HV, Microprocessors, electric fences and tasers

[gwenhastings]

Hi all,
I have been looking into the idea of an electric fence whose HV waveform is generated by microprocessor attached to a drive transistor and sparkcoil...(yes I know that the coil is part of what determines and shapes the pulse also). A previous example could be found on the net here
http://hmin.tripod.com/als/andysm/docs/ ... cfence.pdf which used 2 x NE555 as the timing element for the HV pulses.
I also have been looking over http://www.google.com/patents/US6999295 ... &q&f=false which has the schematics of taser.com's x26 taser.. which shows considerably more sophistication in the HV section..

I also have a number of taser cartridges and I am curious as the the waveform needed to fire them.(door taser? window taser? taser wall??)

I have couple of old arduinos to burn that wont be missed...

any suggestions about protecting the arduino(s)(besides isolating the arduino from the HV by putting the arduino in a grounded enclosed metal box with optoisolated I/O?)
I am also thinking about implementing a fiber optic link for sketch upload also so my laptop wont be attached and damaged(practical/impractical?)


regards
gwen
ps I am NOT concerned about either US patent legalities or actual deployment(except for perhaps as a custom built bear repellant for remote cabins)

[gwenhastings]

Cool!, I just learned from the patent papers that the taser battery is not only overpriced for what it contains.. I found the part number of the memory chip used to distribute the taser firmware updates via the battery sales its a microchip 24AA128 I2c Serially accessible memory.. so I guess the first step is to hook up the bus pirate and try to see if it(the 24AA128) responds to commands next a small routine to dump it(the firmware) into a file for feeding to IDA 6.1(or a preprocessor to same)


gwen

ps confined to bed today by old age and illness ,so I am bored out my skull...(time to catch up on research).

[lyndon]

What do you want to protect the Arduino from? A grounded box won't help if you are trying to protect it from the HV. Not sure why you want to use a microprocessor? A CMOS oscillator is a lot more reliable, and the animals don't really care about the waveform. 5kV hurts anyway you look at it...

Here's the site of a friend who built something similar, but he had a good reason for making it microprocessor controlled: www.rabbitzapper.com

[gwenhastings]

why the grounded metal case(and should read with optoisolated I/O)? Induced HV transients across the input gates of the avr chip.. takes about 100v/cm2 to damage igfets

and the initial circuit will probably switch a 2n2222A/2n3055 pair to the primary of a GM spark coil(which means at least 25kv..)

And to be more precise I am looking at voltages as high as 50kv ,the X26c first stage voltage for creating ionization paths through clothing and also needed to fire the cartridges


if I dupe for research purposes the multiple flyback HV section from the taser patent papers then I am looking at 50kv in the HV section.. with at least 2 transient inducing spark gaps
although both fortunately are not operating at once.

right now I am looking for a 20ohm 5 watt resistor for the HV section using the GM coil:)(the time machine based design)

and again this is to determine methods and means of handling HV alongside of microprocessors..ie a research project..

fence chargers are a dime a dozen and are not really the point of the exercise.

A fence charger that can sense load and back off to safe levels automatically thats a different matter(and still clip weeds or not depending on humidity levels and load and settable options)

A fence charger that could sense heartrate similar to current taser designs and make its shock nonlethal automatically or no shock at all to humans sensed?? very interesting...and useful

special rules DO apply for handling HV such as the induced transient problem mentioned above.
some of the design principles come from a project found in circuit cellar for an ECM(spark and injectors) for a custom engine design a decade back or so.

cheers
gwen
ps this is NOT about the best oscillator circuit for the job, this is about again controlling HV with microprocessors.. fence chargers are interesting because of the many HV design issues but are not really the point of the design exercise..and the arduino or mps430(proto board at $4.30? I will be ordering a couple of those for testing to destruction) are simple and easy development environment(s) for the project..

[gwenhastings]

cool..

looking at your earlier discussion threads lyndon I came across this gem http://reibot.org/easy-high-voltage-supply/ someone had mentioned..

and they also mention the EMP effect(induced voltages)...

gwen

[westfw]

taser.com's x26 taser ... shows considerably more sophistication in the HV section..

Yeah, "taser" tends to be misused in the hobbyist community for any HV shock device, but a "real" Taser (tm) has a lot more sophistication (and "more effect with less danger" than many of hobbyist devices.)

[lyndon]

A fence charger that can sense load and back off to safe levels automatically thats a different matter(and still clip weeds or not depending on humidity levels and load and settable options)

That's similar to what the product I linked to was doing: it sleeps until it detects that something is in contact with the fence then it turns on the HV. I will suggest to him that being able to tell humans from other animals would be a good feature. Actually I'm surprised that it never occurred to me before: being shocked by electric fences is so annoying (and sometimes painful!) that I'm sure that people would pay a premium for one that could tell human from horse/cattle/pig, etc. and adjust accordingly.

It may not be the intent of your project, but you just gave me a great idea

[gwenhastings]

Hi Lyndon,
deciding when it should pulse and how much was always one of the goals of the project and I had planned on somehow picking up heartbeat to make sure the pulse trains were NOT driving whatever hapless animal into heart failure of what ever form. The latest taser patents hint at this..

BTW for the record I am a X26c taser cam owner, which means I have a spare non chargeable Taser(tm) battery with the aforementioned firmware containing i2c accessible memory(not used as the taser cam is chargeable and powers the entire taser). The programming loaded via the battery is the only thing different on the x26 series between the law enforcement and the civilian model(the civilian model shocks longer and harder automatically allowing one to escape,leaving the taser on the ground attached to and shocking the assailant immobile(TASER.com replaces the device if a police report is filed and handles any lawsuit should their device kill someone)). I also own many stun devices(alive,mostly dead, and scavenged)from the original NOVA XR-5000 up to and including the amazing concepts Phasor-1 a lab built capacitive discharge based stunner(very dangerous massive dc pulse at 3-5kv with about 8 joules of energy.. almost killed me...by accident) .
btw the original safety eval on the nova xr5000 is here and an interesting read.

http://www.securityprousa.com/nostgutein.html
has a lot of technical safety criteria of how to avoid ventricular fibrillation with the generated waveform.

In the early days of Taser(tm) I also used to own 2xm18 stick taser(s) the ones with the lousy safety slide switch and managed to shoot myself in the groin in front of a carpet cleaning guy,never ever stick a taser in your pants pocket, same goes for stun guns and in the chest.. in my bathroom taking a pee, never stick a taser in a coat pocket etc ..
Both times I experienced some discomfort but NOT the life threatening blast of the phasor one
ie the X26c is reputed to be a lot stronger and thats fine I DONT need to test that one personally

Deciding the final pulse shape and train is why I am interested in have the microprocessor control same so that the shock is more effective at disablement while NOT presenting a life endangering threat .

Door or window taser anyone? how about a taser wall? they already tried taser landmines.


gwen