Using relays.

Discussion in 'The Projects Forum' started by adam_fozz, Jan 19, 2012.

  1. adam_fozz

    Thread Starter New Member

    Jan 19, 2012
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    Hi all,

    I'm building an electronic coop door opener for my chicken coop and have hit my electronics limit! I have a wifi camera in my coop which has a relay output fr an alarm which can be activated by a computer or phone. It had the volt meter on it and when switched on it simply created a circuit. Now I want to use this to trigger a drill so as I see it I have two issues.

    1. The drill we need a 12v supply so I will need to just is the 5 volt relay to
    Activate the 12v circuit somehow??

    2. How can I use one relay to switch between driving the drill one way and the other so that i can both open and close the door?

    Any help will be great. I know the basics but I have never used relays.
    Adam_Fozz
     
  2. crutschow

    Expert

    Mar 14, 2008
    12,991
    3,227
    If the contact current rating of the relay is greater than the current the drill requires, then you can just connect the relay contacts to control the drill. Do you know both those values (relay contact rating and required motor current)?

    How do you trigger the drill?
     
  3. adam_fozz

    Thread Starter New Member

    Jan 19, 2012
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    0
    All I know about the relay is that it can output either 5v or no current. Whichever way you prefer. This led me to believe that the circuit wouldn't handle the 12 volts of a cordless drill.

    I was planning on wiring up the switch so that the drill would power in when the relay activates and makes the circuit. But my
    Second questions was how I could reverse this so that I could make the drill go the other way. Any ideas?

    Adam
     
  4. Brownout

    Well-Known Member

    Jan 10, 2012
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    998
    Is the drill reversible? If so, just figure out which set of wires turn it one direction, and which turn it the other direction. Then, active the set of wires for the direction you want to do.
     
  5. adam_fozz

    Thread Starter New Member

    Jan 19, 2012
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    Thanks Brownout. I know how to get the drill to work in the circuit, my question is how could I make one switch swap it from going one way, to the other. So, for example, I could flick the switch and it would make the door close then when its closed the next time I flick the switch it makes it winds the other way so that it opens. Does that make sense?

    What about the other issue of using a 5v relay circuit to activate a higher voltage circuit? Any advice?

    Adam
     
  6. Adjuster

    Well-Known Member

    Dec 26, 2010
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    Given what you have said so far, your camera's output may itself be from a relay, or it may be a signal designed to drive a relay. There is a difference - this may become clearer to you by carefully looking through the maker's instructions for it.

    Otherwise, posting details of the model number and any instruction details may help others on the forum to advise you.

    Without further information, it might be wisest to assume that the camera output was very light duty, and so only capable of driving a heavier power relay through an amplifying device such as a logic-level MOSFET.
     
  7. adam_fozz

    Thread Starter New Member

    Jan 19, 2012
    7
    0
    Hi, Thanks,

    The camera itself does have a relay in it. I know this because when use my phone to turn the switch the function on I hear tell tail sound of the relay switching.

    The manual only says that you can either make the relay output 5V or switch to its NO circuit. I have asked the manufacturer to let me know the maximum current and voltage that this relay can take and I will report back.

    But removing that from the equation, do you have any idea about electronic items I could use to switch between the clockwise circuit on the drill to the counterclockwise? I just tried to draw something up using reed switches and magnets but this wont work because they would only make a connection when the door is either fully open or fully closed. Essentially I need a way to automatically choose the correct circuit to activate based on if the door is already open or already closed. Any Ideas?

    Adam
     
  8. williamj

    Active Member

    Sep 3, 2009
    180
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    adom_fozz,

    If I'm reading your posts right you are going to need a solid state control circuit. Say you want the door open for 12 hours a day and then closed for the remaining 12 hours, which ever way it's connected, the relay will have to be energized for 12 hours at a time. And that will result in premature failure of the relay.

    What you will need is a circuit that when you pulse (energize and then immediately de-energize) the relay the door will open and then the next time you pulse the relay the door will close. And that requires a solid state (either discrete or IC components) circuitry.

    williamj
     
  9. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,772
    931
    With it being a mechanical system, more choices are open to you.

    A single switch with a 'fancy' handle could do this.

    Just imagine a small object shaped like a soda straw, with a stop or tab on either end. The switch (slide type) will be moved up or down by the 'soda straw' depending on whether the mating tab on the door contacts its upper end or contacts its lower end.
    In effect this just extends the end limits of your switch to the entire length of the door. Push its extended pole up when the door is fully raised and the switch places the motor wires in the position to drive it down when next powered on, etc. etc. etc.

    Do you understand what I'm trying to picture for you?

    You would need to use a DPDT switch.
     
    Last edited: Jan 20, 2012
  10. adam_fozz

    Thread Starter New Member

    Jan 19, 2012
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    This sounds promising Williamj. Can you elaborate on what sort of components I could use to achieve something like this?
     
  11. Brownout

    Well-Known Member

    Jan 10, 2012
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    If your drill is reversable, then you can use this drawing as a guide. The switches in the drawing represent the realys needed. One relay makes the door move, and the other determines which direction.

    As for 5V, 12V operation, just find relays with 5V coils and 12V contacts. I would not try connecting 12V to a relay rated for 5V.
     
  12. williamj

    Active Member

    Sep 3, 2009
    180
    32
    adam_fozz,

    I wish I could elaborate but solid state is really not my strong suit. My strengths lay in motor controls using relay logic (really old school now_a_days). I do know that there are circuits (IC and descrete) that do precisely what you want. I've been hanging around here at AAC for some little time now and I know the good people here are knowledgeable and are willing to help but you need to lay everything out for them so that assumptions are kept at a minmum.

    And I assume what you want is, if I'm not mistaken, to control the door using the relay inside the camera from where the camera monitor is located. That being said I'm assuming that power is already at the coop and you have no desire to pull more wires from the monitor to the coop.

    These are just a couple of things that we need to know are fact and not assumptions. If Ican be of help I'll be more than happy to but I'll leave things that are not in my strong suits to those who are more knowledgeable.

    williamj
     
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