RE: Electronics decoding of outputs

["i.bird@xxxxxxx" <Ian@xxxxxxx>]

Hi Mick

The answer is yes and no.

I 'think' there are 4 to 16 decoder chips - there are cirtainly 3 to 8
ones. I don't know without looking in the catalogues.

And now the BUT(s)

Using a decoder only you will only be able to change the state of one relay
at any given time if you have 16. Also with relays, if you remove the
switching current the relay will turn off. This means you will need some
type of flip flop which changes state with a pulse to hold the relay in its
given position. This now presents you with a state question, i.e. is it on
or off? There is also the question of what are you trying to do - assuming
these relays controlling the 4 lines swich at normal speeds you will be
sending all sorts of combinations down the decoder as you get to your final
state. You probably stand to have a load of very confused relays. The fix
would be to have a three to 8 decoder and then a 'switch' or 'do it' line
from the 4th output i.e. set up your address and then trigger it. Lots of
fun challenges like that.

I have been looking at this recently and you may be better off building a
PIC controlled board (like my relay board when it gets to production). This
would give you serial (or 485) control - your choice. If you want to know
more on this I will expand in another mail. Connect two together under
RS485 and you have 16 relays with status feedback!!

Ian B



Original Message:
-----------------
From: Mick Furlong hiltoneltd@xxxxxxx
Date: Fri, 7 Jun 2002 15:55:23 +0100
To: ukha_d@xxxxxxx
Subject: [ukha_d] Electronics decoding of outputs


Ok the same Linux box mentioned in my previous email has 4 outputs which
are
relay based potential-free switch contacts. These are rated 1.5A at 230 V
AC
and 2A at 30VDC.

What I would like to do is to decode these outputs giving me 
additional
states (something similar to how frank is doing the HV/IR stuff I guess)
if
my math holds up I should be able to control 16 relays using combinations
of
the 4 signals.

Is it as simple as using a set of logic gates to do this?

Is there a solution on a chip ?

Any other help?

btw I am VERY rusty with my electronics....23 years rusty ....so go easy
on
me ;)

Thanks
Mick



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