Chicken coop door circuitry with lamp timers

Discussion in 'The Projects Forum' started by jmh226, Nov 9, 2015.

  1. jmh226

    Thread Starter New Member

    Nov 7, 2015
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    Hi all!
    I have decent mechanical abilities, and decent electrical abilities as far as house wiring, but have not done a tremendous amount with component circuitry.

    I am trying to build an automatic chicken coop door opener, that raises a door vertically by using a small DC gear motor to wind a thread around a shaft.

    I have two DC transformers (wall warts) that are plugged into two basic lamp timers. In the morning the "up" timer will turn on and the motor will raise the door until a NC magnetic switch is tripped at the top of the run (magnet on the door, switch affixed to the door frame). The timer turns off after about 15 minutes, so the relays and circuitry aren't sucking up power all day. In the evening the other timer turns on activating the DPDT relay coil and switching the polarity of the motor so that the motor closes the door again until the magnetic switch is activated.

    Does this look good as far as the circuitry goes? Am I missing anything?

    On more of a curiosity note, my first attempt was largely the same but had no DPDT relay, just two sets of leads attached to the motor, each from a timer/wall wart with only one set active at a time. It didn't work...any idea why? Presumably some circuitry inside of the non-energized wall wart was still active despite not being switched on by its timer?

    Thanks everyone!
     
  2. MikeML

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    Oct 2, 2009
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    Are you sure the motor reverses if the polarity of an applied DC voltage is reversed?

    The easiest way of doing this is with a DPDT relay. You can do it with two SPDT relays...
     
  3. jmh226

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    Nov 7, 2015
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    Yes - I checked that :)
     
  4. jmh226

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    Nov 7, 2015
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    Are you able to see the pdf circuit diagram that I included? I did use a dpdt relay.
     
  5. MikeML

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    Here is how I would do it:

    The relay coil is controlled directly by the timer output. This presumes the timer is programmable such that you can pull-in the relay at 6:00am?, and drop it out at 5:00pm?
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Another method of reversing the motor with minimum components and wiring is to wire both N.C. end limit switches in series with the motor, wire a reverse biased rectifier across each switch, so that when the switch opens it is forward biased for the reverse polarity.
    All you need to do then is reverse the DC to the motor circuit.
    Max.
     
  7. MikeML

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    Does that assume you are supplying the motor and circuitry with AC?
     
  8. jmh226

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    Nov 7, 2015
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    This makes sense to me as another way to accomplish the same thing, but is there an advantage to it over the way I currently have it laid out?
     
  9. MikeML

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    One relay versus three, one power supply vs two...

    The timer can put out 120AC if you use a relay with a 120Vac coil; use a DC supply for the motor...
     
  10. jmh226

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    Nov 7, 2015
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    Unfortunately this is over my head :( What does a reverse biased rectifier do? Or maybe this is too basic a concept for explanations here?
     
  11. jmh226

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    Nov 7, 2015
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    The two spdt relays only function to protect the magnetic switches from being overloaded and failing when the load going to the motor passes through them. (This happened the first time I wired it up with no spdt relays) And I still need two power supplies don't I? One to turn the motor on (a timer that is on from 6am-6;15am, and then again from 7pm - 7:15pm) and one to switch the polarity (on from 6:45pm-7:30pm to ensure that the polarity is reversed for the second time the motor is on) Or am I missing something?
     
  12. MaxHeadRoom

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    As the devices, sw's, motor, are all in series if a switch opens, it disables the ability to run in the reverse direction, wiring a diode (rectifier) across each of the switches, will not allow the motor to run in the direction that the limit has opened in, but allows it to run when you reverse the polarity to the motor.
    I could sketch it up if interested.
    Max.
     
  13. jmh226

    Thread Starter New Member

    Nov 7, 2015
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    If you're up for it, I'd be interested in seeing this method drawn out for the academic purpose, though realistically since I already have all of the relays and components for my original sketch, I'll probably use that method :) Does it look like my original sketch will work as designed?
     
  14. jmh226

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    In looking up info about relays, it seems like it is common to wire a diode in parallel with the coil. Is this something that I would need to do in my circuit? If so what size/kind of diode?
     
  15. MaxHeadRoom

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    A 1n4007 would be OK, for the coils.
    Polarity is important.
    Max.
     
  16. #12

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    That is used in DC circuits. Just in case you had some confusion going...
     
  17. dl324

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    Mar 30, 2015
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    It's difficult to follow your sketch because you haven't labeled the function of RY1/2 and S1/2. You also have some unnecessary wire bends and aren't following the convention of having the flow be left-to-right and top-to-bottom.

    As already mentioned, you only need the DPDT relay; plus your two timers and limit switches. It isn't clear if S1/2 are the lamp timers used to turn the wall warts on and off or the limit switches.
     
    Last edited: Nov 9, 2015
  18. MikeML

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    Since you are using magnetic door sensors as limit switches, and they are not up to switching the motor current directly, then you will have to add the two extra relays to isolate the sensors from the motor current . The relay contacts should be wired such that the contacts are closed while the door is in transit, and one or the other opens when the door reaches the upper or lower limit.

    You only need one timer if it is the kind that turns on a 120Vac lamp at one time (say 8pm), and turns it off at another time (say 6am).

    [​IMG]

    In that case, the DPDT relay that reverses the motor will need a 120Vac coil, and will stay energized all day. The relay coil will draw a couple of W, less than your second timer.

    You only need one DC power supply if you use the DPDT relay to reverse the polarity to the motor.
     
  19. jmh226

    Thread Starter New Member

    Nov 7, 2015
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    Sorry about flouting conventions, this is the first circuit diagram I've ever drawn, so my next one will be better! s1 and s2 are the limit switches (magnetic switches like the type used in security systems), the voltage sources are the wall wart/lamp timers (I guess the timers should really be switches too!) r1 and r2 are only there to prevent the full motor load from passing through the magnetic limit switches. They serve the same function as the limit switches, but at a higher amperage.
     
  20. jmh226

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    Nov 7, 2015
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    How do I do this with one timer? If the timer turns on at 6am and this energizes both the DC wall wart and the dpdt coil, how does the polarity ever reverse...or is the dc power source just plugged into the wall, with only the coil on the timer? What is the power draw of the wall wart being plugged in all day vs the extra lamp timer? Which will be more efficient? How do I measure this?
     
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