Subject:
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RE: Motor output multiplexing
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 7 Jan 2000 20:52:03 GMT
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Viewed:
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757 times
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I have built two prototypes of an output demux. I take the three outputs
as BCD, run each through a diode bridge, filter cap, and current limiting
resistor to tickle the base of an NPN transistor. Use the output of the
three transistors to drive a 74HCT138 demux. Use the 8 TTL sinking outputs
(20 mA) to drive whatever you want. I've driven bigger transistors, and
also some nifty Aromat relays.
There are some real limitations.....You give up directional control, or you
have to use two outputs. Ditto speed control. Only one demuxed output can
be on at a time. One will always be on.
That said, there are some real advantages. You can (actually you have to)
use an external power source for the motors. You can drive bigger loads
like solenoid valves.
I fit mine into a RCX battery case, with it's own 9 volt battery, so the
demux box has 8 outputs, and 9 vdc raw, and 5 vdc regulated. Frankly, I
don't use it much, but it was a fun project.
I can send the schematic as a bitmap, .dxf, or Autocad drawing if anyone is
interested. It's an easy project.
Jeff
jeffrey.hazen@northmill.net
-----Original Message-----
From: Douglas McIntyre [SMTP:lego-robotics@crynwr.com]
Sent: Friday, January 07, 2000 2:56 AM
To: lugnet.robotics@lugnet.com
Subject: Re: Motor output multiplexing
Has anyone come up with an electronic solution to the problem of only
having
3 out ports?
It seems it would be possible to control many more motors if some sort of a
multiplexor was constructed,
maybe the motors could use their own power supplies and use output ports as
inputs to the multiplexor.
I just joined the list so sorry if this topic has been discussed :)
Also, has anyone developed a sensor using a digital compass?
Doug McIntyre
Developer of MPOGD
http://www.mpogd.com
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