Subject: From: Date:

Re: [ECS] micro-redac and relays David Mccoll Thu, 24 Dec 1998 13:34:54 -0800

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Mark S.
First off you want to go into a digital input, not a relay output.

A couple preliminary things to check:

Is the Redac an  (8analog x 8digital x 8relay) or a (16d x 16r x 8a) or a
(16d  x 16a x 16r)
How old is the Redac ?
You should have screw in terminals on the board for the digital inputs. If
not then there may be 2 rows of 10 pins

As always there are more than one way to skin the cat but this one is best
done with this method:

You will need to 3 to 12 Volt plug-pak wall transformer which you will plug
into your receivers SWITCHED AC outlet. The low voltage end of the plug-pak
can be cut off and then connected through a resistor and fuse to the digital
input of the Redac.

The fuse will protect your computer system from meltdown should the worst
happen and the resistor keeps the current in the circuit to a minimum. This
becomes more important when you use higher voltage plug-paks, so if you use
a 5 Volt plug pak the loop current will be much lower than a 12 Volt
plug-pak. Also the plug-paks have a much higher no-load voltage for example
the 12 Volt paks often measure at 18 Volts.  A smaller plug-pak is
recommended and the current rating on the plug-pak could be anywhere from
50mA to 500mA the smaller the better. The resistor and fuse can be added
later, after you get the thing up and running, but don't leave it in service
without a fuse.

The fuse should be less than 1/2Amp. You can get 100mA fuses called
Picofuses at electronics supply shops. I personally use what is called a
poly-fuse rated at 100mA which is like a circuit breaker that can be reset
when you remove the power so you don't have to buy more fuses if you blow
one. Either way they are cheap insurance. Both kinds are physically the size
of a long-grain rice with axial or radial leads.

The value of the resistor can be calculated for a 10mA loop current with the
R=E/I formula. Or simply start with a 4.7k resistor, if it works keep it,
else try a 2.5k and work down. The larger the value, the lower the loop
current and the safer it is. I use a 4.7K resistor with a regulated 12 Volt
supply for all of my digital and it works fine.

Connection to the Redac may be different on your unit so you should be
certain and have a look at the docs that came with it. If they are on disk
fire me off  a copy and I will have a look. The digital inputs on my (16d x
16r x 8a) Redac are 2 banks of 10 position screw down terminals. 2 of the 10
terminals are the commons. One lead of the plug-pak goes to the common and
the fused lead goes to the digital input. If there are 2 connections for
each input then they are likely isolated from one another.

Create an item in your ECS config named as you like with a Type of
Digital-Input-C and the Station set to 0 if you have only 1 Redac. and the
input number.  I would suggest creating an item for ALL of your digital
inputs that way you can monitor them all at once in a Group  screen.

David McColl
dmccoll@intergate.bc.ca


-----Original Message-----
From: Mark Sekelsky <Mark@sekelsky.com>
To: ECS <ecs-list@netbloc.com>
Date: Thursday, December 24, 1998 9:06 AM
Subject: [ECS] micro-redac and relays


>I want to use a relay-c item but don't kow how to do this.  Here's what I
>want to do:  I want to be able to tell whether or not my receiver is on.  I
>have a relay that I can plug into the power outlet on the back of the
>receiver.  When the relay is open/closed I will know that the receiver is
>off/on.
>
>I assume that I want to run the wires from that relay (plugged into the
back
>of the receiver) to the relay posts on the micro-redac.  The redac has two
>rows of 8 posts each, numbered from 0 - 8.  What do I connect to?  Please
be
>gentle with me as I am a relay neophyte <g>.
>
>Hapy Holidays to al.
>
>Mark S
>
>

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