is the gate open or closed

[MicroRem]

I believe I saw a thread similar to this earlier but failed in locating it. My driveway gate is about 800 feet from my house. Anyone think of a kit or simple rf circuit built or not, to tell me whether the gate is open or closed? The sensor will probably be a magnet or reed switch or something similar. If I had multiple channels I could probably determine if the mail had arrived also. Anyway, thanks in advance for your input.

Tom

[gerty]

Is it a powered gate? If so, probably the cheapest/easiest would be X10.
You can put a X-10 transmitter at the gate and plug the reciever in at the house.

[sofaspud]

Go to Ramsey and take a look at their transmitters, receivers, and information concerning non-licensed broadcasting.

[MicroRem]

Gerty, no, the gate is not powered. Maybe will be at some point but no access to ac lines.

Tom

[Sambuchi]

I've used these in the past and posted these links recently.

http://www.sparkfun.com/commerce/produc ... ts_id=8947

http://www.sparkfun.com/commerce/produc ... ts_id=8945

500 ft thou

[jwax]

Do you have a line of sight to the gate? (I'm thinking maybe an optical solution here)
If you went with an RF solution, what do you have for power at the gate? Is solar available?

[kheston]

Anything with a transmitter would be relatively power-hungry. If my math is right, the device sambuchi linked to draws ~60mah, so a 9v battery would only power it for 10 hours. You would therefore need something more substantial and plan to have some charging mechanism in place (solar or two batteries to swap with a wall-wart). You could also have it transmit only when the gate was open, but then you'd always wonder if your batteries were dead. Have you considered the low-tech approach?

How long would it take to bury 800ft lawn-sprinkler wire using a trencher? It might be worth the peace of mind.

[jwax]

No need to transmit continously. Only needs to send a change-of-state signal. The receiver would simply toggle between OPEN and CLOSED indication whenever the transmitter changed from open to closed status.
These guys make any number of channels, range, or mode- momentary/toggle/latch transmitters and receivers:
http://stores.ebay.com/e-MadeinCHN?_rdc=1

[jollyrgr]

You may consider using something like a home security system that uses wireless sensors. There are many sensors and if you use something like a GE Concord (either Express for basic, or Concord 4 for "professional") it will have built-in wireless receivers. The sensor types are many. Some of the door sensors can also have external contacts connected to them. The range of some of the sensors can be as much as 1000 feet (depending on environment).

Here is the sensor I was considering:

http://www.safemart.com/GE-Security-Wir ... -319-5.htm

Check pricing CAREFULLY! The sensors "CAN" work up to 1000 feet per the manual. If you wish you could install the security system for your house and add the gate as an extra input (I think they allow up to 96 with the Concord 4). On the keypad you hit STATUS and it will tell you what doors and windows are open. You can program the full name for each sensor (Front Door, Sliding door, Gate, etc.).

I cannot say 100% this would work but it is an idea. You'd have to house the sensor linked above in a water tight case. The batteries last 8 to 10 years in a normal environment. I don't know how cold it gets in your area but in winter this may not work.

[Externet]

Hi.
It would be neat to attach a mirror to the gate in such way that a laser pointer very fixed at a high or convenient place with gate visual bounces back to a determined wall or target.
Apply power briefly. Dot back ? yes, it is closed. No dot return ? Well, take a walk to close it. Batteries in a laser pointer will last a couple of years with such duty cycle.

Same medicine for the mailbox, another pointer. Its mirror to flip-flop, its position to be reset after picking mail.

Miguel

[CeaSaR]

I was going to suggest a twin pair wire buried to the gate along with a NC reed switch and magnet. All
the power would be back at the house. The line would just be for the switch. All you'd need is continuity.

Then I thought about a setup where you have the magnet and same reed switch turn on a transmitter
when the gate opens. The transmitter would ping once every 10-30 seconds (or so) triggering a timer
back at the house. The timer would stay high as long as a ping is received. Once the gate is closed,
pings stop and indicator extinguishes at time-out. Advantage: low duty cycle saves battery life and if
you don't see the indicator and go to leave via gate, you can change the batteries then. Of course
button cells and 9v's are out for longevity in this environ. I'd suggest C's or D's for power. Anyone have
any thoughts or designs along this line?

CeaSaR

[sghioto]

CeaSaR said:

I was going to suggest a twin pair wire buried to the gate along with a NC reed switch and magnet

Then I thought about a setup where you have the magnet and same reed switch turn on a transmitter
when the gate opens.

If practical maybe a combination of the two.You could move the transmitter closer to the house connected to the gate switch by a simple pair for better range depending on transmitter device selected.

Steve G.

[jwax]

They actually sell driveway alert monitors, which could be slightly modified to indicate gate position, or are you keen on building your own?

[MicroRem]

Lots of great stuff to think about here. I will try to answer most of the questions asked so far. I could bury twisted pair but would prefer not to. Its about 800 feet and I'm really trying to avoid actual work. I could easy power a transmitter with a gel cell and solar, and may go that route. The gate is a "field fence and therefor moves a bit in the wind so I suspect using a laser is out due to the alignments issues, alsom we get quite a bit of morning fog and that would be a problem also. I going to look more closely at the links provided and see what I come up with. I'll keep ya'll posted, thanks for the great response from everyone.

regards

Tom

[CeaSaR]

Ah, a field gate. Single or double? Attached to a wire fence? If so, does the fence run to/close to your
house/shop/barn? If so, is the fence isolated from the ground?

If you can answer yes to the yes or no questions, you have a long run high impedance conduit to use
as a signal path from any "switch" at the gate to your choice of indicator location. A good earth ground
at each end and the fence becomes the signal wire. All you need then is a FET based high gain circuit
to detect the open/closed condition at the gate.

As for the gate, the style depends on how to handle it. Single gates are easiest to work with as they
normally are latched to a post. If you have the ability to do so, try mounting 1 or 2 of those heavy-duty
pickup magnets (~100 lb pull) so as to help stabilize the gate. You can find them at Harbor Frieght and
other stores/mailorders of that type. You could then mount the detector (switch, etc.) to the gate (or
post opposite the magnet) and when the gate is far enough away, the "switch" will open, sending the
signal down the "wire" (fence).

Double gates are a problem unto themselves. You'd need a way to "fix" one side of the gate (usually a pipe
set into the ground with a sliding pipe lock that goes into that pipe). You'd still need a way to detect the
open gate condition, either a switch or a way to read angular deflection. I'll leave that up to someone else
that would like to try.

Hope I gave you some possibilities.

CeaSaR