Time delayed relay board

Discussion in 'The Projects Forum' started by JonL, Aug 9, 2012.

  1. JonL

    Thread Starter New Member

    Aug 9, 2012
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    Hello,

    I'm working on a small project, and I need to switch on an USB hub after a small ammount of time (60s, maybe 90s).

    I bought this relay board: http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=150868252143&ssPageName=ADME:X:RTQ:GB:1123


    So, I've connected Vcc and GND, and I got the red LED lit up. Problem is, the timed delay never triggers, and I never get the green LED lit up.

    Also turned the timer knob, but got no luck.

    So, as anyone used this kind of board? Do I have to connect anything else?

    Complete noob here...
     
  2. wayneh

    Expert

    Sep 9, 2010
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    It's tough to tell since I can't read chinese, but I think you need an external trigger signal, not just power applied.
     
  3. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    My guess is that the two header pins on the same end of the pcb as the power connections have to be shorted together to start the timer. The pot is to adjust the delay time.
     
  4. JonL

    Thread Starter New Member

    Aug 9, 2012
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    Well, there's an IN label there next to the GND pin, but no pin.
     
  5. JonL

    Thread Starter New Member

    Aug 9, 2012
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    Thanks, I'll try shorting those pins.
     
  6. JonL

    Thread Starter New Member

    Aug 9, 2012
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    Shorting those pins made the green LED lit. :D

    Now, the problem's that the timer delay never ends. I tried the pot turned all the way clockwise and all the way anti-clockwise, but it never triggers... oh well...

    Any more suggestions? Or does anyone know a relay board of this kind that is known to work well?
     
  7. BSomer

    Member

    Dec 28, 2011
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    Once you shorted them did you remove the short? It is probably a trigger input that just requires a pulse (on/off) not a constant on.
     
  8. JonL

    Thread Starter New Member

    Aug 9, 2012
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    I tried removing the short now and that worked.

    So, that means that I'll have to apply a 5V pulse to those two pins in order to make the trigger work?
     
  9. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I don't think so. Looking at the PCB, it appears that there is a wire link from the GND input pin to one of the two trigger pins. If so, then a normally open switch would be connected across those pins. When the NO switch is closed, the GND would be connected throught the switch to the other pin, and when the switch is released, the timer would start.

    The switch could be any small NO switch, e.g., pushbutton or relay contacts that were controlled by a light sensor, a PIR sensor, or numerous other possiblities.
     
  10. JonL

    Thread Starter New Member

    Aug 9, 2012
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    I see...

    So, I guess I must find some other board that guest triggered with a constant on, not a pulse.

    Anybody know of one?
     
  11. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    If you describe exactly what you are trying to accomplish, someone here will be able to help. Maybe the board that you have can be made to work. Just explain your objectives.
     
  12. JonL

    Thread Starter New Member

    Aug 9, 2012
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    I'm using this motherboard http://www.pcengines.ch/alix1d.htm, and I need to insure that a USB hub is powered some seconds after the board boots, because sometimes some USB gadgets aren't recognized correctly by the operating system (linux).

    So, I intend to use that relay board for that. I'm feeding Vcc and GND from the GPIO pins.

    Don't know if I can get some trigger signal off the motherboard.
     
  13. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Okay, you want to be sure that the MB has booted before the USB hub is turned on, but you want it to be turned on just after the MB has booted. And you want the hub to stay on until the computer is shut down? Is that correct?

    I have never used GPIO pins. Are you powering the relay board directly with 5 VDC from the GPIO? And if so, is the turn-on timing what you are seeking?

    And bear in mind that I have never seen the relay board and am only guessing how it works.
     
  14. JonL

    Thread Starter New Member

    Aug 9, 2012
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    Yes, that's correct.

    Yes and yes.

    Sure, any help is appreciated. Thank you.
     
  15. tracecom

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    Apr 16, 2010
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    In that case, it seems that all you really need is a relay that has a 5V coil and a set of contacts to control the mains power to the wall wart that powers the USB hub. The 5V from the GPIO pins would energize the relay, which would switch on the wall wart, which would stay on until the PC is powered off. If that is correct, then you can permanently short the two pins on the relay board, and the relay should operate as soon as the relay board is powered up. Then, with the power to the wall wart run through the NO contacts on the relay, you would accomplish what you want. Or am I missing something?

    Oh, and if that would work, it would probably be safer to run the DC out of the wall wart through the relay.
     
  16. JonL

    Thread Starter New Member

    Aug 9, 2012
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    Sorry, you got me lost there. Remember, I'm a noob. :D

    So, you advise me to use a different type of relay?
     
  17. tracecom

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    No, I am suggesting that the board you have now might work. If you permanently short the two pins on the relay board, the relay should operate as soon as the relay board is powered up by the GPIO pins. Then, with the power out of the wall wart run through the NO contacts on the relay, you would accomplish what you want.
     
  18. JonL

    Thread Starter New Member

    Aug 9, 2012
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    I see. I've tried it and that doesn't work.

    If I short the two pins, the green LED lits up, but only when I remove the jumper (as suggested by BSomer) the delay timer starts.


    I guess I need something that sends a pulse to those pins when voltage is applied.
     
  19. JonL

    Thread Starter New Member

    Aug 9, 2012
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    Yes, I guess that's it.

    I have a motherboard test kit that has a power switch to connect to motherboard headers.

    I tried the switch on those pins an it worked.

    So I need something that could send a pulse to those pins when voltage is applied. Question is: what? :D
     
  20. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    You can do that with a 555 monostable multivibrator circuit, but before I tried that, I would look to see if I could just bypass the timer circuitry on the relay board and power the relay directly with the 5V from the GPIO.
     
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