NNTP-Posting-Date: Sun, 15 Dec 2002 14:31:56 -0600
From: firstname.lastname@example.org (John Fields)
Subject: Re: Digital circuit help needed
Date: Sun, 15 Dec 2002 20:17:04 GMT
Organization: Austin Instruments, Inc.
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On Sun, 15 Dec 2002 19:49:29 GMT, Fred Bloggs
>You must go to an addressable register setup.
_Must?_ That's only one of a myriad of choices available and your
way is flawed. Notice, from your sequence of events, that prior to
making a new parallel selection all the relays must first be
de-energized and then the new pattern applied. This precludes the
possibility of going from one pattern to the next without the
intervening "off" state. From the OP's post, ISTM that he'd like to
be able to hop from one pattern to the next without having to go
through the "off" state.
All of Spehro's suggestions will allow the circuit to be implemented
"Two 8 bit serial in parallel out SRs with output latches. 1 data
line, 2 clocks (expandable indefinitely, and you get 16 lines for
same complexity as 12 with this setup) Eg. 74HC595. This methiod is
nice if you have hardware SPI available, and is easily
being my favorite and what I use all the time.
>The sequence of events to make a new 12-relay subset selection is:
>1) Pull RELAY CTL high to disable all outputs- note your Darlington
>inputs must have pulldowns to GND- but not draw too much current from
>the HCT Q-outputs- like 10K ohms.
>2) Put the 4-bit relay select pattern, SEL DATA, and addrs, REG SEL
>ADDRS, for appropriate register on inputs;
>3) Strobe the DATA CLOCK input high to load data.
>4) Repeat steps 2&3 for the remaining registers.
>5) Pull RELAY CTL low to activate relays or high to turn all off.
Professional circuit designer