Hi all. Thanks in advance for any help you can give. Please note my
email address is invalid - this is to stop spam. Reply to gazman at
pobox dot com to email me directly.

Here's my problem :

My front gate is 150M from the house and I will have an intercom and
system to open the gates, turn on the lights, etc etc.

I ran two Cat 5E cables (total 16 conductors) underground. Somehow one
of the cables has been cut, so I have only 8 conductors left. The
intercom requires 5 of these, so I have just 3 conductors to control
the gates, lights, fountain etc as well as send a signal back to the
house to indicate what position the gate is in.

So I need a circuit that can send a coded signal down the wire, which
is decoded at the other end to open or close a relay.

My suggestion is this : At the house, each of 6 control buttons sends
a signal down the wire at a unique frequency. At the gate a circuit
detects the signal, and according to its frequency, toggles one of 6
relays. That way, multiple relays can be activated using just a pair
of wires.

It would NEVER occur that two control buttons are pressed at the same
time.

There are other ways of coding the signal (pulse count for example)
and I have used frequency just as an example.

Does anybody know where I can find a circuit to do this sort of thing?
I have searched the web without success.

Thanks in advance.

Gaz

Gaz Man writes:
...so I have just 3 conductors to control
the gates, lights, fountain etc as well as send a signal back to the
house to indicate what position the gate is in.

So I need a circuit that can send a coded signal down the wire, which
is decoded at the other end to open or close a relay.
....
There are other ways of coding the signal (pulse count for example)
and I have used frequency just as an example.

Does anybody know where I can find a circuit to do this sort of thing?
I have searched the web without success.

IF you could still find an old dumb uart chip, one that didn't need
all the programming registers configured, that just woke up and
presented the last received serial byte on the 8 output lines...
THEN you could use one line for the clock and a second line for the
serial data. You are beyond the specificaitons for RS232 to go that
far but it might work anyway. Or you could just use beefier drivers.
I remember a little circuit that used a 74H00 nand gate that was
claimed to drive signals hundreds of meters.

So, the circuit for that is just to find a really really old uart,
maybe on Ebay, that is so dumb that all it knows how to do is work.
Clock in, data in, and you just keep sending the same byte to it
with the appropriate bits set. To avoid needing crystals and all
the mess of getting the frequency just right you could use the
sending uart's clock signal sent down the second wire. Usually
this clock signal is something like 16x the actual data rate and
you feed the same clock to both uarts. The actual clock rate is
probably a don't-care in your situation, just don't have it jumping
around. You might be able to configure a PC to deliver the clock
out, I don't remember whether there is any way to get that out of
new uart's today or not.

"Gaz Man" wrote in message

Hi all. Thanks in advance for any help you can give. Please note my
email address is invalid - this is to stop spam. Reply to gazman at
pobox dot com to email me directly.

Here's my problem :

My front gate is 150M from the house and I will have an intercom and
system to open the gates, turn on the lights, etc etc.

I ran two Cat 5E cables (total 16 conductors) underground. Somehow one
of the cables has been cut, so I have only 8 conductors left. The
intercom requires 5 of these, so I have just 3 conductors to control
the gates, lights, fountain etc as well as send a signal back to the
house to indicate what position the gate is in.

So I need a circuit that can send a coded signal down the wire, which
is decoded at the other end to open or close a relay.

My suggestion is this : At the house, each of 6 control buttons sends
a signal down the wire at a unique frequency. At the gate a circuit
detects the signal, and according to its frequency, toggles one of 6
relays. That way, multiple relays can be activated using just a pair
of wires.

It would NEVER occur that two control buttons are pressed at the same
time.

There are other ways of coding the signal (pulse count for example)
and I have used frequency just as an example.

Does anybody know where I can find a circuit to do this sort of thing?
I have searched the web without success.

Use a twisted pair as an RS485 link and have a microprocessor at each
end - ultimate flexibility.

--

Brian Gregory (In the UK).

To email me remove the letter vee.

On Mon, 26 Apr 2004 19:30:20 +1000, Gaz Man wrote:

Hi all. Thanks in advance for any help you can give. Please note my email
address is invalid - this is to stop spam. Reply to gazman at pobox dot
com to email me directly.

Here's my problem :

My front gate is 150M from the house and I will have an intercom and
system to open the gates, turn on the lights, etc etc.

I ran two Cat 5E cables (total 16 conductors) underground. Somehow one of
the cables has been cut, so I have only 8 conductors left. The intercom
requires 5 of these, so I have just 3 conductors to control the gates,
lights, fountain etc as well as send a signal back to the house to
indicate what position the gate is in.



Isn't it actually worse? How are you going to power the decoding
electronics at the remote end? Can you get another supply or are you stuck
with ground, supply & a single data line?

Having said that, I'm sure it can be done. I've seen an alarm chip that
used the supply line for bi-directional data transfer on a 2-wire system.
Only a couple of i/o each way though IIRC.

7-segment LED display drivers look good for remote output shift registers
- with about 32 outputs!

--
Cheers...
Mick
Gave up on viruses & trojans - moved to Linux... :-)
Nascom & Gemini info at http://www.nascom.info

Gaz Man wrote in message . ..
Hi all. Thanks in advance for any help you can give. Please note my
email address is invalid - this is to stop spam. Reply to gazman at
pobox dot com to email me directly.

Here's my problem :

My front gate is 150M from the house and I will have an intercom and
system to open the gates, turn on the lights, etc etc.

I ran two Cat 5E cables (total 16 conductors) underground. Somehow one
of the cables has been cut, so I have only 8 conductors left. The
intercom requires 5 of these, so I have just 3 conductors to control
the gates, lights, fountain etc as well as send a signal back to the
house to indicate what position the gate is in.

So I need a circuit that can send a coded signal down the wire, which
is decoded at the other end to open or close a relay.

My suggestion is this : At the house, each of 6 control buttons sends
a signal down the wire at a unique frequency. At the gate a circuit
detects the signal, and according to its frequency, toggles one of 6
relays. That way, multiple relays can be activated using just a pair
of wires.

It would NEVER occur that two control buttons are pressed at the same
time.

There are other ways of coding the signal (pulse count for example)
and I have used frequency just as an example.

Does anybody know where I can find a circuit to do this sort of thing?
I have searched the web without success.

Thanks in advance.

Gaz

If you have 6 distinct control signals, and only one can be sent at a
time, you could use the 3 conductors as a simple digital link. With 3
bits, there are 8 possible combinations. If you use a 3-8 decoder (a
readily available IC), you can tie 6 of the outputs to relays (be sure
the relay doesn't exceed the decoder's max output current) and use one
of the remaining two combinations as a "no action" signal. At the
house end, you could use a priority-encoder IC (such as the 74F148) to
generate these signals.

It would also be possible to use tone encoding as you described, and
this would have the advantage that you could press more than one
button at a time. Simply connect 6 tone generators (maybe built from
555/556 timer IC's) to a summing amplifier at the input end, and 6
tone decoders at the output. This would, however, be much more
difficult than the digital method.

Gaz Man wrote in message . ..
Hi all. Thanks in advance for any help you can give. Please note my
email address is invalid - this is to stop spam. Reply to gazman at
pobox dot com to email me directly.

Here's my problem :

My front gate is 150M from the house and I will have an intercom and
system to open the gates, turn on the lights, etc etc.

I ran two Cat 5E cables (total 16 conductors) underground. Somehow one
of the cables has been cut, so I have only 8 conductors left. The
intercom requires 5 of these, so I have just 3 conductors to control
the gates, lights, fountain etc as well as send a signal back to the
house to indicate what position the gate is in.

So I need a circuit that can send a coded signal down the wire, which
is decoded at the other end to open or close a relay.

My suggestion is this : At the house, each of 6 control buttons sends
a signal down the wire at a unique frequency. At the gate a circuit
detects the signal, and according to its frequency, toggles one of 6
relays. That way, multiple relays can be activated using just a pair
of wires.

It would NEVER occur that two control buttons are pressed at the same
time.

There are other ways of coding the signal (pulse count for example)
and I have used frequency just as an example.

Does anybody know where I can find a circuit to do this sort of thing?
I have searched the web without success.

Thanks in advance.

Gaz


If you have 3 conductors (I'm assuming you can steal power and ground
from the intercom), I'd go with a digital link. Connect a 3-8 decoder
to the 3 signal lines and the 6 relays (be sure the coils don't draw
more current than the decoder can supply--otherwise, a transistor or
op amp will serve as a buffer), and drive the line with an 8-3
priority encoder (like the 74F148) whose inputs are connected to the 6
buttons. You could use an 8-input NOR gate to activate an unused input
when all buttons are open.

"Gaz Man" wrote in message
...
Hi all. Thanks in advance for any help you can give. Please note my
email address is invalid - this is to stop spam. Reply to gazman at
pobox dot com to email me directly.

Here's my problem :

My front gate is 150M from the house and I will have an intercom and
system to open the gates, turn on the lights, etc etc.

I ran two Cat 5E cables (total 16 conductors) underground. Somehow one
of the cables has been cut, so I have only 8 conductors left. The
intercom requires 5 of these, so I have just 3 conductors to control
the gates, lights, fountain etc as well as send a signal back to the
house to indicate what position the gate is in.

So I need a circuit that can send a coded signal down the wire, which
is decoded at the other end to open or close a relay.

Silly question, but, you did run these inside of a conduit, didn't you?

Why not just pull a new cable?

Rs232 will probalby still work....just drop the baud rate to 1200 or so....
If your cables run along with your cables...you might have hooped yourself
with the noise you'll get on your sig cables....but hey, thats what RC
filters are for!


"Don Taylor" wrote in message
...
Gaz Man writes:
...so I have just 3 conductors to control
the gates, lights, fountain etc as well as send a signal back to the
house to indicate what position the gate is in.

So I need a circuit that can send a coded signal down the wire, which
is decoded at the other end to open or close a relay.
...
There are other ways of coding the signal (pulse count for example)
and I have used frequency just as an example.

Does anybody know where I can find a circuit to do this sort of thing?
I have searched the web without success.

IF you could still find an old dumb uart chip, one that didn't need
all the programming registers configured, that just woke up and
presented the last received serial byte on the 8 output lines...
THEN you could use one line for the clock and a second line for the
serial data. You are beyond the specificaitons for RS232 to go that
far but it might work anyway. Or you could just use beefier drivers.
I remember a little circuit that used a 74H00 nand gate that was
claimed to drive signals hundreds of meters.

So, the circuit for that is just to find a really really old uart,
maybe on Ebay, that is so dumb that all it knows how to do is work.
Clock in, data in, and you just keep sending the same byte to it
with the appropriate bits set. To avoid needing crystals and all
the mess of getting the frequency just right you could use the
sending uart's clock signal sent down the second wire. Usually
this clock signal is something like 16x the actual data rate and
you feed the same clock to both uarts. The actual clock rate is
probably a don't-care in your situation, just don't have it jumping
around. You might be able to configure a PC to deliver the clock
out, I don't remember whether there is any way to get that out of
new uart's today or not.

What powers your intercom? something you can steal power off of?
a microprocessor will run a while on a battery. You'll probably need a
higher voltage to run your relays and lights....plenty of ways to go about
this.

I like the microprocessor idea. www.parallax.com sells good kits for people
that don't need to know much. Great support and plenty of documentation!


"Form@C" wrote in message
news
On Mon, 26 Apr 2004 19:30:20 +1000, Gaz Man wrote:

Hi all. Thanks in advance for any help you can give. Please note my
email
address is invalid - this is to stop spam. Reply to gazman at pobox dot
com to email me directly.

Here's my problem :

My front gate is 150M from the house and I will have an intercom and
system to open the gates, turn on the lights, etc etc.

I ran two Cat 5E cables (total 16 conductors) underground. Somehow one
of
the cables has been cut, so I have only 8 conductors left. The intercom
requires 5 of these, so I have just 3 conductors to control the gates,
lights, fountain etc as well as send a signal back to the house to
indicate what position the gate is in.



Isn't it actually worse? How are you going to power the decoding
electronics at the remote end? Can you get another supply or are you stuck
with ground, supply & a single data line?

Having said that, I'm sure it can be done. I've seen an alarm chip that
used the supply line for bi-directional data transfer on a 2-wire system.
Only a couple of i/o each way though IIRC.

7-segment LED display drivers look good for remote output shift registers
- with about 32 outputs!

--
Cheers...
Mick
Gave up on viruses & trojans - moved to Linux... :-)
Nascom & Gemini info at http://www.nascom.info