Hi, I'm wanting to put a hidden sensor on my farm gate to advise me when gate is opened and was thinking a sensor that could be fitted into a gate post or fencepost (drill hole, insert sensor, not easily spotted).
I have the wireless comms aspect sorted to buzz at house 200m away (this works fine) but am now unsure which of the myriad options for sensors would be best. I tried ultrasonic but sensor is large and was not terribly reliable. The gate is a simple chain over latch type latch so not really suited to a mechanical switch. I'm thinking laser or ultrasonic or perhaps IR switch. Anyone know of something suited to arudino which could be easily hidden in fencepost?
aarg:
This is a good time to ask about distances. At what minimum distance should it be "closed"? At what maximum distance should it be "open"?
Good questions, I should have been more specific.
Well there are two ways to do this:
Detect when a person or vehicle approaches the gate
Detect when the gate is opened - this is the preferred option I think.
The gate is a swinging farm gate (not sliding) and is about 3.5m wide, 1m high, steel tube frame with wire netting.
Any movement of the gate from closed to opened needs to be detected, ie even opening it 1 foot for a person to get through, or wide open for a vehicle.
RFID will not work with visitors? I'm not necessarily trying to keep people out, simply detect when they try to come in.
Hall effect/magnet: Presumably this will need equipment in both gate and post? How far apart can the two be and work reliably?
Thanks
I would first try mounting a snap-action microswitch (possibly with roller lever) at the gate hinge, with a cam of some sort on the moving part of the gate. They are rugged and extremely reliable.
Hi,
To sense the metal gate you need an inductive sensor, these come in a variety of shapes and sizes and are WEATHER PROOF.
You could hide the sensor in a fence post.
google
inductive sensor arduino
There are projects and YouTube clips to show you applications and principles.
Hi! If the goal it´s simply to know when the door is opened (and closed) a magnetic door sensor such as those used in alarm systems is a great tool: cheap, reliable, easy to install, no mechanical parts.. and cheap
Sample:
The sensor needs no power. You may read the status with any Arduino digital input.
An even easier solution will be to ground the hinge end. Then insulate the fixed portion of the latch. When the gate is fastened, the insulated latch is grounded, When the gate is opened, the insulated latch is not-grounded.
nzmuzzer:
Hall effect/magnet: Presumably this will need equipment in both gate and post? How far apart can the two be and work reliably?
The magnet doesn't have any electrical connections. It's just a magnetic slug. I asked you about distances and you never responded. I suppose a few centimeters would be the answer for Hall effect sensors. Shorter for the digital type (with built in on-off threshold).
