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forward and reverse variable motor circuit

donkey

Feb 26, 2011
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Feb 26, 2011
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hey guys, am making a r/c to make life easy to start with it'll be wired just to get the thing working, I'll go wireless later.
the design is for a tank. i was looking at making each side independant but i want forward and reverse, and I want to control speed. I was hoping rather than having a pot for speed and a dpdt centre off for direction I could get a circuit design to use a variable resistor so that when its centred no movement, push forward it slowly accelerates up to a top speed and pull back it reverse slowly until all the way back where it reaches its top speed.

this may seem simple and I was looking at power drills for ideas but for the control of this tank i want it simpler. any help will be greatly appreciated.

am looking at making the rc run of 2 7.2v lipo packs for now, one for each side. thanks in advance
 

duke37

Jan 9, 2011
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Jan 9, 2011
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5,364
Electric wheel chairs have a joystick which contains two potentiometers to control the two wheel motors. The sum of the voltages comming out gives the speed and the difference gives the turn. I forget the actual circuitry.

A similar control is used to steer planes. In the original design of tail, one control did up and down and the other left and right. Now some planes have a V tail which does the same job with somewhat different logic.
 

timothy48342

Nov 28, 2011
218
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Nov 28, 2011
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What about instead of a circuit to do this, go for a mechanical solution.

Get a hold of a couple slider-style var pots.
slidepot.jpg


Tear apart one end of each open, so that the slider can come out. Discard one slider, and attach them so that the remaining slider can glide from one track to the other. You'll have to bridge the tracks, too. I think there would be a low resistance stip(metal) and a high resistance strip(maybe carbon) and you'll have to build an insulating block for the slider to ride on as it jumps from ine to the other.
slidepotendtoend.jpg


Then your schematic is real real simple:
motorcontrol.jpg

I know it looks like the two var pots and two batteries make a complete circuit, but they don't. When the slider is in the upper track, the "B" connection is broken, and when the slider moves to the lower track, the "A" connection is lost. You would want a short gap where the slider is insulated from both tracks in the middle, so that both "A" and "B" disconnect.

I know this doesn't lend itself very well for going wireless. For that you might take a look at the way r/c cars work. I can't imagine they have a whole seperate control for reverse. Maybe they have a switch or something. I don't know.

--tim
 
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