Newsgroups: comp.robotics
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From: jhurst@netcom.com (John Hurst)
Subject: Re: Getting 16 Relay outputs from a PC
Message-ID: <jhurstCM189u.DDv@netcom.com>
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References: <markdahlCLpMBt.495@netcom.com> <1994Feb25.165220.25960@osuunx.ucc.okstate.edu>
Distribution: usa
Date: Wed, 2 Mar 1994 10:10:41 GMT
Lines: 28

Gordon Couger (gcouger@olesun.okstate.edu) wrote:
: In article <markdahlCLpMBt.495@netcom.com>,
: Mark Dahlen <markdahl@netcom.com> wrote:
: >
: >I'm in great need for 16 or more Relay outputs from a PC running Qbasic.  
: >The use would be to control motors and lights for a little robot that I'm 
[deleted]
: Add a second parallel port and hook lines 2-9 to IR511 FET I would probably
: use opto-isolators between the parallel line and the gate of the 511 to
: keep switching noise out of the computer. Also a .01 ufd capictor needs
: to go from the gate to ground to keep the 511 from osilating. Also a 2 or
: 3K resistor to pull the gate to the desired start up state. WARNING on
: boot up the parallel port does some flopping around ususaly coming to
: on off on off ... in the end. This is not the same for all computers.
: Because of this you can get some strange behavior at boot up and in
: crashes.

You could try driving a 74xx154 1 of 16 decoder by using the lower
4 bits for an address, another bit for set/reset and another bit for strobe.
Using the extra 2 bits and additional logic you could control up to
64 relays! Add flip flops to the decoded outputs to use multiple relays
simultaneously. Use Gordon's suggestions to drive your relays with the
decoded outputs.  I don't know how easily you can manipulate this setup
with BASIC. If you are creative you can build a nice controller for
less than $40.00.

John Hurst
jhurst@netcom.com
