Can someone show me how to set up an 8 pin relay?

Discussion in 'The Projects Forum' started by Gibling, Jun 12, 2009.

  1. Gibling

    Thread Starter Member

    May 28, 2009
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    Ok so I'm a complete noob at relays, and well, circuits too. So would someone be able to expain in the most uncomplicated, simple minded way possible how to set up an 8 pin octal relay. This one to be exact.

    Basically, I have a DC power source, and a DC motor. All I want is for the motor to turn one direction, then when the relay time is up, for the current to reverse and the motor to turn in the other direction. As it's a repeating relay, I want this to continue until I turn it off.

    Would someone be able to draw up which wires go where on the actual 8 pin socket? Or if there's anything I need to add for this to work could you draw that too?

    Thanks for your help!
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    You need the relay socket that is pictured on the page that comes up. The relay will not work without it.

    You can go to the manufacturer's site and get the drawing for the relay, or just wait until it arrives - there is a pin diagram on the case.

    The NC contacts are closed when the relay is unpowered, the NO contacts close when the relay is powered. To reverse the motor, you reverse the voltage to it.

    Your motor may overheat and die from this treatment. It is best to let the motor stop rotating befre reversing it.
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Electrically, the attached is how you could hook it up. But, like beenthere said this is hard in a motor. Reversing a running motor puts a lot of stress on it mechanically and electrically.

    ken
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Something like this? Do you have limit switches to prevent a clashing of gears when relay says GO and mechanical limits says STOP?
     
  5. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Bernard,

    The pin you labeled "7" on the common terminal on the lower set of contacts should be "8".

    Ken
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Just for reference, the original thread is here: http://forum.allaboutcircuits.com/showthread.php?t=24025

    Gibling, you need more than a simple timed relay for your application.

    You must have limit switches to detect when the container is at the limits of it's travels.
    You can use Hall-effect sensors, but they can fail. A normally-closed switch that breaks the circuit when activated would provide a degree of safety to prevent damage when failure occurs.

    You must keep in mind that everything will eventually break/wear out/fail, and to build things so that when failures occur, nothing bad will happen.

    It will prove impossible to simply set a time on a relay, and have the barrel rotate horizontally/vertically to arrive in the exact same position every time.

    The best use for the timer relay would be to provide a "coast-down" delay for the motor when a limit is reached.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    And the pin labeled "2" on the common terminal on the upper set of contacts should be "1".
     
  8. Gibling

    Thread Starter Member

    May 28, 2009
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    Ok thanks guys. I'll mention all the technical/safety details to my boss, and hopefully he'll take them into consideration and/or get a professional to build what we need. This has turned out to be much more complicated that I imagined. Mad props to y'alls!
     
  9. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    A little late, but thanks Sgt. & Ken for covering my 6. Should have had my coffee first.
     
  10. Kauhu

    Member

    Mar 7, 2009
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    Indeed, you must stop the motor before reversing it. Otherwise it will burn. Shame I don't have old school assignments saved anymore, I did this same thing with couple timed relays. It also had a safety switch so that the direction couldn't reverse if the motor was running.
     
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