Subject:
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using PWM output to control Lego motors
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Newsgroups:
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lugnet.robotics, lugnet.technic
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Date:
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Wed, 2 Feb 2005 16:23:32 GMT
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Viewed:
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1457 times
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In my ongoing quest to control Lego robots by radio, I've uncovered some
receivers made by GWS that work with a standard model airplane transmitter, and
have 4 channels of standard PWM (pulse-width modulation) output. For example,
see
<http://www.aeromicro.com/Catalog/gws_4-channel_pico_receiver__futaba__788636.htm>.
But now my ignorance of electronics is tripping me up a bit, so please bear with
me. My understanding is that the RCX uses PWM to control the speed of the
motors. So, it seems like I could use the PWM signals from this receiver to
control the Lego motors too -- right? If current or voltage is a problem (which
it probably is), then could I use the PWM signal from the receiver to drive a
photocoupler or solid-state relay or some such, which in turn sits between the
Lego motor and batteries?
This sounds to me like it should work, but I hope someone with a better
understanding of PWM and Lego motors will chime in.
The main problem I foresee here is that you would only have forward, no reverse.
Any ideas on how to tackle that problem? One thing to consider is adding an
"electronic speed controller" (ESC). A variety of these are available for both
brush and brushless motors (which type are Lego's?), such as these:
<http://www.aeromicro.com/Catalog/esc_for_brush_motors_107403_products.htm>.
But it's not clear to me exactly what these ESCs do: what are the inputs and
outputs? Are they useful for Lego purposes? I haven't been able to find any
technical data on them. Any insight would be appreciated.
Thanks,
- Joe
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Message has 2 Replies:
 | | Re: using PWM output to control Lego motors
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| Hi Joe, (...) are you sure this isn't for servos? (...) Yes, the RCX uses PWM for power control, in each 8ms period power is on for 0-8ms and off (disconnected) for the rest. (...) You need 9V and up to 500mA. (...) I have the impression that they (...) (20 years ago, 2-Feb-05, to lugnet.robotics)
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