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Subject: 
Re : stuff (Big motor control)
Newsgroups: 
lugnet.robotics
Date: 
Sat, 16 Oct 1999 21:59:24 GMT
Original-From: 
Stephen Unwin <stephen@elmsfarm.demon.coSPAMLESS.uk>
Viewed: 
583 times
  
The following circuit should provide directional control
of a DC motor using two SPDT (Single Pole Double Throw) relays
and four diodes, but may not act quick enough for a PWM drive.



   .--------O---------------------------.
   |        |                           |
   |        |                           O-------------.
   |        |                           |             |
   |      \----/                      \----/      .-------.
   |       \  /                        \  /       |Relay 1|
   |      __\/__                      __\/__      '-------'
   O        |                           |             |
            |                           O-------------'
  RCX       |                           |
Output     |                           |
            O-------------.             |
   O        |             |             |
   |      --/\--      .-------.       --/\--
   |       /  \       |Relay 2|        /  \
   |      /----\      '-------'       /----\
   |        |             |             |
   |        O-------------'             |
   |        |                           |
   '--------O---------------------------'


      V+
      |
      O-----------------.
      |                 |
      O|                O|
nc 1   |                 | nc 2
      O|                O|
      |       ___       |
      |    .-/   \-.    |
      O----| | M | |----O
      |    '-\___/-'    |
      |                 |
      O  |              O  |
no 1     |                 | no 2
      O  |              O  |
      |                 |
      O-----------------'
      |
      GND


I have just come back from the pub where I've been thinking about this.
I haven't looked at the output signals on an oscilloscope yet, but I think
the following may work.
Assuming you are driving a more substantial motor than a LEGO one, you will
have a separate power source with which to power any circuitry.
You can have two op-amps set up as comparator circuits with a small (+0.5v)
bias on the positive inputs. On one op-amp the +input gets one side of the
RCX output and the -input gets the other side. This is reversed on the
second op-amp. The output of one these comparators goes to SET of an S/R
flip/flop and the other to the RESET. This will give a logic signal for the
direction on Q of the flip/flop and an inverse signal on Qbar.
Both signals from the comparators can also be NANDed to give a logic pulse
for PWM. These three signals can go into half of a L293D driver chip or
a stepper motor driver chip.
in1 = Q
in2 =Qbar
enable = NAND output.



     /////
    < .. >
       >
      -       stephen@elmsfarm.demon.co.uk



Message has 1 Reply:
  Control your Lego Mindstorms RCX across the internet using Microsoft NetMeeting
 
The WebRemote Device Controller allows you to control devices across a NetMeeting connection... If you have devices to control then you simply run the device controller, add the drivers for your devices and connect to NetMeeting to make the devices (...) (25 years ago, 17-Oct-99, to lugnet.robotics)

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