HOW TO: Wire a DPDT rocker switch for reversing polarity

When you need to control a DC motor (such as a DC linear actuator) you usually need to be able to swap the polarity on the wires going to the motor.

A double pole, double throw switch is used for this purpose but you have to wire it up correctly to reverse the polarity going to the linear actuator.

Step 1 Required materials

You need the following materials:

-DPDT rocker switch
-insulated disconnect terminals (female) x 6
-wire
-wire cutter/crimper/stripper tool
-a linear actuator or DC motor to control

Comments

[drocto]

The center poles wiring is a tad confusing. "Similar to the last step take another wire that will go to the +12V DC..." for example as well as connecting to "ground". Also, the instructions are not explicit regarding wiring to the motor. Overall, thanks though.

[luneydude]

my dad knows alot about this stuff and so do i but im only fifteen and i wud have him help me but he leaves soon for fort benning, georgia for a year so youll have to bear with me here!!! this summer im going to build a model maglev train that runs recieves its power from a wind turbine im building and the wind turbine will power the electro magntes i want to build and put in the track. i want o be able to keep the car levitated but not moving when my system is off. i have a control panel devised to control the whole system and the track is divided up into ten sections. i want to go from the stepper motor in the wind turbine to a potentiometer to control the output of power to the rest of the system. the from the potentiometer i have it go to a switch the turns the whole system on and of and connects to an led to tell me if its on or not. going from the system switch i have it going to ten different potentiometers to control the power to each electromagnet. from those potientiometers i have them going to toggle switches one for each potentiometer that controls the power to the electromagnets in the track and they connect to leds to tell me if there on or not. each toggle switch connects to a section of the track witch each section will have at least 20 or more electromagnets. now heres where im stumbled... i want to be able to turn the electromagnets on and off, which ive already done, control their power level, which ive done, and change their polaritys from north to south at will, which i havnt done, and keep the car levitating while the electromagnets are off, which i havnt done. how will i connect from the section switches to a switch the will change the polarity of the electromagnets in each section and i want it to conrol every other electromagnet in the section so ill have to switches 1 for A magnets and 1 for B magnets how will i connect them to control the polarity? and finally how will i set the track up and system to keep the car levitating off the track while the electromagnets are off? oh yah and how will i build the electromagnets i was thinking of just running the current into small copper plates/peices to creat an electromagnet cause ive seen that be used as an electromagnet before and have done that in other projects but this is my most complex project yet and i want to do it right the first time around?... oh yah uhm each A magnet in a section will connect to each other and each B magnet in each section will connect to each other so keep that in mind when your figurin this out for me thanxs!!! so its such a long explanation just wanted to be as detailed as possible!!! :) thanxs alto guys

[luneydude]

also whats ground means

[Justdoofus]

Hey Luneydude. I am 15 years old as well, and I have learned all of this stuff from scratch, I knew how to do this stuff for 12 years. Anyway. Ground simply means the NEGATIVE (black) wire of your battery, or chassis in a vehicle. The only thing I know how to make via electromagnets are magnets that can lift up to 6600 lbs of weight with a 12 volt battery..

[recordmasta001]

Hi very usefull instructable. Would anyone know how to wire these so two switches can be used to do the same thing, similar to a light switch upstairs and downstsirs that both control one light??

[bhtre123]

That's called a three-way switch. Just google and you'll get it.

[kevlar19]

I know this is kind of old but I found it and it has been helpful but I'm still having a small problem. I have a DPDT switch hooked up to a DC motor with a Potentiometer in series to control the speed of the motor. The only problem is it only controls the speed of the motor in ONE direction. When I flip the switch to make the motor go in reverse, the motor just spins full speed with no control from the pot. Any thoughts? I can upload a diagram of how I have it wired but its an extremely crude diagram. I don't how to make a true electronic schematic with all the correct symbols.

[nigel da nautilus]

try putting the potentiometer in before the dpdt switch, so the power goes potentiometer --> switch --> motor instead of switch --> potentiometer --> motor

[pacificfurn]

Thanks so much Troy! It works great. I am using it to control a 12v. power window motor to raise and lower a shelf. I soldered in the switching diodes I purchased at Radio Shack to the limit switches. Bingo! It works... once. I'm afraid the amperage is too high to the RS diode. What do you think? Where can I get higher rated diodes? Mark

[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!

[lane29]

i am remote controling a powerwheels and i needed this wiring diagram forever                                                                                                        

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

[stoogman]

Hi there, thanks for that - what diodes do i need i'm using a superjack linear actuator (DC) and a 36volt power supply

[Troy (Firgelli Automations)]

Not 100% sure, you can go to DigiKey.com or Mouser.com and ask them for a diode that can handle > 36VDC and whatever amps your actuator pulls. I dont know which diode off-hand..

[stoogman]

Hi i want to use this to power an actuator with a throw of about 18" or so that will raise a tabletop platform - how can i introduce two limit switches to stop it at the top and bottom of its path of travel, i've tried sketching it out (so i dont reverse polarity anything) but i just cant get my head round it! Any help - especially in schematic form - would be greatly appreciated. thanks

[Troy (Firgelli Automations)]

You would have two micro switches with diode wired inline with the actuator motor.

[kewlkiwi]

If using a simple double pole-double throw (i.e.. two position) instead of using a 'center-off' type switch, It might pay to check that the contacts are described as 'Break-before-Make' and definitely not 'Make-before-Break' Using the later type would put a short circuit across the power supply each time the switch is toggled!

[billchuckred]

I have a question about dpdt switches. What happens when the switch is in the center position? Does the motor "hold position" or is it just off and freewheeling? Do I need a center on dpdt switch to hold the motor in position? Ive been surfing around and seen dpdt center on here and there..but I can't find any info as to what center on actually is...heh Obviously in a servo or gearmotor you would want the motor to hold position when the switch was centered Any light on this would be greatly appreciated

[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!!

[hpmori]

thanks for posting. Do anyone knows, are both the jumpers for reverse polarity. Which brand switch to use if I want one jumper for forward and other jumper for reverse. I know this will work, so need suggestion.

[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

[static]

I used a similar wiring to use 4 Ford starter relays to make a corded remote control switch for a 12VDC winch used on a pick up boom hoist. The reason I chose those in because I could walk into any supply store and buy them off the shelf, and at that time they where less than $5 each Yes the relays aren't duty rated for such use, but in nearly 10 years of daily use there were no relay failures. These days I would build a wireless remote in addition to the corded remote. The only way I can see how to improve your instructable is to add a wiring schematic to aid those anyone can't see how this actually works, to figure it out by tracing the current paths.

[burzvingion]

In his book, "Robot Builder's Bonanza," Gordon McComb has a lot of little tricks like this one. Most of the designs are outdated as the book was written in the '80's, however the concepts can be easily updated with more modern components. He also has several other books.

[Ian01]

I have the 3rd edition in my hand right now. It was published in 2006. Most of the stuff in it is common, but there are also things like fiber optic whiskers.

[burzvingion]

I have the second edition, which is really just a second printing of the original book. I looked up the 3rd ed. on Amazon, and it looks like a lot of time was spent updating it and adding new things. Perhaps its worth it for me to buy the new one, though I liked the old yellow-and-blue cover better.