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12 volt door latch wiring

Discussion in 'Sensors and Actuators' started by christopherF, Jul 29, 2018.

  1. christopherF

    christopherF

    3
    0
    Jul 29, 2018
    Hi,
    New to the forum. I would like to make a self feeder for my horses. It would be a box with a hinged side door that would drop open and leave a hay bag exposed for a one time feeding. I want to put a solenoid door latch to keep door closed and then drop open at a pre-set time.

    For now, a 12 hour timer would be sufficient. I need 4 of these feeders. Questions- Would the 12 volt solenoid door latches I see online for about $6-$12 work? I don't know if they would open for a split second with power from a battery and then close so no power was consumed. I was thinking of using just a wind up 12 hour timer but not sure how it would energize the latch then break the circuit so latch is not held open using up battery. I envision the latch, timer and small battery mounted on each individual feeder that can be used outside in good weather and moved inside when wet.

    Horses are fed twice a day and it is difficult to always find someone to feed just once if we decide to stay out later than usual feed time.
     
  2. Bluejets

    Bluejets

    2,981
    578
    Oct 5, 2014
    As I see it, a spring loaded or gravity operated door or cover could be "trip" operated by a basic solenoid but how do you close it again or is this not necessary?
    Perhaps all the feed is gone so no need?
    If closing is necessary, then a windscreen wiper motor/gearbox would be one alternative.
    Battery driven (car battery) which would also drive any timer/relay module and limit switch arrangement.
    Don't know about your choice of solenoid but if you have some basic design ideas and some detail of the solenoid then that would be a good start to getting some further help.
    Battery power being present, no need for wind up timers. Plenty of economical electronic alternatives are available.
     
  3. christopherF

    christopherF

    3
    0
    Jul 29, 2018
    2018 12 volt latch.jpg this type of latch. No the door does not have to be reset. For now, this is a one time feeder only. Door opens, hay bag is exposed, horse eats, we dont have to be home at 6pm to feed
     
  4. Bluejets

    Bluejets

    2,981
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    Oct 5, 2014
    With your choice of latch, it would depend on how you intend to rig up the rest of the mechanism and how much "load" there would be on the latch.
    The one shown has around 12w of power ( 12v x 1A) which is not a lot really.
    Latch has only so much pulling power and under normal use ( door latch) there would be next to zero load.
    i.e.latch operates the armature ( connected to the wedge bit) allowing door to open.

    There are ways to make your latch operate at a mechanical advantage but beyond the scope of discussion here I believe.
    Think along the lines of how the old mouse traps used to work.
     
  5. kellys_eye

    kellys_eye

    4,289
    1,143
    Jun 25, 2010
    Think along the lines of a DOOR catch - the type that (if you look closely) has one edge flat and the other 'curved' (to allow the door catch to close).

    Add a solenoid to a catch of this type and, using a ONE-SHOT (monostable) circuit, the solenoid will pull for the 'period of the one-shot' and allow the door to drop open.

    You may need a small spring behind the door to give the door a push and help it drop but that depends on how you make it.

    A simple timer (plug-in if you have access to mains supplies at the feeding place?) powering a mains-powered one-shot timer (can be bought as ready-made module) is the easy way.

    If you are limited to battery power you could purchase a monostable/timer that operates from 12V from many eBay suppliers (inevitably located in China) to achieve the same result.
     
  6. christopherF

    christopherF

    3
    0
    Jul 29, 2018
    9E2EDB7F-A3DA-4F0B-8920-27F56231AB1D.png I would prefer it to be 12 volt to be portable.This is a more heavy duty latch/solenoid than first one. I cannot find a 12 volt one-shot monostable/timer that is self contained (timer,dial or readout, and mountable with two wires sticking out to connect to latch) Will I have to “build” the timer circuit? I’m a farmer, but not experienced with building circuit boards.
     
  7. Bluejets

    Bluejets

    2,981
    578
    Oct 5, 2014
    Ebay.... See if I can link you to one.
    What is the readout for?
     
  8. Bluejets

    Bluejets

    2,981
    578
    Oct 5, 2014
    Multi-purpose unit here.....this is an Aus site but should be available anywhere in Ebay.

    https://www.ebay.com.au/itm/Digital-LED-Infinite-Cycle-Loop-Delay-Timing-Switch-ON-OFF-Relay-Timer-Module/112439920682?hash=item1a2df1082a:m:mi4wzCdMQFz8atu5Pq5ywUQ&var=412830497925&_sacat=0&_nkw=+timer+module&_from=R40&rt=nc&_trksid=p2334524.m570.l1313.TR2.TRC0.A0.H0.X+timer+module.TRS0&LH_TitleDesc=0|0

    Scroll down the page and see connections.....your application would be as in the third photo.
    (module control DC load diagram 2)

    Don't be concerned about the trigger switch shown as it will not be used in yours.
    (maybe...maybe not...see last note)

    Programming...well, you may have to round up one of the kids.
    (4 years and older usually works for me)o_Oo_O

    Can be a little confusing at first BUT yours should be P4 under Function introduction

    I would be inclined to add a power switch or simply disconnect the power when not used.

    Then down to Use Operating Instructions where you will need to follow through to step 8.

    Note:- Looking at the unit further I think maybe settings are lost when powered down so may have to look at the "trigger" option instead.

    When ordering remember to select the 12v dc version.
     
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