Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
This post will probably be deleted but I feel I should warn you about the morality, and legality of building/owning such a device. In many countries it is illegal to possess/buy a stungun, let alone build one. Dispite their reputation, they aren't all that 'non-lethal'. The secondary effects have killed many in the past. Falling, weak-hearts etc..
A couple of questions:
1. What do you mean by 'stungun'? There are many types. Some are designed to cause severe pain (cattle prods, for torture), others, a nasty shock thats meant to just 'put someone off' like an electric fence, and 'tasers' (brand name) which were originally designed to shock the nervous system and render somebody immobile for a brief period of time, and shouldn't really cause that much pain. They are similar, but have different design constraints. After all, being a 'non-lethal' weapon, it shouldn't be able to kill someone directly from its effects on them.
2. Just curious, why do you need one? Or is it purely a technical curiousity?
I take no responsibility for this information.
The schematics of 'store-bought' stunguns I've seen are very simple, inefficient, and not very reliable. Don't know how they can sell them. But the 'basic' priciple is this: Step up a battery voltage (9-18v) to something like 350v. Then use this voltage to charge a high-voltage capacitor of relatively low value. This cap is periodically discharged across the primary of a transformer. Creating very breif pulses of approx. 25-100KV. Every 0.1s or so. If you're designing something to 'imobilise' someone, the timing of these pulses is critical. But it seems that nearly all comercial devices just 'hurt' - poor design.
Now, notice that I said 'pulses'. We have 10 pulses a second, but each pulse only lasts about 2us max. Thats only 20us, a second, of current in total. Thats what makes it non-lethal. And because you are disharging a cap, very quickly, you get a massive surge of current (Q=IT=CV) which, even though the voltage is stepped up through a transformer (so the current is stepped down) can reach into the 'amps' range. Apparently, an av. stungun can kickout 25kW per pulse. Sounds like a lot, but for only 20us a second, we can work out the average energy' per second.
E = P*T
Joules = Watt*Seconds
so, 25000*0.00002 = 0.5J - Thats the equivelent of 500mW per second. And obviously, powered by a 9v battery, the output cannot be greater than the input.
Another thing, I would try not to attempt to build some schems on the net. They use an audio transformer to 'step-up' the battery voltage(with some sort of oscillator) and then a voltage multiplier. These generate DC. Although they only produce 3-4000V at a few mA, because they generate a DC output, the risks of electrocution, and severe burns are great.
I'm reluctant to provide a schem mainly because of the reasons above, and also, my own personal opinion. Plus, it would be a challenge to design your own! But be VERY CAREFUL. Learn to appreciate that:
'its the volts that jolt and the amps that kill' - is not always true.
After all, V=IR, and it only takes a few miliamps to stop the heart. At 4kV, the resistance of your body/skin becomes less significant, and allows more current to pass through it. So DO NOT work with anything 'DC'.
Lastly, don't test it on yourself (NOT pleasant).
As I said, this is probably a pointless post, but I did included some generic info on the device. I'm sorry if I've been patronising, and you know all of this, but a few extra warnings don't hurt.
Heh, sorry, didn't realise you were a full member. Obviously not a kid. Sorry.
Sorry about not taking the easy route and posting a nice schem, but you know, someone could become a member, get the schem, build it, and either seriously hurt themselves, or someone else. I don't want to have that responsibility.
I did make a mistake with the maths. Its 25kW per pulse, but there are 10 pulses per second. So the total energy, per second is, 10*25000(W) * 0.00002 (S) = 5W.
And the current draw from a 9v PP3 battery would probably be about 600-800mA.
The 'pulsing' design that I described is the most complicated (still pretty simple) but apparently yeilds the best results. And its output power is easily controlled by changing values, like the main HV cap. As I said, its really split into two sections:
1) High voltage inverter. To get 9V up to 300-400V easily, you could use a mains transformer, in reverse. I've got 500V out of a 240V to 6-0-6V cheap mains transformer. Using a single transistor that switches one side of the primary to ground, with the centre tap of it connected to VCC. The other side of the primary is connected to the input of a simple voltage divider (10:1), with the output of the VD to the base of the transistor. So, one transistor, and two resistors are all you need to get 400-odd volts AC out from the secondary of the transformer. Rectify with a diode bridge, and maybe use a series resistor to reduce the voltage down to decent value. (since the above configuration, albeit simple, can produce spikes of about a thousand volts very efficiently, because its in resonsance).
2) Discharge section. Now you've got 400V DC (or pulsed DC) you charge your cap with the primary of another transformer in series with it. And for simplicity, a spark gap across you HV supply. As the cap charges, the voltage accross it rises, untill it reaches the breakdown voltage of the air gap (0.5mm?). When this fires, it completes the circuit, dumping all the cap energy intot he transformer primary. Producing a rather angry, fat, arc.
I mean by "stungun" a nasty shock thats meant to just 'put someone off'
Ahh, in that case, it *may* be easier to make a small cheap inverter. But the output of this cannot be so easily controlled. I've been zapped by a 3kV supply, at 2mA, and let me tell you that 'put me off' To keep it safe, you could use a small audio transformer (600 ohm primary, the 1-2Kohm secondary) and feed ing with a 555 timer, controlling a MOSFET. Then, maybe a 'cockroft-walton' multiplier. If you don't know about this, google will have many answers.
That could make little 5 mm arcs, but at DC. Loud and quite intimidating. But prolonged use will burn. You could vary its power by changing the frequency of the 555 timer. OR.....if you're really into electronics use a PIC micro to control the PWM going into the transformer. Maybe with feedback from the transformer output going into the PIC (via a divider network) so you can controll the output very accurately, and program in various pulse patterns. (putting digital controll on high voltage really is a wonderful thing)
OK, now I'm just ranting Good luck. And if you get stuck, or have any questions, PM me.
david90, you have a good point. What is the point of owning a stungun?
If an attacker has a knife, you run. If he (or she, I'm not sexist) has no weapons at all, you hit them. It seems the world is paranoid now
Moderator, feel free to delete this. My apologies.
you might want a stun gun so you can walk your dog in a rural neighbourhood and not feel scared about wild animals.
if this is the case, just go buy a cattle prod.
if you want to protect yourself against other humans a stun gun is no good. go buy a gun, it is the only way. if you hit someone with a stun gun the law suit is the same, "assult with a deadly weapon" even if you try to argue it is not deadly.
[disclaimer] my comments are hypethetical only, you shouldn't REALLY try to ever kill anyone for any purpose. in fact, you should do nothing with what i have typed, just reboot your computer.
Hope your intend is of a good defensive one, whether for education sack or for novelty sack.
The easiest and cheapest way with a "stungun" is by getting a mosquito bat( for less than US$5) and modify it's output to a "spark gap" type. You can bend 2 nail heads close to each other, about 2mm wide, and wire the output to it. Oh, remember to take out the battery before you attempt to meddle with the circuit .
You can safely test it out on yourself! It will deliver a nasty bite, but non-lethal, or else you could see "legal warning labels" on mozzy bats everywhere.