# R/C control of DC motor direction (NT)



## BillBrakeman (Jan 3, 2008)

This is not directly a train question. I have an application where I want to use an R/C set to control the direction, but not speed of a DC electric motor. I know two ways of doing it using servos, SPDT or DPDT switches & perhaps a DPDT relay, but I am wondering what it takes to do it digitally. 
Thanks for any advice you might give me.

Bill


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## Cougar Rock Rail (Jan 2, 2008)

Hello Bill, 

You could have a programmable microcontroller take the data from the R/C reciever to decide what direction/speed you were trying to achieve, then have it give the appropriate command to whatever you are trying to run. I'm sure there are simpler ways to do it though! 

Keith


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## TonyWalsham (Jan 2, 2008)

Hello Bill.

I am assuming that this application has nothing to do with controlling the speed of an electric motor from the same transmitter device. If it does that would be a different subject.

If not, here are the instructions for the R/C switching devices I sell.

http://www.rcs-rc.com/PDF/RC_Modules/Instructions/RC_Modules.pdf 

Scroll down to page # 9.

This shows how to control the direction of two motors. The 2 relay version would only be needed for one motor.
They use two SPDT relays to make one DPDT relay.
You can control them with any same frequency RCS transmitter.


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## Del Tapparo (Jan 4, 2008)

Bill - By "digitally", and your description, I am assuming you really mean how to do it using solid state devices? If so, then you are talking about an H-Bridge motor driver. They use 4 FETs instead of a DPDT switche or DPDT relay. These are available from robotics suppliers and R/C hobby lines. They are known as ESCs (electronic speed controls). They will control both speed and direction.

Tony - How does your unit interface with R/C? On board receiver or external? Looks like you would have to use two SPDT relays for motor reversal; 1&2 on for reverse,1&2 off for forward. Is that correct?


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## TonyWalsham (Jan 2, 2008)

Hi Del. 
The R/C modules are compatible with the RCS TX-24 and TX-4. Simply set suitable address codes. 
They can be used for all sorts of things. 

The relays are spdt. When used to control the polarity of a fixed voltage only one is on at a time. 
When *both* relays are OFF, (or ON), there is no output. 
One function ON provides one polarity of the fixed voltage. The other function ON reverses the polarity of the fixed voltage. 

I used to do the same thing years ago with two spdt micro switches mounted on a servo. The servo arm pressed the switches alternately as it rotated.


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## Del Tapparo (Jan 4, 2008)

Posted By TonyWalsham on 01/14/2009 5:23 PM
The relays are spdt. When used to control the polarity of a fixed voltage only one is on at a time. 
When *both* relays are OFF, (or ON), there is no output. 
One function ON provides one polarity of the fixed voltage. The other function ON reverses the polarity of the fixed voltage. 

I used to do the same thing years ago with two spdt micro switches mounted on a servo. The servo arm pressed the switches alternately as it rotated.

That would be your cheapest way to go Bill. Good idea Tony.

But if using your switch module would he have to buy a receiver also, or is it built into the switch module?


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## TonyWalsham (Jan 2, 2008)

The receiver parts are all built into the modules. 

http://www.rcs-rc.com/index.php?page_id=1020 

If Bill wanted to use a servo to do the job I still have some of the mounting brackets from 20 years ago around somewhere he could have for the cost of the postage.


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