HOW TO: Wire a DPDT rocker switch for reversing polarity

Step 5 UPDATE: Wiring Diagram

I've had a number of people ask me about a wiring diagram, as the photos may not be enough on their own.

Troy
http://www.FirgelliAuto.com

Comments

[whizzlord]

 Hi! i want to use a micro switch to reverse the polarity on the dc motor instead of using a dpdt rocker switch. please advice me on what to do. a circuit diagram will be highly appreciated.
Thanks!

[department_g33k]

Troy, I think your wiring diagram is either lacking "COM/NC/NO" labels, or is reversed. I've used this scheme myself many times, and that diagram looks like the NC and COM terminals are backward. The one I've used is: Supply (+) to NC(a) and NO(b) Supply (-) to NO(a) and NC(b) Actuator (+) to COM(a), and finally, Actuator (-) to COM(b). Thanks for posting!

[kapluf]

PS.: I was intending for the motor to be stopped or off whenever the lever is in the center position and for the lever to make it go clock or counter-clockwise depending on which is depressed, like a remote control for a rc car.

[kapluf]

I realize your comment was made year and a half ago, however I have a problem with your diagram and it would be nice if you could help me solve it. The problem is that I've got two switches such as the microswitch on the special switches section from this page http://www.kpsec.freeuk.com/components/switch.htm. they're setup one facing the other with a lever in between both, the thing is that when none of them are depressed the motor runs and by depressing either one of them it stops. Thanks in advance for your advice.

[mankhandelwal]

thanx to d labeled circuit diagram fom::::department_g33k

though the basic diag too is well undrstood

[department_g33k]

(removed by author or community request)

[department_g33k]

Troy, I think your wiring diagram is either lacking "COM/NC/NO" labels, or is reversed. I've used this scheme myself many times, and that diagram looks like the NC and COM terminals are backward. The one I've used is:

[Troy (Firgelli Automations)]

Maybe there is rocker switches out there that default back to one connection (I guess the NC in your diagram here). The rocker switches I use, and was thinking about is where they have a middle off position, and then two other positions, say 'up' and 'down'. And it certainly could be wired the way you show, it all depends on where you put the jumper wires and the connections to the power and actuator. When the switch is engaged both my circuit diagram and yours would have the same effect, the polarity going to the motor gets swapped depending on which way you push the switch. The middle poles are either connected to the two poles on one side or the other, so the end result is the same.

[department_g33k]

 Troy, after looking again, you're right.  Most I've seen have the markings, but I see what you're saying.  Thanks for the excellent post!

[kapluf]

I would really appreciate if you could help me with the problem I explained to department_g33k, thank you!

"...I've got two switches such as the microswitch on the special switches section from this page http://www.kpsec.freeuk.com/components/switch.htm. they're setup one facing the other with a lever in between both, the thing is that when none of them are depressed the motor runs and by depressing either one of them it stops. Thanks in advance for your advice."

[Troy (Firgelli Automations)]

Sounds like you're making two external limit switches for a motor. One to stop the motor in one direction, the other to stop the motor in the other direction.

If this is what you are meaning to have, this diagram may help..  you need to have a diode on each micro switch between the Common and Normally Closed.  When the micro switch is depressed it will cut the voltage to the motor, when you reverse polarity to change direction of the motor the voltage can't flow through the micro switch because it's cut the circuit, which is why you need the diode (basically.. a one-way gate for electricity).  So when you reverse polarity the voltage will be able to go through the diode and move the motor off the micro switch. 

www.firgelliauto.com/images/actuator-with-two-limit-switches.jpg

If this isn't what you're doing, let us know and I'm sure someone here can help sort it out..

[department_g33k]

 Kapluf, I'd love to help, but I'm going to need more input on how you've got your switches wired.  The URL you provided shows a basic SPDT, which is essentially half of the switch described in this post.

I'd be careful using two SPDT switches instead of one DPDT, in some scenarios if the mechanical link fails, switching only one of the two micro-switches could give you a dead-short!

That said, I'd take a look at the diagrams again and make sure your wiring matches.  Basically, you want the motor to be powered off the "COM" or Common poles of the switch.  Then run power to the NC and NO posts, making sure that you reverse polarity when you hook it up to one set.

Maybe post a basic diagram of how you've got yours wired?  I'd love to help, I just need more input!

Also, just out of curiosity, what're you making?

[kapluf]

Hello to all and thank you very much for your quick answers. I am building a remote controlled car as a small w-e project, even though it is not wireless yet. I actually have everything wired and installed and am working on the conroller which is a dual action two levers, one for gonig forwards-backwards and one for the steering (they're both plain and simple 9-12v dc motors with two NiCd 6v 1000mA batteries set up in series for the 12v needed, no servo since it is very hard to get where I live). I've got four switches (two for each lever). I inicially tried department_g33k's wiring diagram and what happened is that both motors would stay on when neither of the switches was depressed. Whenever I depress either of them it would stop the motor for that particular set. I haven't tried Troy's diagram but I can see that the effect is going to be similar if not the same. I am about to try a new setup I came up with a friend of mine and I'll tell you about it when I'm done. I'll try to upload a few pictures when I get home so you can see what I'm talking about. Thanks again for your help!!

[department_g33k]

The one caveat of using SPST switches (NC/NO/COM) vs. Troy's diagram is that you don't have on/off control, just direction.  Troy's diagram, using switches that have a middle (off) position allows full control.

Alternatively, you could have a second set (this time with just 1 switch for each axis) that's just on/off, and you'd pass either positive or negative through the switch.

Hope that helps.

[kapluf]

Well, I'm back home and I just finished making some research.... It turns out that my 2 switches setup isn't going to do the trick. The thing is that the switch mentioned by troy stays in the position you select and I need it to go back to OFF position when I release it, so first thing in the morning, I'm going to the hardware shop and get some proper switches and redo the controller... I can't thank you guys enough you've been most helpful!!

[department_g33k]

 My pleasure, glad the instructables community was able to help!  When you're finished, you should create an instructable with your project!!

[kapluf]

Just so if anyone is interessed in something like this, I solved the problem by making two arrays of two spdt switches per lever, from which I removed the NC contact, therefore making them spst and it made it so much easier!!

[kapluf]

I'll do that as soon as I finish the project, what I CAN do now however, is to recommend this small program that helped me design my diagrams pretty quickly and easily, it's called circuit maker 6 student edition, it's a freeware (even though it is not backed up in any way by the maker anymore), and it can be easily found on google, and one last time thanks to department_g33k and troy for all their help whitout which I couldn't have come to my conclusions this fast!!

[peterdepue]

Troy, great diagram for the switches I purchased at my local hardware store. Took me 30 mins to wire up two motors. They work great. Thanks for the posting