polarity reversing with relays for 12vdc

Hope you can help me. I am building a project in which I require a low speed dc motor (12v) to have its polarity reversed every time the power is turned off, then on again...
on (clockwise) - off-on (counterclockwise)-off-on(clockwise) etc.
I don’t want to use a switch, just replays and run the 12v from the acc from my car.

thanks in advance!

PM OLDSPARK or DUALSPORT They are the ones for this.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

How big is the load you are trying to switch? Once power is turned on do you want it to stay on until the power is turned back off or does it need to time out at some point? What is your budget?

What is it the motor will be doing?

-------------
Kevin Pierson

kpitao wrote:

---

I don’t want to use a switch, just relays and run the 12v from the acc from my car.

---

Assuming you don't want any relays to be energized to retain settings when the car is turned off, you'll need to use something more than just relays alone.  It could be done with a simple solid state circuit to act as a memory of the last state, and toggle states each time the power is switched on.  The circuit would be used to control the relays used for the polarity reversing, powering the motor.

As Kevin indicated, more details on how you want it to work would be helpful-  it sounds like you just want this motor to run for as long as the car is switched on, but if you need a specific run time and then turning off, it would make the circuit more complicated.

If you really want to use just relays, then you'd have to put up with energized relays while the car is off, which could drain your battery.  Or use specialized relays that can retain states, which aren't as readily available.

Thanks for the replies!

 1. Load is not big at all; around 4lbs.

2. That's right once power is turned on stays on until the power is turned back off.  No need to time out at any point?

3. I don't want drain my battery.... so you're saying that I should use Latching relay?

4. I can also use actuator instead motor.

Thanks

Whats the load of motor (ie how many amps does it pull)?

Just to clarify - each time you turn the ignition on you want the motor to spin the opposite direction? And when the ignition is off you don't want the motor to do anything?

-------------
Kevin Pierson

Just FYI since your problem appears solved....


(from momentary to latched output).

That does not help me at all.

Maybe I'm not explaining well.

Simple task (I think)

I'm using an actuator now, Firgelli L12 b 

While voltage is applied to the motor V+ and ground leads, the actuator extends. If the polarity of this voltage is reversed, the actuator retracts.

This is what I need:

When I turn my car on 12v is sent to the relays to provide 12v and ground to the correct lead of the actuator.

Now when I turn off my car the relays sends both 12v and ground to the inverted lead of the actuator.

Just look at 5 wire or relay interrupt locks in the relay section. You might want to add a timer, can't have the relays drawing juice when the engine's switched off.
Two relays and a timer circuit will do this. Just use the ignition circuit to trigger the relays and timer.


-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Ground terminal 85 of both relays.  Connect an ignition power source to terminal 86 of both relays.  Connect one motor lead to terminal 30 of relay A.  Connect the other motor lead to terminal 30 or relay B.  Relay A as follows, Power to terminal 87.  Ground to terminal 87A.  Relay B as follows.  ground to terminal 87A, power to terminal 87.  If the device works opposite of the way it needs to work, switch the 2 motor wires from relay A and B.

So how will it reverse when the ignition is turned off?
For the second relay use a 528t timer relay as follows:
Ignition to black white.
12v+ Constant to red and brown, fused at whatever the motor's rating +2amps. Share this fuse with the other relay (terminal 87)
Ground to orange and black.
Yellow to motor wire.
Set the timer for 1 second longer than the motor's time.
This will save your battery.
N.B. You could always salvage the timing unit from a late Hirschmann 6000 or Bosch Autojet antenna.



-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Howie, thanks for the question.  I knew that if you could not see how it worked, there must be a problem.  I went back and read my post again.  Then I saw the problem. 

EDIT  In earlier post, Relay A should be as follows.  Power to 87 and ground to 87A

Relay B should be ground to 87 and power to 87A

In the earlier post I inverted the order of power and ground connections.  But did not invert the data for those connections.

Point taken Craig, just that I won't assume internal limit switch based on the poster's (lack of?) knowledge, thus a timed relay when ignition is shut down. Come to think of it, if no limit switches one would need 2 x 528t timers to be safe.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Just saw your last post, NOW I see it!
It's actually a very simple question, just not posed in a straightforward manner, always half the battle.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thanks for all the replies. I will try tonight. and I will post the outcome.

Without any timing control from the relay circuit, your actuator will be powered up continuously whether the car is on or not. Your actuator will have to have limit switches to cut power on its own.

Is this actuator you're referring to a simple power antenna or equivalent? You want it to extend when you turn the ignition on, and retract when you turn it off?

That isn't how you described it originally, which suggested power was to be applied when the ignition was turn on, and the polarity reversed each time the ignition was cycled off and on again. That was the reason behind the inverter circuit like Oldspark suggested.

Back to my comments about using 2 x 528t timer relays instead.
Else flat battery and/or burnt out motors.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.