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momentary to on/off

Discussion in 'General Electronics Discussion' started by Magoogle, Jul 31, 2012.

  1. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    Hey guys after a lot of Google I finally just decided to type circuit help and found myself here.

    My question is this. On my motorcycle i have a "lap timer" switch on the left hand controls. This switch isn't used for anything at the moment and i would like to use it for turning on and off my radiator fan.

    This is a momentary switch. I would like to know if someone can help me design a simple circuit that will allow this momentary switch to save state and act as a on/off toggle (press for on, press for off)

    12v, at least 15amps

    thanks for any help!
     
  2. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
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    May 8, 2012
    Is either pole of the switch committed to chassis ground?
     
  3. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    switch has 2 wires. as usual with 12v system i would assume one side would of been hot, and one side would of gone to the device its controlling.

    so at the moment they are connected to nothing
     
  4. CocaCola

    CocaCola

    3,635
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    Apr 7, 2012
    There is no such thing "as usual" is this automotive? If it is automotive is there a chassis ground in the general vicinity?

    And we shouldn't "assume" anything if you want to work this out, you should test and verify the way it's hooked up... Identify where each wire from the switch is coming form or going to... Also is the switch carrying the load or is it simply activating a relay down the line that carries the load as is common in 'proper' automotive applications?
     
  5. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    the switch would of told the dash computer to start/stop the lap timer. The switch has 2 wires, once pressed the wires connect, let go the wires are no longer connecting.

    It is on a motorcycle. There would be no relay for this digital control so it should not of been carrying much of a load
     
  6. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    You have said it's two wires, but we need more info, knowing there are two wires means absolutely nothing in the grand scheme...

    Ok we have that established, and now have a point of reference...

    We can't be guessing here, were are these wires coming and going to? What is it driving, is it simply an I/O pin of the computer or some device? Is it high or low logic, what is the polarity of the wires? Earlier in this post you suggested that it would be carrying "at least 15amps" that is quite a bit, now you state it won't be "carrying much of a load" what exactly is this carrying and doing?

    You really need to help us if you want us to help you... If you want a solutions you need to spill the beans and let the information flow, and by that I mean factual information not guesses or assumptions... This includes some testing and leg work by yourself... If you don't have a multimeter this might be a good time to invest in one...
     
  7. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    ok let me try and clear this up alittle bit

    IF the switch was doing its original use, it would of told the computer to start/stop the timer. the wires come out of the hand control and go into the wire harness of the bike via plug which goes to the ecu

    The fan I want to control requires at least 15 amps. I know with how small this switch is there is no way its going to handle 15 amps without using a relay to control the power and the switch to control the relay.

    Obviously I could set this up with any automotive relay and have it turn the fan on as long as the switch is depressed. However i want to be able to press and release to tell the relay or circuit we design to turn on, then press and release again for off.

    Yes i have a multimeter, I ohmed the switch between each of the 2 wires and with the multi set at 2k i got .922 if that helps at all.

    What other information can i provide to help?
     
  8. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    So basically you want to totally remove the wires going to the switch as they will no longer be used, and repurpose the switch to turn on and off a fan?

    Take you multimeter set it to a volt setting in excess of 12 volts and touch the black lead to the negative battery terminal and the red lead to each of the wires going to the switch...

    Post results...
     
  9. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    ok the 2 wires (red/white strip and brown) Brown has 12.5v going to it, and red/w is dead until switch is depressed
     
  10. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
  11. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Now that we have some relevant info, we can work something up... We now know we have a supply at the switch so that helps, bikes should be chassis grounded so that helps... No we just need to make a one shot that latches a relay, I will try to get to it later if no one else does, I have a few things to do tonight so time is short...
     
  12. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    thanks, i appreciate the help! im going to have to wire it up temporarily for push and hold operation on a 15amp automotive relay until we can figure this out. Let me know what you come up with :)
     
  13. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    A brief stop by, if you want to go at it yourself we can certainly do that, but here is a damn quick and easy over the counter option for a very reasonable price...

    http://www.pololu.com/catalog/product/750
     
  14. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    wow that is awesome, it says 10 amps though.. im not sure if that will handle the fan because the fan originally had a 15amp fuse so what are your thoughts?
     
  15. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Yeah, don't drive the fan directly, drive a properly rated relay with that module that will drive the fan...
     
  16. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    ha oh duh, man thanks alot that didnt even occur to me. I will go with this option hopefully it wont take long to ship
     
  17. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    I have used that company in the past for laser cutting and they had good turn times...
     
  18. Magoogle

    Magoogle

    62
    1
    Jul 31, 2012
    bought 2, and ordered via overnight shipping shall see how long it takes. I know where to go if i have more circuit questions :)
     
  19. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
    648
    May 8, 2012
    The board may include it but if it doesn't you'd be well advised to put a reversed biased Diode across the relay coil.
     
  20. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Good catch, I'm usually the one chiming in and reminding people of the flyback diode, just a little distracted last night and totally missed it......
     
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