ROBO1 robots?


In
a
simply
Now, this is really interesting. I've never dug into the servos, but given this info, I can see why they get wimpy with 40-50 msec update. I can easily set my servo controller to shorter update periods, so I'll play around some more and see what happens. I suspect this could be useful with a servo-powered mini-sumo when you need some xtra oomph during the tussle [don't tell Dennis, his sumos win too often already].
- dan ==========
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dan wrote:

I think it would be possible to provide your own electronics and loop closure for standard RC servo mechanics. Use the servo's pot and motor and an external microcontroller with a multichannel A/D to read the pots and perform PWM Generation for many servos. A number of microcontrollers have multiple timers or better yet multichannel PWM generators. One amp H bridge IC's should provide adequate drive to the motors.
I am familiar with the Freescale dsp56800 family and I think that you could run at least 6 servo's on their controller with a single PWM generator (their PWM Generators output 6 channels each). The dual PWM controller, dual A/D chips like the DSP56807 could probably run 12 servos. I am currently building a 4 channel controller for a different system with the DSP56807 and I think that it the cpu horsepower, RAM and Flash space to do this.
Bob
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Si,
The '807 eats servos for breakfast. Don't forget that the internal electronics include a bridge. A bit of copper, a simple loop, and you can even make a springy feeling servo...

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MetalHead wrote:

I've seen people rip out the innards of standard servos replacing it with custom control (say a H-bridge and a little AVR). Much more important that the obvious much better control over torque and speed is the fact the it enables feedback about current position, current torque, etc. Not very useful for RC, but very very useful for walkers.
$0.02, Tommy
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Tommy Thorn wrote:

Nice idea, I had not even thought of that aspect of it!
Bob
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Dan,
[snip] : Now, this is really interesting. I've never dug into the servos, but : given this info, I can see why they get wimpy with 40-50 msec update. I : can easily set my servo controller to shorter update periods, so I'll : play around some more and see what happens. I suspect this could be : useful with a servo-powered mini-sumo when you need some xtra oomph : during the tussle [don't tell Dennis, his sumos win too often already].
<grin> Been there, done that. I now yank the guts and drive the motors directly, even more power there. ;-)
: - dan : ==========DLC
--
============================================================================
* Dennis Clark snipped-for-privacy@frii.com www.techtoystoday.com *
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Dennis Clark wrote:

but
update. I

I'll
already].
motors
see the other thread.
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You could add a little PIC or Atmel to an analog servo to increase the update rate. Use 1 line from the controller to give the PIC info using a simple digital protocol and you're all set. Would be <$1 per servo.
Mark

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So does anyone else believe, perhaps wrongly, that when robots do finally crack the home market you'll be able to pick up the same $30 servos off of Ebay for 3 for a $1?
I can dream can't I? :)
BTW, the Robix USB UsBor controller is a really nice way to roll your own servo cluster type robot. It's about $200 for the controller alone. It comes with a Java client-server architecture that makes it easy decouple the motor control from the physical PC location and chain controller's together. In addition, it gives you "motor strain" values for each motor.
I'm just a customer. I assembled a 6 DOF arm using the UsBor and also did some minimal work controlling it with a P5 virtual reality glove.
If you're interested: http://www.robix.com /
--
Thanks,
Robert
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finally
off of

They sell these these by the gazillions - at least the analog type - for use in model cars + planes - so doubtful we'll see much price drop.
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wrote:

I've got a website detailing progress on a bot I've been building. It's at:
    http://home.earthlink.net/~apendragn/biped/index.html
You basically have to use high torque servos. I used low-cost HS311 servos and they didn't have enough torque to allow the robot to walk.
The HS5645MG are the recommended servos because they're powerful enough and they generally cost ~$60 each.
I've got 12 DOFs in the legs (six each side). I've got a board set that I've been experimenting with and everything is onboard. For control, I've got an ATMEGA32 to generate motor sequences.
Ed L
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