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Subject: 
Re: multi-device output controller
Newsgroups: 
lugnet.robotics
Date: 
Fri, 26 Mar 1999 16:30:48 GMT
Original-From: 
alex wetmore <alex@*stopspam*phred.org>
Viewed: 
1007 times
  
On Fri, 26 Mar 1999, Lou Sortman wrote:
Joel Shafer wrote:

What about a real time circuit that routed the output power to one of eight
output ports depending on the PWM.  That way it only takes one output port
on the RCX and up to three (out of 24) motors could be running at the same
time.

And where are you getting motor drive power from?  I assume you want the selected
motor to run at full power, not at 1/8, 1/4, etc.  I'm afraid you're still stuck
consuming the extra output for power unless you use a separate power source.

With a seperate battery box (from 8735 for instance) you could power the
output full time.  In this case you'd probably want to map it to something
like this:
off - off
1 - output 1 fwd
2 - output 1 rev
3 - output 2 fwd
4 - output 2 rev
5 - output 3 fwd
6 - output 3 rev
full - output 4 fwd

(if there is a 7 then you could get 4 outputs in fwd and reverse).
You would get a max of 9 (or 12) outputs, but I think that would
be plenty for most RCX-type robots (I still really haven't had to
go beyond 3 outputs, but I've mostly built vehicles).


alex

--
Did you check the web site first?: http://www.crynwr.com/lego-robotics



Message has 2 Replies:
  Re: multi-device output controller
 
(...) 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 (...) (26 years ago, 26-Mar-99, to lugnet.robotics)
  Re: multi-device output controller
 
There is no need to waste PWM levels on reverse. You can set the RCX motor output to reverse speeds as well, giving you 7 outputs (fwd and rvs) instead of 3 1/2. You need a bridge rectifier anyway; you might as well exploit it to indicate direction. (...) (26 years ago, 26-Mar-99, to lugnet.robotics)

Message is in Reply To:
  Re: multi-device output controller
 
(...) And where are you getting motor drive power from? I assume you want the selected motor to run at full power, not at 1/8, 1/4, etc. I'm afraid you're still stuck consuming the extra output for power unless you use a separate power source. (26 years ago, 26-Mar-99, to lugnet.robotics)

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