At 11:29 AM 5/31/2005 +0200, you wrote:
>Dear Spehro Pefhany,
>
>Thanks, I have looked at your circuit. Just want to clear up some confusion.
>
>According to the schematic there are a ground(0V track on the PCB) and a
>earth(close to the spark gap).

Yes, they are connected together, close to the where the fence loop return
connects.

>The transistor, 10K Resister, 10uF cap and TVS are all connected to the
>ground.

Yes.

>There must also be a short(thick) track from the TVS to the pad that will
>connect the ground to earth
>Do I understand this correctly?

Correct.


>So when the loop is fine there will be a approx 1mA current and the PIC
>input will be low.

High.

>When the loop gets broken there will be approx 0.23mA
>current. The Transistor base will see approx 2.3V

0.6V, because it's a BJT with ~250uA flowing into the base

>  and the PIC input will
>read High

Low.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


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