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how to reverse the polarity of a DC motor using a DPDT relay, limit switch, and timer?

Ok, i am not an electrician and understand very little, but here's what i want to do.  I have a reversable 18V cordless drill I have taken apart to get at just the motor.  What I want it to do is turn on automaticallly with a timer in one direction and shut off (with a limit switch?) after about 2 seconds.  About 14 hours later I need the opposite action. Both actions automatic using a timer with AC power.  The application is a door opening and closing veritcally (chicken coop door).

rickharris1 year ago
Your looking for a H bridge configuration as Steve has drawn for you - Lots here from a search.


http://www.instructables.com/pages/search/search.jsp?cx=partner-pub-1783560022203827%3Anpr2q7v5m6t&cof=FORID%3A11&ie=ISO-8859-1&q=H+bridge
StevesBees (author)  rickharris1 year ago
Hi Rick, can i use a 12V timer if i have an 18V motor? i can't find a timer that will turn on/off in seconds. best i can find is 1 minute intervals. will that still work?
I designed this for another 'ibler a few months ago, for his chicken shed too.

You need to find a suitable timer.

The first circuti is made up of parts from Radio Shack, the second kind of shows the circuit your making. Check the pin out of the relays carefully.
Hen door relays.jpgmotorrelay.jpg
PS Consider TWO down switches on the down action, one on the actual door mech, the other on the door edge, so you don't dice your livestock.
PPS The last one we also put a photosensor on, rather than a timer.

Steve
StevesBees (author)  steveastrouk1 year ago
Hey Steve, thanks for the info. few more questions, as stupid as they may be... can i use a 12V timer if the motor is an 18V motor with a 25V charger? also the timer can only do 1 minute intervals like an irrigation timer. is this still ok with this circuit? i was thinking something like this:
http://www.ebay.ca/itm/DC-12V-Digital-LCD-Power-Programmable-Timer-Time-switch-Relay-16A-/290638467872?pt=LH_DefaultDomain_0&hash=item43ab671320

thanks again, steve
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