looking for THE dc drive motor speed controller solution

Well I am frustrated. I thought had "THE" solution for driving my DC drive gear motors, but it appears that PWM from one device is
not the same as PWM from another. crap! ( or --- I am not asking the right questions / lack of understanding, etc ... ) I thought I had the perfect H-bridge device that I could control from either a Acroname Moto 1.0 module or Servo Controller module until I discovered (if I am interpreting the technical advice correctly) that I can't get the speed control granularity I want that way --- it sounds like I can only get near full speed that way.
Here are my specs:
The brains of the robot will be a mini-PC board (ITA, etc.) It will need to control a servo controller (like Parallax, Lynxmotion, etc. for arms/grippers/camera pan/tilt) It will need to control 2 reversable DC gear motors for differential drive and steering
I want as few external boards as possible, for power consumption, weight, etc. In other words, if I could get the servo controller to also send signals to the motor speed controller that would great!
Motor controller must be affordable (between $25 to $80 to control 2 motors; $100 MAX !!! )
connects to mini-PC board via serial port or USB gets commands from PC to set speed & direction & stopping OR will receive PWM signals from a PC-based servo controller one channel will connect to one 6-12VDC gear motor, reversable
Entire system will run on 12VDC, max. I *could* go to 24VDC if need be, but I really don't want to for obvious reasons.
Any suggestions ? Thanks ! JCD
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Hi JCD,
pogo wrote:

When you use an H-Bridge to drive a permanent DC motor, you use PWM. There are a couple of different types of drives (signed magnitude, or locked anti-phase).
With signed magnitude, you have two control lines, one is normally used as direction and one is normally used as the PWM control signal. The percentage of on time (or off-time depending on the direction) in the PWM signal controls the speed.
With locked-antiphase, a single control line is used. 50% duty cycle means stopped. Greater than 50% means move in one way, and less than 50% means move in the other.
RC servos also use PWM, but quite differently. With a servo, the width of the pulse typically vaires from 1 millsecond to 2 milliseconds. The spacing between the pulses is less crictical and typically about 50 pulses per second are sent out. A 1 millisecond pulse tells the servo to move to one extreme, and a 1.5 millsecond pulse tells it to go to the middle, and a 2 millisecond pulse tells it to go to the other extreme.
RC servos often contain a permannent DC motor (at least on the inexpensive servos). You can remove all of the servo electronics, connect the motors up to an H-Bridge and drive the motors just like regular motors.

You'll probably need one a servo controller to drive the servos and an H-Bridge to drive the DC gear motors.
Dave Hylands
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Thanks for the great explanation! This one goes in my notes folder ! Thanks again. JCD
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Try here... This might be what you need. Good luck.
http://www.robotshop.ca/home/products/robot-parts/electronics/servo-controllers/solarbotics-l293d-motor-driver-kit.html

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http://www.robotshop.ca/home/products/robot-parts/electronics/servo-controllers/solarbotics-l293d-motor-driver-kit.html
Close, but not enough amperage for my needs. (which I didn't put in the specs, either) Thanks though ! Good stuff there .... JCD
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Its a little more than $100, but the serializer from http://www.roboticsconnection.com/ will handle 2 dc motors and a couple servos, as well as sensors, and you talk to it via the serial port. Ringo
Robert Davidson wrote:

http://www.robotshop.ca/home/products/robot-parts/electronics/servo-controllers/solarbotics-l293d-motor-driver-kit.html
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couple
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Hey that looks slick! I'm not crazy about being limited to .Net to use their provided libraries, but I have an email in to thier tech support regarding that. But, yeah, I can handle more than $100 if one product takes the place of 2 or more others! Since it's serial I assume I can access/control everything regardless of libraries as long as I send/receive the correct commands with the right protocol. Of course, now I will examine the downloaded manual *after* I have written all of this.
But I did want to say Thanks ! JCD
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the .NET is just there if you want to use it. Anything that can spit out serial can talk to it, 232 or TTL.
pogo wrote:

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spit

Thanks Ringo. Do you used to go to BotLanta (AHRC) ? Seems like I recall your name. Anyway, thanks again ! JCD
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Yep, Still do. Ringo
pogo wrote:

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wrote:

You might get a servo control chip and a PWM chip from below and put them on a single small board. The bottom link shows how simple a servo control setup can be. For the PWM control of motors you would probably need some high current MOFET transistors in an H-bridge to rapidly turn on/off the current to the motor.
http://www.kronosrobotics.com/xcart/customer/home.php?cat)2 http://www.geocities.com/zoomkat/ezservo.htm
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What you're asking for is exactly one of the uses our 'Pod's boards were intended for. The DSP processor in the our 'Pod's were designed specifically with motor control in mind, and do the job very well.
The IsoPod(TM) for <$100 has 12 PWM outputs, and 14 timer lines. Configure them to be RC Servo PWM style signals, and you can control 26 RC Servos at once.
Or configure one PWM module (six lines) to control real DC motors, and control 1 (BDCM), 2 (Complimentary with enable), 3 (Complimentary), or (Independent with Locked AntiPhase) 6 motors. Still have 20 outputs available for RC Servo control.
Or with the PWM module as above, do two motors, and use quadrature feed back (loose 4 timer lines) and have have two closed PID loops. So you can do two beautifully controlled DC motors, and still have 16 RC Servos controlled as well.
Plus the language in the 'Pod's is interactive. Send command from the PC host via serial, or USB (we've got USB versions of the 'Pod's as well).
If anything, our 'Pod's are so good for motion control, and have so many options... it's hard to get people to understand the power they've got. Pair up our 'Pod's with our H-bridges, and just a little bit of software (we show lots of examples) and you really do have THE dc drive motor speed controller solution, par excellance!
Sorry to sound like a commercial, but this is exactly what I meant for these boards I designed to be used for. I'd be very pleased so see everyone come to understand how good they are at motion control.
--
Randy M. Dumse
www.newmicros.com
  Click to see the full signature.
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software
motor
Where exactly are the many examples you mention on your website ?
Also, regarding the pods, it looks like after I buy I Pod then I also have to buy additional software to do any programming. Is that correct or have I glossed over things too quickly ? ( I tend to do that, so please feel free to correct me! )
Thanks - JCD
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pogo wrote:

For the full blown PID example, go to our 'Pod's Downloads page. In the appnotes - Example programs shows actual code from a contest winning robot, also including Odometry.
There are quite a few RC Servo control examples there too.

Nothing extra required. 'Pod's come with IsoMax(TM) installed, and Small C available for free download. There are third party full development languages available, but really, we prefer our IsoMax(TM) over any of those.
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?
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IsoMax(TM)
Thanks !
I'll be taking a long look ! JCD
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pogo wrote:

I don't work for them, but I do like the 'Pods.
I also admit that they have a pretty bad website. I think that if Randy put the information that he gives us here on his website then there would be fewer questions.

Iso-Max (a Forth dialect with some interesting extensions) is included. This is a nice programming environment.
--
D. Jay Newman ! Author of:
snipped-for-privacy@sprucegrove.com ! _Linux Robotics: Programming Smarter Robots_
  Click to see the full signature.
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I'll agree on that! Might not be a bad idea to scrape some threads off here and post in a Q&A ! Randy has been a big help to me here in this group before I even ordered anything from them !
JCD
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nobody seems to have mentioned the osmc
http://www.robotpower.com/products/osmc_info.html
you can build it yourself, we have.
dan
pogo wrote:

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Just took a look at it. Also surfed over to the Scorpion XL page ... now *that* might be exactly what I need ! Thanks ! JCD
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