Subject:
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Re: multi-device output controller
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 26 Mar 1999 18:48:55 GMT
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Viewed:
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938 times
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Wes Matchett wrote:
> There are 8 levels of PWM, so fwd/rev for 4 devices is possible.
Are you sure? I wasn't, so I went looking. The NQC docs seem to imply 7 powers levels
plus off. Which, technically, is 8 levels of PWM, but if you use all of them, a motor is
running at all times. That is fine if you use another motor output to control the speed
(as you mention later), but not if an external battery box is being used. The application
where it is ok to have a motor running at all times will be rare. You could simply not use
channel 0, but why build it then?
> I originally wanted a
> separate power input to allow a full 8 levels for each device. This would allow the
> controller to operate ANY device designed for the RCX ports and not assume a motor is
> connected.
>
> I am also toying with the idea of using the PWM to operate a stepper
> motor. Having a range of PWM would be very useful in that case.
Would it?
> Now that I have brought up that topic, anyone know how to drive a stepper motor w/ RCX
> PWM?
Steppers are not usually driven with PWM unless you need to do some fancy torque
management. An example would be full current when stepping, and reduced power for holding.
As for moving the motor, it is pretty straightforward to assign motor phases to PWM
levels. With 8 levels (counting 0%), you can have 4 cardinal phases and 4 half-steps.
If you want to do without the second RCX output (and PWM), you can keep your half-steps by
making use of the fact that the outputs are reversible. If you want to have 2 steppers on
the same RCX, you will have to do this.
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Message has 1 Reply:
 | | Re: multi-device output controller
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| (...) I don't know how NQC drives the ports, but both rcxcc and the RIS software have separate controls for on/off and power level. I just tested setting all 8 power settings - motors operates for all 8. -Wes (25 years ago, 26-Mar-99, to lugnet.robotics)
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Message is in Reply To:
| | Re: multi-device output controller
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| (...) There are 8 levels of PWM, so fwd/rev for 4 devices is possible. I originally wanted a separate power input to allow a full 8 levels for each device. This would allow the controller to operate ANY device designed for the RCX ports and not (...) (25 years ago, 26-Mar-99, to lugnet.robotics)
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