Christopher Ooi

I am doing a project which is an Anti Car Theft System. If the thief touches my steering lock, the steering lock will provide high voltage to shock the thief. Please help.

Phasor

A project like this has a major failing, and that is, that there needs to be a return path for the current, regardless of what voltage you use. How can you be sure that the prospective thief is effectively grounded to your car?

Unless you embed a metal mesh mat into your seat, or provide other means of grounding the thief, this idea MAY not be successful.

kinjalgp

Yes you are right Phasor! To get a shock you need to be grounded.
But if the potential is very high (few thousands of volts) you definitely need not be grounded to get a shock of your life. The same principle is used in newly developed electric guns which is used by police to temperorily disable naughty guys

Kinjal

mechie

Sorry, you DO need a circuit - this has to include a return path of some sort !
Even Mother Nature has to have a return path for lightning strikes :!:.
The little 'tazer' type devices have two terminals for this reason.

In the UK I have watched the 'transmission' guys working on LIVE overhead 400kV power lines between pylons by being lowered from a helicopter onto the line. To them the line is earth and the planet is 400kV :shock:

Christopher Ooi

I am sorry that i never tell you all that i am using three 9 volts dc battery and provide more than 200 volts. What i want to do is actually the same idea as kinjalgp idea where the police uses the electric guns to temporary disabled the naughty guys. I get this idea from a company called Air Taser. What should i do to step up high voltage like this?? Should i used any ICs or any special dc to dc converter circuit?? Please help. Thanks for all urs opinion.

kinjalgp

Hi,
The simplest method to generate peak high voltages is to use UJT relaxation oscillator, output of which is connected to a step-up transformer. The output voltage will depend on the Turns-ratio of the transformer (i.e Output/Input) . Higher the ratio, more will be your output voltage. One special thing about UJT relaxation oscillator is that it produces sharp pulses at its output which are perfect for our purpose. These pulses are of amplitude nearly about your Vcc so you need to amplify them whihc is done by the step up transformer.
Instead of UJT you can also use IC555 in monostable mode (single shot) to generate only one pulse or in astable mode (free running) to generate train of pulses. Now apply these pulses to a transistor and drive your step-up transformer.

Kinjal

mechie

Have you looked at the Projects forum here on ETO ?
Specifically ...
. Stun Gun (uses 555 timer)
. Strobe light (uses two transistors)

Both will generate a high voltage from battery power.

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Christopher Ooi

Thanks a lot for all the information...It help me a lot...Thanks kinjalgp, mechie...

vfgilber

Hi,
I was looking at the proposed stun gun plan using the 555 timer, however, the description says that voltage steps up to about 1800v. This is pretty weak compared to most stun guns that run 50,000 to 100,000v. Can anyone comment on this?

Phasor

1800V is certainly not "weak"! It depends, though, on the physiological effect you are trying to achieve. 1800V (at low current) may not "stun" a person, but it definitely hurts ALOT :twisted: (I have had it done to me, several times, when I least expect it!).

If you go to a source which is NOT current limited (such as your local substation), this is a different kettle of fish - 1800V = deep fried internal organs

lavenatti

A high voltage wire from the ignition coil would make life easier. Just use a HV relay to switch between the distributor and the wire to the steering wheel (or seat). It'll be shocking and the car won't start.