Small electricity problem to solve!

[Forhorse]

Here, after months of testing the high voltage part, to be sure that it will not burn after a few days, I took the time to finalize my assembly.

Here is a first diagram functional aspects a very basic little fence alarm. It's not just an idea but a fitting that works (I tested it)


No sending of sms or anything hi-tech with this first scheme. Just a relay that sticks when there is no more impulse on the fence.
The components could not be more current and are found almost everywhere (the most difficult to find must be the power resistors on the high voltage part)

Grelinette, if you're interested I can make you a working prototype with a box, etc ... If necessary, contact me by mp.

[dedeleco]

Very good !!
But since these are high voltage pulses we can use capacitors!
In alternating or pulses, capacitors can be used as a voltage divider, with less dissipation.
High voltage HV resistors can be replaced by capacities calculated for the same current, roughly the value of the capacity of 200nF divided by the ratio of the voltages, that of the fence (5000V?) Over that of La1 in protection (what value, 10 to 40V ??) or about 500 times lower therefore a capacity of 0,4nF = 400pF by putting some capacities in series less difficult to find.
For example, a dozen 4700pF 500V capacities in series at € 0,3

conrad.fr/cond_ceram_47nf_500v_z5upas_5mm_a_48674_49083_841522_123217

We must be able to reduce the 220nF and put very low capacitances, simple of a few pF, made by hand with copper sheets and insulation.

But if lightning falls very close, 1 or 2 blows per Km2 and per year, I am not convinced of the resistance of La1 and the rest, given my experience of lightning strikes over 40 years and still only on houses (alarms , VMC, and direct love at first sight which set fire to, burned the meter and circuit breaker EDF, the fridge, the heat pump, etc ... but not the TV, nor the computer !!!).
Varistors increase the indirect lightning resistance, for my alarms and VMC.
An inductive link (thin wire in coil with widely spaced turns) before varistor or La1 protects from lightning quite a lot because lightning is very fast and badly crosses inductive zones with low capacities, even a few turns, the million volts of the lightning is greatly reduced !!
Finally this is my explanation of the survival of my laptop and my TV, at the end of long twisted wires, while lightning was fierce on large metallic masses like my fridge or the cap with its tubes, by melting and setting it on fire !!
My surviving laptop power outlet was disconnected by lightning, proof that it saw 1 million volts pass, a microsecond !!

[chatelot16]

theft from an electric fence post becomes a calamity

I have a project above based on gsm

I tried with inexpensive phones which have a connector to use them as a modem: the problem is that they are all different and never available for very long ...

I prefer to don a telit gsm module for sale at lextronic: it is a little bit more expensive than a 20euro phone but it is well documented and easier

you don't necessarily have to pay a subscription every month: you can be content with a mobile card, paying a card every 6 months so that it receives the calls: just call the fence for what answer if it is OK

in case of theft the module will contain a reload card number to be able to charge credit and call up a whole list of numbers

of course it will be necessary that the gsm module is integrated into a solid enclosure, so that the thief takes the whole: if the anti-theft system is in a separate case the thief will break everything

by the way I solve another problem: the fence posts are always too small: you can't put a big battery in it: you would have to buy small special batteries ... while it works very well with very large tractor batteries , a little tired who no longer start the tractor ...

the heavy fence post is heavy will complicate the thief's task a little

the photovoltaic panel is an idea, but when the theft problem arises it is better to continue to carry batteries

[chatelot16]

to measure the tension on the wire no worries: I measure on the primary of the transformer which is in the fence post

the primary tension is largely different if the secondary goes up to normal tension or if the wire is short circuited

moreover with my preferred scheme if the wire is not short-circuited a good part of the energy of the pulse is returned to the capacitor, available for the next stroke ...