automatic polarity reversing timer relay?

Discussion in 'The Projects Forum' started by jdthedj10, Apr 19, 2013.

  1. jdthedj10

    Thread Starter New Member

    Apr 19, 2013
    3
    0
    Hi guys,

    I have a project that I am scratching my head on. I want to use a timer relay to run a linear actuator to it's full range out, wait 60 minutes then run it all the way back in, wait for 60 minutes, repeat 24/7. I would even go as far as to say that if it took 60 minutes to reach its full length and then immediately started retracting for 60 minutes I would be fine with that also. I am building an egg incubator and they need to turn several times per day. The guy in this video: http://www.youtube.com/watch?v=YJ4INl1oz1c

    Seems to accomplish this task quite easily and simply. My question is, will this relay do the job I am asking it to? http://www.ebay.com/itm/271083486600...84.m1423.l2649

    or do I need an H Bridge: http://www.ebay.com/itm/1-x-L298N-2A-dual-H-bridge-high-power-DC-motor-driver-board-module-car-/261031568060?pt=LH_DefaultDomain_0&hash=item3cc6b1a2bc
    If so , how would I wire it?
    By the way, everything is 12vdc. I need very laymen explanations please.
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    I'd be inclined to build a large cam wheel, like a crank shaft and a rod, and turn the cam slowly and continuously with a small 12VDC motor and the appropriate gearing. Very simple both mechanically and electrically.
     
  3. jdthedj10

    Thread Starter New Member

    Apr 19, 2013
    3
    0
    Right, ok. That makes sense. Like the motor from a rotisserie oven, But how would I slow it down even more than it runs now? Use something like a dimmer switch?
     
  4. williamj

    Active Member

    Sep 3, 2009
    180
    32
    jdthedj10,

    I would suggest a pulse width modulator (PWM). You can get them completely assembled online for not too much money. Put the output of the PWM in series with the dc motor. Just make sure the modulator is sized appropriately for the motor.
     
  5. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    Your relay has been removed, so I can't see it. But generally you need an H-Bridge to get forward and reverse action. However, you can make a H-Bridge equivilent with two DPST relays. Connect the relays on each side of the motor, and such that in one state, current flows from V+ thru one relay to ground thru the other, then in the other state V+ flows the opposite way, the V+ relay in the first state becomes the ground relay and visa-versa. I have a schematic for this, but it's on my other computer and I have no access to it.
     
  6. jdthedj10

    Thread Starter New Member

    Apr 19, 2013
    3
    0
    PWM is a great addition. I had actually thought of a Rheostat also. Ok here is a pic of the Relay, it seems as though it has a built in dpdt for reversing polarity: [​IMG] and here are thge specs:

    Item:
    Time Delay Relay, Solid-State Timer H3Y-2-60M,12V/24V/110V/220V,1-30M.On-Delay,DPDT,8Pins
    Contact Form :DPDT
    Pins :8
    Dielectric Strength:
    2000V 50/60Hz Min(Not include DC12V) between current-carrying and exposed non-current-carrying metal parts and between contact and control circuit
    Dielectric Strength:
    1500V 50/60Hz Min(Not include DC12V) between control output terminals and operating circuit
    Dielectric Strength:
    1000V 50/60Hz Min between contacts
    Function :On-Delay
    Contact Amp Rating (Resistive) :5
    Coil Volts :12VDC/24VDC/24VAC/110VAC/220VAC
    Rated Time Range: 2-60M.
    Mounting :Surface/Din-Track Mounting(with socket)
    Matched Relay Socket:
    PYF08A, PYF08A-E, PYF08A-N, SYF08A
     
  7. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    DPDT is the correct relay to use for polarity reversal. My mistake.
     
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