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
Reply to
pogo
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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
Reply to
dhylands
Try here... This might be what you need. Good luck.
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Reply to
Robert Davidson
is
asking
thought I
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PWM.
magnitude, or
normally used
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great!
and an
Thanks for the great explanation! This one goes in my notes folder ! Thanks again. JCD
Reply to
pogo
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Close, but not enough amperage for my needs. (which I didn't put in the specs, either) Thanks though ! Good stuff there .... JCD
Reply to
pogo
Its a little more than $100, but the serializer from
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will handle 2 dc motors and a couple servos, as well as sensors, and you talk to it via the serial port. Ringo
Robert Davids> Try here... This might be what you need. Good luck.
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Reply to
ringo.davis
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.
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Reply to
Si Ballenger
port.
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
Reply to
pogo
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:
Reply to
ringo.davis
spit
Thanks Ringo. Do you used to go to BotLanta (AHRC) ? Seems like I recall your name. Anyway, thanks again ! JCD
Reply to
pogo
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
Reply to
Randy M. Dumse
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
Reply to
pogo
nobody seems to have mentioned the osmc
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you can build it yourself, we have.
dan
pogo wrote:
Reply to
rue_mohr
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.
Reply to
RMDumse
winning
and
IsoMax(TM)
Thanks !
I'll be taking a long look ! JCD
Reply to
pogo
Yep, Still do. Ringo
pogo wrote:
Reply to
ringo.davis
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.
Reply to
D. Jay Newman
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
Reply to
pogo
Just took a look at it. Also surfed over to the Scorpion XL page ... now *that* might be exactly what I need ! Thanks ! JCD
Reply to
pogo
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zwgearbox

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