Need help with the wiring diagram

I have 2 Limit switches, 1 6v DPDT relay, and a motor.  By using a timer, I would like to reverse the direction of the motor when it reaches the respective limit switches.  Can someone help me with my connections.  I numbered all the terminals so you can just tell me 3-5, 6-2, etc.  Thank you so much in advance. 

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uamusa (author) 2 years ago

thanks for all the replies. I found a different way with no extra parts. Jumper 11&16 and 12&15. 10&14 to motor. Constant power to 12&16. Timed power to 9&13..... This alternates the polarity to reverse the motor. Limits just go between power and motor.

-max- uamusa2 years ago

I see you got it working already though, good. Though before I read that, I have thought about it, and I think I have come up with an interesting solution, although I have NOT tested it or anything. I may actually build it sometime and see how it works. Maybe you can also give this a shot:

The idea here is that I have 2 DPDT switches, the 1st one will be a latch, and the second one will change the polarity of the motor. There is a giant RC circuit on the output of the 1st relay which delays the changing of polarity to the motor using the 2nd relay (as an H bridge), and the limiting switches control power to the motor in one or the other direction, (so when one limit is hit, the power cannot continue to go into the motor to make it keep trying to push the switch off, but still allow the polarity to be reversed and let the motor travel the other direction. Thats needed because the same RC circuit which delays the polarity switching is 'laggy' and the capacitor takes time to discharge.)

I am still thinking about the functioning of the circuit, tracing through the paths and different possibilities, basically 'simulating' it in my head, since I am too lazy to get the parts to make it.

arfon2 years ago

You need more parts... You want a flip-flop (IC, transistor or relay, it doesn't matter) and the motor circuit here-

relay motor controller.png
arfon arfon2 years ago

Here's with your numbers ASSUMING THAT 10 & 14 ARE THE NC CONTACTS

relay motor controller 2.png
iceng arfon2 years ago

In my experience with that style of relay,

The swingers are often pins 12, & 16 easily ohmed out.

arfon iceng2 years ago

Yeah, I'm just worried by his question that he is new to electronics (no offense meant).

uamusa (author)  arfon2 years ago

I'm only working with 6v. I wasn't too worried with frying myself.

arfon uamusa2 years ago

You need to do what iceng said and use an ohmmeter and determine which contacts on your relay are NC and which are NO. Take the ohmmeter and measure between pins 10 & 11 and then measure between 11 & 12.

If 10-11 are shorted => 10-11, 14-15 are NC and 11-12,15-16 are NO

If 10-11 are open => 10-11, 14-15 are NO and 11-12,15-16 are NC

My drawing above with pin numbers were just a guess, use what you actually find instead.

uamusa (author)  arfon2 years ago

so in this pic the 10&11 as wll as the 14 & 15 are connected to the NC & Com on the limit switches right?

arfon uamusa2 years ago

No, there are no limit switches in that drawing, it only shows the relay and motor connections. Since you have only two Normally Closed (NC) limit switches, you need to build/add a flip-flop circuit (see my drawing below).

If you don't want to use expensive relays for the flip-flop, you can buy a single IC. Look for a Set Reset (SR) Flip-Flop.

uamusa (author)  arfon2 years ago

I'm confused on the coil looking symbol on 9&13. What do I do there?

Now I wonder where you got that Idea... :P


This method will work fine provided you motor's casing isn't acting as a ground, (Like a starter motor) If it is then just mount it with rubber screws :)


That's been the standard way to wire a reversible motor to a relay for over 100 years...

Your drawing looks correct too. :)

iceng2 years ago

Here is a single relay (3PDT needed) and the elements of your sketch.

arfon iceng2 years ago

That may work for him but, his parts pictures show the limit switches are NC momentary switches. I ran into that problem also with my many solutions that I posted and then deleted.

arfon2 years ago

Here's a complete circuit with 2 additional relays, a resistor and capacitor. The resistor and capacitor is needed so when the power is applied, it will start in a determined state. The resistor's value should be as high as possible but still maintain the relay's hold current.

rev relay motor controller.bmp
arfon arfon2 years ago

To calculate the resistor you need: coil resistance (Rcoil), Hold Current (Ihold), and supply voltage (V+).

Resistor = (V+ / Ihold) - Rcoil