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Need Help with dc motor bidirectional controller circuit. Answered

Hello all i need some help with driving 3 dc motors bidirectional with pots. Im looking at something like this that i can make that will drive 3 motors with 3 pots not just 1 here are the motors and im going for torque not speed. Thank You


Buy the kit x 3??

So you want the pot to control direction - or speed??

Direction is easier with switches or relays - Your looking for an H bridge. Speed can be controlled by Pulse width modulation on the supply line.

thank you for responding so fast

I'm going for direction and speed

buying 3 is a bit expansive

i will be using ps2 thumb joysticks as they have 2 pots on them 2 motors will run from one stick and one motor from another joystick adding a h bridge and switches i would have to go "up,stop,switch,down,stop,switch,left.exc

i need constant control of direction.
to give you an idea I'm building something like a cnc machine its going to be manually controlled by the 2 joysticks first stick is for up,down..second stick is for left,right,forward,back....so say i wanted a circle stopping to hit a switch wouldn't work.

Are you aiming for a joystick controlled router? If so have you considered a direct mechanical link between the X,Y gantry and a "joy stick" You could then follow a 1:1 drawing and the router would cut out the same. A pantograph arrangement would give you a step up or down. in size.

IF your looking for CNC type control then you would be better off looking at Stepper motors. they give you the precision along with direction of travel automatically. Second hand would do from printer or scanner etc.

Using a DC motor unless you have some kind of feedback - a finned disc or similar to show where the motor shaft position is you would rely on your eye for position control - This isn't very accurate as your reaction time becomes a serious hindrance.

X Y router.jpg

Yes basicly a joystick controlled router. im disabled and have no use of my arms so im building this drimal holder so i can use it myself. its lke the diy cnc in the pic below.  the motors are just to spin a threaded rod witch will then move the dremal in that direction. my eye is great for posision as the drimal is up top.

i thought about cnc style with steper motors but i want manual controll not pc and i have the dc motors i just need to run them bidirectional with pots.


I admire your intentions - Will the motor speed need to be variable?

Are you happy that when you push the joy stick the motor moves in that direction at a constant speed.

The the LM293D or similar would do the trick as Steve says if it will supply the required current for the motors.

The LM293 required its 2 inputs to be high/low to make the motor turn if they are both high or both low then the motor is stopped. Depending on which way round the high/low is determines the motor direction.

This would require a modification to a standard joy stick to make it work directly,

If I were to do this I would use a microprocessor (I would use a Picaxe personally) as the interface between a standard joystick and the LM293 rather than modify the joystick switches.

The LM293 can supply around 800 Ma.

motor control.jpg

now I'm even more confused sorry I'm new to electronics i know what i want it to do but only way i know is flip the wire trick.

i just need something that will do what the dc motor controller i linked does

In actual fact my original question about speed was leading up to suggesting you use a couple of micro switched to make a double throw double pole switch.

In the diagram the part between the switches is the joy stick you move to set the switches. When in the centre the motor is off when moved either way the motor turns accordingly. The X axis looks just the same.

micro switches.jpg

hey rick been awile but do you know how i can make a joystick like thing for this setup i have the little tak switches i just cant figur out how to make a stick for them to be pushed together?

I assume the switches you have are push buttons. That said you can try this. I have made these at school and they do work.

A simple bolt for the stick will do and the pressure plat can be anything stiff enough to press the switches.

To make the H bridge work you need to press 2 switches at once. SW1 AND SW4 or SW2 AND SW3


I'm still wighting for a word back from steve on the circuit progress

Ok the LM293 is a motor controller - (technically a quad comparator) It is a16 pin IC.

this IC is capable of controlling 2 motors and the left and right side are identical.

On the diagram you can see V2+ which is your supply volts - up to 15 volts max I think (see the data sheet for certain) the ground voltage is the negative side of the power supply.

The motor is connected where the M in the circle is..

The IC inputs are pins 2 and 7 to make it work these pins are either high (supply volts) or low (0 volts or ground). When one pin is high and the other low the motor turns in one direction - when the pins are the other way round (low - high) the motor reverses. When the pins are the same the motor is stopped.

All you need is to arrange for these pins to be switched from high to low - A joy stick with micro switches on it (or even just the micro switches connected as I have drawn will do that.

If you want/need to use an analogue joystick - one with a pot you would need to interface it via a cheap microprocessor. The Picaxe range will do it and save the need to learn/use C as a programming language, they are cheap and the programming system is free.

You may need to ask specific questions to progress further.

How many amps and volts


Yes basicly a joystick controlled router. im disabled and have no use of my arms so im building this drimal holder so i can use it myself. its lke the diy cnc in the pic below.  the motors are just to spin a threaded rod witch will then move the dremal in that direction. my eye is great for posision as the drimal is up top.

i thought about cnc style with steper motors but i want manual controll not pc and i have the dc motors i just need to run them bidirectional with pots.

You need to give some motor ratings, and I can make some suggestions for you. I'm thinking of an L293 full bridge controller, which is about 1A output, bidirectional, and cheap. 2 motors per chip, hardly any extra bits needed.


all i know about the motors is this and here is what im wanting but for 3 motors pdf is here  maybe modifying 1 to run 3 motors?

sounds like what im looking for bidirectional cheap

The 293s should suit you fine. The cheapest way to do this is probably an arduino to read the pots in the gamepad, and then output PWM to the L293 for you - I reckon 70 USD in parts, tops ?

I'll do you a PCB if you'd like.


the kit i put up would cost the same for 3 and i dont own a arduino so it would be even more.

heres pix of joyticks ill be using they have 2 pots and 1 tack button in them


Nah, my component price included the arduino.

Sorting out a suitable "dead band" for the joysticks, so your cutter doesn't drift off on its own etc means you really could do with some processing in there.


Actually, around 10 bucks for the 293s, plus not a lot else apart from a arduino processor chip - you don't need the rest of the board.


im a little lost now

you sayin buy arduino,293s take parts off arduino add thim all to a new pcb?

Its complicated. Arduino is an eco-system that links a cheap processor, a development environment, and some more expensive PCBs sold by other folks.

All you need is the chip at the heart of it all, the processor is about 5 USD. And the 293s


ok so were lookin at like $20-30 to make the 3 motors run bidirectional from 3 pots like that kit right?

Yes, but the three kits wouldn't work like you're likely to need, so this will be better....

Might be. I can't see if it has PWM outputs and on board ADC though.


bummer been trin to find a use for it

so do you want to build this for the 3 motors and i pay you or you can direct me to the parts i need and what to do and i can build it?

my last circuit you helped with works great!

i looked up the L293D and atmega chip on arduino uno now i kinda understand.

Yes, its a nice thing, but it hasn't got what you need here.

I'll try and put a circuit and PCB together for you in the next week or so - have it on me.

Good to hear your other projects doing well !


looks good. im glad you know what your doing. i could never do somethin like that.

is the 9 hols on right the 3 pots and 6 holes on left the 3 motors am i reading that right?

Well done.

The red squares are where the motor driver chips go - I found some for 5 bucks each, virtually all the rest of it is a standard Arduino and its programming connections. You'll be able to set this up with a PC

hey steve havent heard from you in a while everthing still going ok, any new progress?

I'm waiting to send your board off in a prototype batch I need to run at work, but I've been out of the office in Germany for the last week unfortunately, and I have to go to Korea at the end of next week.


hey steve whats up how are things going havent heard from you in a while have you gottin it through prototype yet

Just back from Korea and up to my eyes in problems with family and work.


oh waw been traveling the world. thats cool i was just wondering what was going on thought maybe you forgot about me sense i haven't heard from ya in a while.

so will i need to program it cuz i know nothing about arduino or programming as you can see im still trying to learn the hole schematic thing.

I'll put the basics together for you, you can see how the code works, and later play with it. I ought to do the circuit diagram too....

coo if you could just program it so i can just hookup the pots and motors and use it thats all i need.

but speaking of programming what all could i do with this thing besides run the 3 motors

could it be hooked to a pc and controlled by software

what power supply will i need to get for it

will it run stepper motors

just trin to get an idea what its capable of incase i plan to play with it in the future

Yes, it could be controlled with software
No, it won't run steppers.
If the motors are 12V, then a 12V supply is all you need.

coo maybe down the road i will play with it and see if i can make EMC2 or something like it to run with it.

what amps would you recommend im thinking 1amp but not sure.

Well, I've reckoned on 1A in the design !

To run with EMC2, you'd need some positional feedback or steppers.


woohoo im right again lol

oh i see well it was a thought.

how is it coming along?