garden gate sensor advice
 

I need advice for an off-the-shelf parts list, besides fine-guage wiring,
for doing the following:
We try to keep the dog contained in the backyard, but both gates are not
visible from the back door. What kind of wired system can I use that would
have two weatherproof sensors, one on each gate, and a small led-lighted
console by the inside of the back door, that would indicate the gate is
either open or closed?
Should this be battery powered, and what kind of wire and batteries should I
use? These are up to 120-foot runs, and the smaller the wire, e.g. telephone
wire, the better, for easy installation.
Thanks!

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Roger Taylor wrote:
I need advice for an off-the-shelf parts list, besides fine-guage wiring,
for doing the following:
We try to keep the dog contained in the backyard, but both gates are not
visible from the back door. What kind of wired system can I use that would
have two weatherproof sensors, one on each gate, and a small led-lighted
console by the inside of the back door, that would indicate the gate is
either open or closed?
Should this be battery powered, and what kind of wire and batteries should I
use? These are up to 120-foot runs, and the smaller the wire, e.g. telephone
wire, the better, for easy installation.
Thanks!



Hi,
I believe the standard-issue solution to this question is to place a
magnet on each gate (on the handle end of the gate, NOT the hinge end)
and a small reed-switch on the fence, arranged so they will almost touch
each other when the gate is closed. Run a pair of wires to the contacts
of the reed switch. When the gate is closed, the magnet closes the
switch; when the gate is open, the switch will also be open. This is
basically what security systems use to detect doors opening.

You should be able to use very small wires for this. Since LEDs use
little current, you should simply be able to put the power supply, the
reed switch, a current-limiting resistor, and the LED all in series. You
shouldn't need any transistor triggers or anything I don't think.

Also, this system has the advantage that a broken wire or burnt LED will
cause it to fail to the safer state: it's better to say the gate is open
when it's closed than to say it's closed when it's open (I would imagine).

Chris
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In article , Roger Taylor wrote:
I need advice for an off-the-shelf parts list, besides fine-guage wiring,
for doing the following:
We try to keep the dog contained in the backyard, but both gates are not
visible from the back door. What kind of wired system can I use that would
have two weatherproof sensors, one on each gate, and a small led-lighted
console by the inside of the back door, that would indicate the gate is
either open or closed?
Should this be battery powered, and what kind of wire and batteries should I
use? These are up to 120-foot runs, and the smaller the wire, e.g. telephone
wire, the better, for easy installation.
Thanks!

yeah, telephone wire would be fine, use the weatherproof stuff, not the
indoor stuff, as for sensors, it depends on the gates, but if you can get
reed switches to work they're real easy to waterproof as they have no
external moving parts, (reed switches are a type of sealed magnet-operated
switch, you attach the magnet to the gate and the switch to the gate post....
they only have a short range though (about 1/2" unless you get a biger magnet)

so if you're dealing with gates that don't close with that sort of
precision some other sort of sensor could be better

with the reed switches they have can often be wired to conduct in the
absense of the magnet (look for one with normally closed contacts) so
that the LED would light with the gate open

3V is enough to light the LED (use a 68 ohm resistor in series) so two D
size cells in series should run it for quite a while...

--

Bye.
Jasen