Instructables

How can i get a 12v motor to automatically reverse polarity or direction by a adjustable timer ???

I have a machine that i built for hunting that swims  duckdecoys back an forth that mimics a live group of ducks and would like to control it by an adjustable timer to automatically reverse the direction of the motor  instead of having to hit a switch back an forth.Heres what i need exactly a timer that is adjustable by a knob that will switch direction of motor after a certain time an adjustable speed control by knob for the motor to speed up an slow down the motor an a on/off switch to turn the system on an off if someone could help me with a parts list and a schematic of how it all goes im shure i can figure it out

A better method is to use a couple of limit switches, so they run from one end to the other, hit a switch, reverse and go back, where they hit a switch, and come back again.

Steve
frankswamper (author)  steveastrouk2 years ago
How would i hook them up to run after switch is hit an only other problem is water proofing the switches unlick the timer i can have out of water the switches would have to be in the wayer by the pulley
Several solutions here

https://www.google.co.uk/search?num=10&hl=en&safe=off&site=imghp&tbm=isch&source=hp&biw=1902&bih=882&q=motor+reversing+limit+switches&oq=motor+reversing+limit+switches&gs_l=img.3...1934.11028.0.11172.30.17.0.13.0.0.110.1260.16j1.17.0...0.0...1ac.dvlW_xxISWw

If the water is fresh you will be able to submerge normal micro switches with little problem assuming low voltages (5 or 12 volts) used.
frankswamper (author)  rickharris2 years ago
ok so i can use the micro switch underwater with no problems then? i looked at the link you provided but still havent grasped it... as far as i know the switch is a momentary button correct ? so how would it power the motor when my stops back off to head the other way to my other switch would i get power in that direction to motor ?
Because most of the many circuits my google search link takes you to use a couple of relays to keep the motor turning in the right direction once it has reached the limit switch.

In principle it is possible to do this with just switches but the right type will be very hard to find and or make. you need a couple of double throw double pole latched switches.

These would be connected as if in a sort of 2 way switched lighting system such as you may have on your stairs allowing you to turn the light on or off at the top or bottom of the stairs.

Better use the relays
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frankswamper (author)  rickharris2 years ago
Ok is there a relay that you would recomend ? An in the diahgram u provided is that the best route to go? Sorry for so many qs. But havent messed with this kinda stuff in years
OK this should be the whole story.
In the diagram below - more or less the same as before just re-drawn to make it easier to understand.

The relays A and B are set up as an H bridge.

Contacts A1 and B1 will reverse the direction of the motor when one relay or the other is energised.

Contacts A2 and B2 are used to keep the relay on until the other limit switch is reached.

L1 and L2 are the limit switches - a standard micro switch.

A micro switch has 3 connections a common, NC - Normally closed and NO - Normally open. (normally means not pressed )

When the switch is operate it goes from NO to NC

The NC connections are used to break the relay line at the end of the run to turn off the relay and stop the motor. The NO connections then turn on the other relay to reverse the motor.

From here the cycle continues.

As shown the relay A is on (energised and the relay B is off) It is possible that this system can be stopped mid run and then neither relay will be on. To get things going operate one of the limit switches with your finger.

The relay needs to be a double pole double throw relay suitable for the voltage your using. The limit switches are suitable micro switches.

Because I don;t know our availability I can recommend any exact components for this but from the above you should understand what is happening and find something suitable.

motor rev.jpg
frankswamper (author)  rickharris2 years ago
thank yall so much for your help but not shure i grasp were my wires all run witch way im attaching a photo of the dpdt relay an micro switches i got since i have done messed to relays up lol but im givin it a shot so my last qs is if it anit to much to ask could you draw witch wire goes to what pole an were on the pic i attached stupidfy it for me lol i just dont wanna mess up another relay or my motor

thanks so much for the help
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