't suppose that it would be practical to screen the wiring, but you might try adding small capacitors (say 10nF) from each of the latch inputs to 0V.
    -done, problem still exist.



    Solution:
    relay board will replace with electronic solid state relay circuit.
    [​IMG]
     
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