Electronics 2000

Hi all,

I'm looking for a simple way to build my own 12V-powered electric fencer circuit. I've Googled left, right and centre but can't find anything useful. A while back I opened up a dead one (I threw it away) and the circuit inside seemed pretty simple, but the units on sale are around £100! Why are they so expensive?

It seems like I need a large capacitor to store charge, then a timer system to dump the charge in a surge through a step-up transformer to provide a brief, kilovolt-order pulse for the output every 1.5 seconds or so.

I did A-level physics, but have no specific electronics qualifications, so please be patient!

Thanks in advance,

Andrew

A very simple solution would be to
use an old car(circa pre 1980) ignition circuit, consisting of a high voltage coil and distributor.

You could time the pulses of the high output by simply connecting a motor to the distributor which would open and close the contact points in the distributor depending on the speed of the motor.

Thanks, Biffo, that would definitely work but might it be a little power-hungry? Also, I'm looking for a pulse every 1.3 seconds or so, so I might have to grind down three lobes of the distributor cam to reduce the frequency of pulses, or the fence might give out a taser-like shock! I was looking for a solid-state solution, and from a discussion on another electronics forum I found this:

http://www.stegoweb.net/pages/electric-fence.htm

I have ordered the parts, but the chap on the other forum is extremely concerned about safety, so I've promised to test it thoroughly with my scope before using it. I'll report back.