# Looking to design a cheap motor controller



## Retroplayer (Feb 22, 2013)

First of all, greetings! I am new to the forum.

Many of my projects have involved hacking animated toys, etc... I have always had to build my own H-bridge drivers to run these as they often have more than just two motors. And every time I keep thinking, "Wouldn't it be nice to have a simple, compact 8-12 motor h-bridge circuit for this that I could just buy?" There are motor controllers and motor shields of course, but they are usually expensive, typically offer far more power than I would need, and usually only control 2 motors.
So I have been thinking about putting something together and looking for some feedback and suggestions. I am working on the design of an 8 to 12 motor H-Bridge circuit intended for low power motors like those found in toys and holloween type props (usually about 1.5A max, typically much much less.)
I could go a couple of different routes here. At first I was thinking of just a straight set of H-bridges with 2 inputs to each motor. But that would mean needing 24 IO pins for 12 motors. So, I started thinking about using logic to expand the IO. Then there is the idea of PWM for speed control. Most micros would not have enough PWM. And what about feedback and PID control, control for limit switches, etc...?
In the end, I am basically talking about turning a bunch of motors into servos, I guess. So then I figured why not just make it a servo controller with a Mini-SSC II style interface?
Anyway, my post is here to solicit feedback, suggestions, and to gauge interest. I also may need some help implementing it, mainly in the PID portion. I am really learning about that and have gotten it working with a single motor.
I have several other animatronics specific modules in mind, mostly a list of things I wish were just available and didn't to build every time. I am an electrical engineer, but not much of a programmer, unfortunately (well, not very good at it anyway.)


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## Retroplayer (Feb 22, 2013)

Well, apparently there is zero interest in such a controller. Hmm...


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## Otaku (Dec 3, 2004)

Hi Retroplayer,
Actually, I think that a device that can control large or small high torque DC motors, such as the popular wiper motor, would definitely be useful. I've developed some motor control circuits that allow basic control for a wiper motor using timers and limit switches (no polarity reversal switching). I use them for opening and closing coffin lids, but the control is limited to 180° rotations. I'd like to hear more about what you have in mind.


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## halstaff (Nov 18, 2009)

I'm always interested in the controllers others are coming up with. I'll be watching this thread carefully.


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## fritz42_male (May 5, 2009)

Turning decent size motors into servos is definitely of interest especially if you find a cheapish high torque motor to go with your board.


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## skidrow (Feb 21, 2013)

I am also interested in turning a dc motor into a "RC-type" servo motor but I am not sure if that is what you are talking about. In order to achieve that you would need some type of feedback from the motor that provides feedback on position such as a potentiometer attached to the motor shaft. Is this what you are talking about or just something that adjusts speed based on an RC servo pulse? If you are just wanting to adjust speed then there are already controllers that do that in the market. Parallax offers this one that only costs $50, accepts RC pulses for control and will handle motors up to a ridiculous amount of current.


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## Retroplayer (Feb 22, 2013)

Well, yes and no. The idea is to develop a board that acts like a serial servo controller (like a Mini-SSC II) but instead of attaching RC servos, you would attach your own motors and pots.

Specifically, I was talking about a board to power many low voltage/ low current motors mainly for use in converting store-bought toys and props into controllable items. There are lots of driver boards (expensive too) for high current motors.

More than one response mentioned a board capable of powering wiper motors. Hmm, building something like that directly drives up the cost, but it wouldn't be too difficult to go with my initial plan and have a module that plugs for higher powered stuff.

I hadn't considered that because there are so many high-power H-bridge drivers out there, but not really anything for those powering lots of small motors.


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## Otaku (Dec 3, 2004)

Ah, I see. With pshort's invaluable assistance, I have a LM358 op amp board in-process that takes a signal from a MP3 player and boosts it up to turn on a FET. I'm using it to drive the jaw motors in Gemmy-type talking skulls. It replaces the OEM board and lets you control the motor with the MP3 player so the skull says what you want it to. It doesn't actually servo the jaw motor, just turns it on and off. Is this kinda what you have in mind?


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## Nutz (Feb 19, 2013)

Otaku said:


> Hi Retroplayer,
> Actually, I think that a device that can control large or small high torque DC motors, such as the popular wiper motor, would definitely be useful. I've developed some motor control circuits that allow basic control for a wiper motor using timers and limit switches (no polarity reversal switching). I use them for opening and closing coffin lids, but the control is limited to 180° rotations. I'd like to hear more about what you have in mind.


Would something like this be of use? http://dormanproducts.com/p-33306-88136.aspx . This is a very cheap wiper pulse/delay module . Once again I am very new to this, just offering suggestions.


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## halstaff (Nov 18, 2009)

I was playing around with a hanging Pirate and used this Intermittent circuit to add a pause to his kicking - http://screencast.com/t/RJexisFoKqjX


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