Electric fence?

I was interested in monitoring the electric fences on our farm to make sure they haven't shorted out, but am unsure how to isolate the high voltage pulse from the arduino.

All I would want to do is monitor for pulse, if no pulse is received within 30 second period send alarm to house.

Not sure how high the voltage is, it hurts when you touch it! but they are about one second apart.

Is this a job for a opto isolator???

yikes! Arent electrical fences running on several thousand volts? I guess that this connected to the Analog Pins wont work ;0)
Well, i am not sure... but wouldnt a fence induce a magnetic field that could be measured by a hall sensor (Those ARE these strange magnetic sensors, right?)?

Most likely some kind of resistive voltage divider driving a optoisolator could probably be designed. The software side should be pretty simple, just use millis() to capture the time from the last pulse and if not updated from a new pulse, time-out and issue an alarm.

Lefty

Some sort of capacitive pickup. Try seeing what you get out of a piece of wire parallel and about an inch away from the wire. This could feed some sort of voltage divider with a 5.1V zener diode clamp. This should output a square wave analog of what's on the wire.

Some sort of inductive pickup. 2 inch diameter coil, try a few turns coaxial to the wire. It will be an edge detector, producing a pulse when the voltage turns on and a pulse when it turns off (magnetic field build and collapse).

I'm assuming that this electric fence is pulsed DC in all this. And the pickup mechanism will have to be well insulated, kept from absorbing water and away from where your inmates can do physical damage.

(Or really rube goldberg, get one of those Neon fence testers and have it trigger a phototransistor. There's your HV optoisolator!)

Hmmm all great answers thankyou, I now get the impression its not a simple thing to do, but i will try, I can see myself getting zapped a couple times while experimenting.

some interesting answerers so far, but I'm going to take it a little more simplistic.......Arduino EMF detector.

Brilliant n00b, I'm joining your fan club!!! well actually I'll test it on the fence first but I cant see why it would not work.

There is nothing in that circuit that will protect the Arduino input pin from damage due to overvoltage. I suggest you put a 5.1 volt zener diode across the analog input pin and ground.

There is nothing in that circuit that will protect the Arduino input pin from damage due to overvoltage.

The current received from the EM field would be so low that I think the internal pin clamping protection diodes would handle that hazard. You would have to use two back to back connected zener diodes anyway as there is no rectification of the sensed EM signal so either +/- voltages could be present.

Lefty

Brilliant n00b, I'm joining your fan club!!! well actually I'll test it on the fence first but I cant see why it would not work.

:smiley: so this is what it feels like giving back to the community.....I like it!

Keep us posted!