Most of the electric fence chargers on the market are leagal only because they dont put out a constant voltage. They pulse the full charge for a v= ery short time every 1-2 seconds. Most states have outlawed the use of const= ant fence chargers. Also another thing you have to watch out for is fires. The largers ones can start fires when weeds touch the lines. I live on a large piece of property in N. VA and have been using electic fence chargers for a while now to protect my gardens from deer, coons an rabits. ----- Original Message ----- From: "Morgan Olsson" To: Sent: Sunday, August 04, 2002 8:03 PM Subject: Re: [EE]: Electric fence energy safety level > Peter L. Peres. wrote: > > >Ahh. You do direct shawarma from the sheep, right ? > > Yes http://130.225.180.126/JohannesHolmertz/shawarma > > Actually that article forgot to mention this new hunting+cooking techni= que > > >I don't know about sheep but people (like me) tend to react very badly > >from 20mJ up. > > Then i wont investigate my reaction to 6000mJ... > > How theese units are leagal i don=B4t understand... > > Problem is only a fraction goes through an eventual sheep touching the wire somewhere in this landscape... > Most energy go eaten by weeds, bushes, bad/moistcovered/missing insulators, wire loose and dropped on ground, ... > And thick fat water repelling fluffy fur is good insulator! > Combine that with rain wetting all weeds that hang over kilometers of w= ire and wet insulators... You really need to bash in quite some electrons if = you want a fraction of them to say hello to the sheep instead of taking a nic= e swim in the rain... > > >Is there > >some kind of voltage or current feedback from the output ? (look carefully > >it may be a current transformer implemented as PCB traces). > > Not in this one, but i believe a sister model do: > > High voltage part analysis: > > ##### =3D windings : > A =3D charge transformer secondary (Flyback) > B =3D Open air power inductor > C =3D Fence transformer primary > D =3D Fence transformer secondary > > D1 =3D fast 1 amp (actually 2 in series) > D2 =3D small switch diode > D3 =3D 6 amp 700V rectifier > SCR =3D 800V 300A pulse rated > C3 =3D 3 in series of 100n 660VAC rated. Across C3 there is also 5 ser= eis connected 10k 12W R and a small SCR with gate resistors triggering a Neon lamp just for indicating operation OK > > D1 ,-[2M2]-[2M2]--Charge voltage sense to firing controller > ,--->|---+-----+--------+----+--O NC1 > | | | | | ,------+--------+-O FENCE > | C1| | C2| | | | | > # 600V --- | 630V--- # # |C3 | > # 32=B5F --- | 1=B5F --- # # --- Open Spark Gap > # | | | # # --- about 6mm > # A +-->|-' | C # # D | | > | D2 | D3 | | | | | > +---|<---+ | | '------+--------+-O GROUND ROD > | | SCR B | | > +--[10R]-+--|<---#####--+----+-[180k]-[180k]-[Trimmer]-O NC2 > | | '-[33R]---firing from controller > | GND on controller > '-[3k3]-Sense to charging switcher controller (charge current) > > > Basically: C1 is charged by D1 and then dumped to fence by SCR. > Now, i think the capacitors C2 & C3 on both sides of the Fence transformer, (plus fence capacitance) toghether with the B inductor would make the voltage "overshoot" to much higher voltage than possible without= B. This inductance also would make it shoot back and the 32=B5F charge cap g= o negative if it was not for D3. Thus C! always get fully discharged, and = tha tis the only feedback voltage for the output. > > The only way i can think of that the controiller can evaluate the resul= t is by measuring time from firing until voltage hit zero. But i think tha= t would be very not exact as components tolerance is pretty high, and the behaviour is complex. > > But the two unconnected pin s NC1 and NC2 is across fence transformer, = and could provide a measurment of the result by i.e integrating the voltage during the pulse. However, thees pins seem intended for a doughter board controller. > > My analysis is that his unit is simply sending full charge pulses witho= ut regulation. (Before it broke...) > And that a regulator board was at least planned, maybe used in a sister model. > > (BTW the owner have now got anoter unit running, borreowe this weekend, and it seem too expensive to rebuild this if i charge by the hour anyway.= .. Have to reverse design as i can=B4t find a new controller IC. So i put i= t on hold for an unspecified while.) > > /Morgan > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu