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Date:      Thu, 29 Jun 2000 18:23:51 -0600 (MDT)
From:      "Forrest W. Christian" <forrestc@imach.com>
To:        Brandon Fosdick <bfoz@glue.umd.edu>
Cc:        freebsd-small@FreeBSD.ORG
Subject:   Re: OT: Embedded system suggestions
Message-ID:  <Pine.BSF.4.21.0006291808110.3926-100000@workhorse.iMach.com>
In-Reply-To: <395BE8B2.176EE0F3@glue.umd.edu>

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On Thu, 29 Jun 2000, Brandon Fosdick wrote:

> I was thinking about 3, 48 line digital input boards (don't know where to get
> those) and maybe some digital output boards that can drive relays. Where do I
> find this stuff? Does it even exist? What kind of processors do I use? What kind
> of power supply do these systems need?

If you're really clued, you can build these yourself.  I personally would
probably do something with some PIC processors on a serial port or
alternatively something slightly less complicated
(programming-wise) parallel port or ISA based.   

(Or if you'd like someone to build it for you or need more details send me
e-mail off-list)

Regardless, this exists commercially and is generally rather expensive.  

I would be looking in the latest issue of Nuts and Volts and/or Processor
if I was to buy.

Just Curious, is there a reason you are going the relay route as opposed
to the X10 route?

 
> I found a 216 line DIO board at www.icsadvent.com but it can't drive inductive
> loads (i.e.. the relays). If all else fails I'll use this board and just make a
> separate board with diodes and resistors for the relays.

Inductive load = motor,  Inductive load != relay.   You will want to put a
diode across the coil of the relay to nail any spikes.   1N914's seem to
work although seem a little light at times, 1n400x's are probably better
to handle the spike but are slower.   If given the choice, I'd probably
use the 914's (available and any radio shack).

- Forrest W. Christian (forrestc@imach.com) AC7DE
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iMach, Ltd., P.O. Box 5749, Helena, MT 59604      http://www.imach.com
Solutions for your high-tech problems.                  (406)-442-6648
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