Subject:
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Re: RCX and R/C combined
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 8 Apr 2005 22:55:17 GMT
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Viewed:
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1134 times
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In lugnet.robotics, Steve Lane wrote:
> I've just been experimenting with my RCX to see if it can sense the output from
> the Lego RC unit.
>
> The experiment was fairly successful, I was just wondering though if putting 9v
> into a sensor port does it any good. Are their any risks in making such a
> connection?
>
> I got a beep when I applied negative current.
>
> Any thoughts?
>
> Steve
Here's a diagram of the RCX sensor port circuit:
<http://www.brickshelf.com/cgi-bin/gallery.cgi?i=1067044>
Feeding a voltage of up to +9V (or the RCX battery voltage) will not harm the
port, as this is what it uses in Active mode (light or rotation sensor). You
can actually use an external 9V power source with a sensor in passive mode
(touch or temperature sensor), since the port will measure the voltage as a
proportion of 9V, just as it does in active mode with its internal current
source.
However, I recommend limiting the current of an external source to 15mA per
port, which is the same value as the internal current source.
If you set up the port as a temperature sensor and set the choosing threshold to
correspond to a voltage a little lower then 9V, it should work.
Using a Cybermaster (with built-in RC) it would be possible to have the motor on
its port B turn a light sensor for the RCX at different speeds so that the RCX
could pick up one of eight commands by RC control. The Cybermaster's
disadvantage was that its ports wouldn't run light or rotation sensors but using
an external 9V source these could be implemented. The Cybermaster has 5
sensors, 2 of them being shaft encoders for the two internal motors. If you
have active sensor functionality on a Cybermaster, you wouldn't need an RCX,
unless your program was long.
I rigged up an RC robot with the first RC car chassis, with its rear wheels
driving a rotation sensor and its front wheels pressing switches when it
steered. An RCX then read these sensors and moved two sets of motors in tank
drive, moving a walking robot.
BTW if you're using the RC receiver to command the RCX, don't expect the RCX to
be able to drive the RC car motors with enough power. See here:
<http://www.philohome.com/motors/motorcomp.htm>
I recommend some sort of RCX power interface, a bit like this (not a finished
circuit): <http://www.brickshelf.com/cgi-bin/gallery.cgi?i=915453> This would
need an extra set of batteries though.
Mark
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Message has 1 Reply:
 | | Re: RCX and R/C combined
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| (...) snip (...) I'm only intending to use standard gear motors. Great answear Mark, that's exactly what I wanted to know. Steve (20 years ago, 9-Apr-05, to lugnet.robotics)
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Message is in Reply To:
| | RCX and R/C combined
|
| I've just been experimenting with my RCX to see if it can sense the output from the Lego RC unit. The experiment was fairly successful, I was just wondering though if putting 9v into a sensor port does it any good. Are their any risks in making such (...) (20 years ago, 8-Apr-05, to lugnet.robotics)
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