A stun gun is a weapon that uses electricity to temporarily paralyze a person. The short pulses of high energy cause the muscles to expand and contract very quickly, using up energy and causing them to temporarily lock up. They are sold as self-defence weapons in most european countries and the US. The British police will probably be using them soon. Typically, the voltage range of a commercial stun gun is between 50kv and 300kv.
Background to the project
For the past three years or so, I have been trying to construct an improvised stun gun in my spare time. It started out when I was searching for stun guns on the 'net, and then started searching for stun gun circuits. I couldn't find any, apart from a few rather sketchy patents. The circuits I found that claimed to be stun-guns were simply high voltage generators that could put out a couple of thousand volts or so. While unpleasant, this type of device would not have the effect of paralyzing the muscles.
I designed a couple of circuits of my own, and built one. Those of you who have been following this project since it began will remember them. The first design was similar to my current design. It used two transformers, one that would charge a capacitor up to a thousand volts or so, and then discharge this into a transformer. I never built it, although it is very similar to the current design. The second design (which is still on the site, the HV generator) used a multivibrator to step battery voltages up to between 1000v and 1500v, and then use a Cockroft-Walton voltage multiplier to step it up to about 8000v. The maximum output voltage using this setup is only limited by the number of stages in the multiplier and the ratings of the components. Unfortunately, the output is still not the high voltage generated by commercial stun guns, although it would be painful, and with a big enough capacitor in the final stage could be fairly effective. The spark would be an effective deterant, since a capacitor discharge is very bright and loud.
Self defence in the UK
One of the reasons I'm putting up this information is as a protest against British laws covering self defense and weapons. In the UK, if you shoot a burglar, you'll get a far longer sentence than the burglar (or rapist, you don't know their intentions when they break in) would get if you'd left him to it; look at the Tony Martin case. I suspect this would be the same if you stabbed or clubbed a mugger in the street. The attitude of the police is 'don't fight back', or 'use reasonable force'. It's not going to be easy for someone who doesn't deal with violence in everyday life to judge what is reasonable force to use on a career criminal, who's intentions are not known. The police themselves seem to have trouble judging what is reasonable force to use, given the number of fatal shootings of unarmed people recently.
It is illegal to carry anything that could be used as a weapon, unless you have a good non-self defense reason, such as a builder carrying a Stanley knife in his toolbox. The burden of proof is on YOU, not the policeman.
Having said this, what are the chances of getting caught carrying a weapon? I rarely see police patroling the streets, let alone the dark alleyways and paths that must be passed through to get home for many people. They seem to be more interested in catching speeding motorists, and raking in the cash from fines. CCTV is also a favourite. The more cameras, the less police they need on the beat. When someone gets mugged or raped, who cares if they couldn't defend themselves or that there were no police around? The fact that the crime could have been prevented in the first place doesn't seem to matter.
People who are against the use of stun guns and pepper spray (also illegal) would argue that these weapons would be used by criminals. Personally, I'd rather be attacked by a mugger wielding a stun gun than a mugger wielding a knife or gun. I'd also rather use a stun gun to defend myself, rather than risk killing someone and getting a jail sentence.
This brings me to the handgun ban in 1997. There was no point at all, gun crime and other violent crime has continued to rise regardless. It just shows how low politicians will stoop to get cheap votes and momentary popularity, and how the public are manipulated by the media for their financial profit. We are being disarmed and forced to depend on the state for protection. Personally, I'd rather have the means to defend myself than rely on someone else.
Just to clarify, I'm not anti the police at all. I just think everyone should have the capability to defend themselves.
Anyway, rant over!
100% Improvised
The whole point of this project is that the device can be constructed easily, with readily available components. There is no need to buy miniture high voltage transformers, that are difficult (or impossible) to get hold of. All the components can be sourced from junked consumer goods (although the UJT, SCR and enamelled copper wire would be easier to buy than find). Unlike the previous design, the high voltage capacitor used can be easily sourced from an old TV if a few modifications are made.
Intended audience
You don't have to be an electronic hobbyist to build this circuit if you're patient and willing to learn. It could be a fun way to get into electronics! But it will be difficult, and require a lot of effort. If you get disheartenned or frustrated, leave it for a couple of days and then start work again. Unless you have a well stocked lab/unlimitted cash, there will be a lot of waiting around for parts to arrive/be bought/found anyway.
I have tried to provide as much advice as possible, but it isn't intended to be a beginners project.
Parts sourcing
| Part | Description | Rough Price | Equivalents | Comments |
| C1 | 10uF 25v Electrolytic | £0.10 | Any cap of roughly 10uF that will handle the circuit voltage. | Readily available |
| C2 | 1uF 25v Electrolytic | £0.10 | As above but around 1uF. | Readily available |
| C3 | 1uF 850v | £4 | Cap between 1 and 2uF that can handle peak voltage from rectifier. | HV caps can be found in TVs and photoflash units. Check the voltage rating! |
| R1 | 220 ohm 1W | £0.03 | Roughly that value, at least 1W | Readily available |
| R2 | 1K ohm .25W | £0.03 | Roughly that value, at least 0.25W | Readily available |
| R3 | 500K ohm preset (trimmer) | £0.50 | Any preset of 100k or more. | Readily available |
| R4 | 27K ohm 0.25W | £0.03 | Roughly that value, at least 0.25W | Readily available |
| R5 | 100 ohm 0.25W | £0.03 | As above | Readily available |
| R6 | 10K ohm 0.25W | £0.03 | As above | Readily available |
| R7 | 220 ohm 0.25W | £0.03 | As above | Readily available |
| D1-D8 | 1N4008 | £0.10 | Anything of circuit voltage spec for D1-D7, D8 should be 1N4007 or better. | Readily available |
| Q1-Q2 | 2N3055 | £2.50 | NTE210, or any NPN transitor of about the same power rating. | Readily available |
| SCR1 | TYN810 | £ | 2N4443, or any SCR that will handle this power level. | Many alternatives, check that they can handle the power. |
| UJT1 | 2N2646 | £ | ? | Standard item, should be stocked by any supplier |
| T1 | ~1:75 step up | £- | - | See text |
| T2 | ~1:95 step up | £- | - | See text |
| 0.125mm ECW | £? | Any ECW of about that size | Sold on reels | |
| 0.25mm ECW | £? | Anything up to ~1mm | Sold on reels | |
| Ferrite Rod | 3+ inches long | £? | Any ferrite rod of correct size | Scavenge from broken AM radio. |
| RM10 core kit | Ferrite transformer core kit | £2.50 | Any ferrite core of correct size, including torroidial. | Torroidial cores can often be scavenged from scrap equipment. |
If you can't find an electronics supplier (this won't be a problem in the UK), it will be difficult as you'll have to find equivalent parts from junked items. If you can't find a particular part, there will be many equivelants. I have listed some on this page, along with things to bear in mind when finding others. By far the best thing to do is to buy everything as specified, then you'll know it's all working fine and any errors are your own fault ;-) There are many electronic suppliers (some mentioned in the links section) in the UK that stock nearly all the parts needed.
The Circuit
The
circuit was designed by c0deblue. It uses a pulse oscillator to step the battery
voltage up to several hundred volts AC. This is rectified, and used to charge up
a high voltage capacitor. The capacitor is forced to dump it's charge into the
primary of T2 at a rate set by preset R3, normally many times per second. T2 is
a very well insulated open core transformer would on a ferrite rod, that steps
up the several hundred volts to many tens, even hundreds of thousands of volts.
This very high voltage creates a crackling spark between the two secondary
terminals of T2.
Construction
The following is a rough guide for people unfamiliar with building circuits. I've tried to present it in a clear way, but you'll still need to think carefully. It's not a '1, 2, 3' list of steps, you can do things in the order that you want. I hope that it will answer any questions that come up when you build it, rather than provide a strict construction guide.
If you're used to building circuits, all you'll need is the schematic and stripboard layout, as well as the information on how to wind T2. You might want to check out the troubleshooting section, in which I've detailed possible solutions to problems that might crop up.
If you use the parts that I have listed, you can construct it on stripboard straight away. If you are using any substitute parts, it might be an idea to construct it on solderless breadboard first (if you have one) to make sure it's all working.
Prepare the stripboard according to the layout shown in the diagram below by cutting it to size and using a drill to break the tracks in the places shown. Note the arrow indicates that the tracks are vertical, and the blue lines indicate jumps (wires connecting tracks).
Solder
the components from the first 'stage' of the circuit onto the board. It's best
to do this in order of size, i.e. links, resistors and diodes first, then the
preset, and finally the caps and UJT. Doing it this way helps to prevent the
parts from falling out when you turn the board upside down to solder them in,
since the components will always be resting on the work surface. It also helps
to bend the wires slightly before turning the board upside down, jamming the
components in place.
The high voltage part of the circuit will not be constructed on the board in
the conventional way, to prevent any arcing between tracks. Arcing shouldn't be
a problem in a working circuit at the voltage specified, but I decided to take
the precaution anyway. The current will take the path of least resistance, and
this will be through the wiring rather than the air if the circuit is working
properly! To give an idea of the breakdown voltage of air, a rough rule is 1000v
DC per mm (depending on electrode shape). Solder the diodes together to make the
rectifier as shown in the next photo. Try to make the unit as compact as
possible.
Solder the SCR onto the underside of the board. Solder R7 and D8 directly
onto the pins of the SCR according to the schematic.
Winding T1
T1 is wound on a small closed core ferrite transformer. The turns ratio of
the primary and secondary will depend on the voltage you wish to get out. To get
out 675v from 9v, I used a transformer with 1500 turns on the secondary and 20
on each of the three primaries (1:75). The only reason I used so many turns on
the secondary was because I already had one lying about ready wound. It was a
very tight fit, so I recommend using around 1125 turns on the secondary and 15
on each primary. This will give the same step up ratio, without much (if any)
loss in efficiency.
The secondary is wound onto the coil former (bobbin) first. I used 0.125mm
diameter Enamelled Copper Wire, but this isn't critical. So long as all the
winding will fit, any guage wire can be used. Solder the end of the enameled
copper wire onto one of the pins, and wind 1125 turns onto the bobbin. Try and
keep it fairly neat to give even turns distribution and allow plenty of space
for the primaries to be wound on afterwards. When done, solder the other end
onto another pin. Check for continuity with a multimeter. If there is no current
flow, re-solder the wire for slightly longer than before (to melt the enamel).
Wind a few layers of mylar tape onto the secondary to provide insulation.
Wind the primaries on in the same direction as the secondary. I used 0.25mm
wire, anything up to 1mm can be used without taking up too much space. Solder
the ends of each primary onto pins on the bobbin. You'll need to remove the
enamel using some sandpaper from the ends of the primary wire to ensure a good
connection, as it's thicker.
Final Circuit Construction
Solder some wires onto the base and emitters of Q1 and Q2, and solder these
onto the board. Solder wires onto the cases (collector) of the two transistors,
and solder these to the appropriate transformer terminals. Solder the other
primary connections onto the board. Solder the secondary terminals onto the
inputs of the rectifier.
Attach the capacitor to pin 2 of the SCR. The circuit is now complete, apart
from T2 and the power connections/switch.
Constructing T2
T2 is an open cored ferrite transformer. This means that the ends of the core
are not connected, as they are in T1. You will need a ferrite rod, which can be
found in an AM radio receiver (includes LW, MW etc). T2 will take several days
to construct, so be patient!
Insulate the rod with around 8 to 10 layers of mylar tape. Spray the tape
with a layer of acrylic spray. Wind 200 turns of thin (I used 0.125mm) ECW onto
the rod, securing each end with some tape. You must leave at least 1/2 an inch
space from the end of each winding to the end of the core, to avoid arcing.
When constructing my transformer, I sprayed one coat of acrylic spray onto
each winding, and insulated it further with 5 layers of mylar tape when the
acrylic spray was dry (usually one hour).
Leave 1/2 an inch of wire trailing from the end of the winding. This is not
easy to explain; think of the wire running out of the end of the layer of turns,
the layer of turns being covered in tape, and then running back to start the
next layer of turns on top of the insulation. I have drawn a diagram to try and
explain it:
When you have wound the final winding, spray around 4 coats of acrylic spray
onto it, and further insulate it with 14 or so layers of tape. This is a rough
guide; I don't know exactly how much to use.
Attach some wires to the ends of the secondary winding. You might want to do
this at the stage (below) when you apply the Silicone sealant, since it can be
used to secure the wires.
I then took a piece of paper and wound it around the transformer so that it
extended about 1/2 an inch beyond the end of the windings (including the
trailing wires). I soaked this in acrylic spray, and left it to dry. This was
wound back onto the transformer, and secured with another 5 layers of mylar
tape.
The primary is then wound onto the transformer, above the secondary winding.
It is secured with mylar tape. I used 0.25mm wire, as with the secondary
anything up to about 1mm is practical.
The primary of T2 is now connected to the circuit as shown in the schematic.
Place the two terminals of the secondary winding fairly close together (maybe 5
to 10mm). Power up the circuit, and adjust R3 until you get some sparks! Power
down the circuit, and move the electrodes to around 3/4 inches apart. You should
get a nice loud arc, firing at between 3 and 10 times per second. I wouldn't
advise moving the electrodes more than an inch apart, as this could cause
internal insulation breakdown.
Video's
I've made a couple of video's using a webcam. These show the final
constructed device, and give an indication of the spark length. They are in exe
format, due to the software that came with the webcam.
Housing
I'm not going to provide much information on putting this into a case. I
haven't put mine into a case yet, because I haven't had time. I have 'shaped'
the completed device to allow it to fit into a 12 inch length of 40mm (outside
dia) PVC waste pipe. I will mention some things to bear in mind:
Make sure none of the components metal parts are touching, particularly pay
attention to T1 and Q1/Q2. You may need to apply mylar tape to the cases and
insulate the terminals with Silicone sealant.
Keep all wires to the minimum length required. This makes a neat circuit, and
will help the device fit into the case with ease.
T2 will require some additional insulation of the wires, since they will
probably be held flat alongside the transformer (depending on your intended
case). I used standard insulated wire for primary and secondary leads. In
addition, I added several layers of mylar tape to the primary wires, and I used
some heavy dute mains earth cable insulation for the secondary wire that I had
to have flat against the transformer (the second one simply comes out of the
end, so it isn't in contact with the outside of the transformer).
Modifications to Voltage
If you can't find all the parts listed, you'll have to look for equivalents,
sometimes in junked items. If you can only find a capacitor of a lower voltage
than that required, you'll have to slightly modify the circuit to keep the
voltage generated by T1 below that value. This doesn't have any effect on the
final output voltage if you change the ratios of both T1 and T2. Some advice
when changing ratios: keep the number of primary turns above about 20 on T2 and
10 on T1, otherwise the coil will not saturate.
Troubleshooting
There are many things that can go wrong with electronic circuits in the
construction stage. In most cases, they need a little tinkering to get working.
I've provided a short list of likely problems. If you have any problems and are
REALLY stuck, email me and I'll have a think (if I think you've tried hard
enough on your own, I'm not running a technical support service!).
If you've had trouble getting it working but solved the problem, I'd like to
hear from you so that I can include it here.
Q. There's a buzzing noise, but there's no spark! Q. The buzzing noise doesn't increase in frequency over time, and there's no
output. Q. The circuit's dead! Q. Could it be T1? Q. I've tried everything, but it's still dead. Advice on use
As of yet, I haven't tested it on anyone(!). If I have the misfortune to have
to use it, I'll share the results. In theory it should work just as well as a
commercial stun gun. What I'm trying to say, is that I make no guarantees. Even
commercial stun guns aren't always effective according to some people. While it
may work well to immobilise a 9 stone junky, I wouldn't want to use it on an 18
stone bodybuilder. What it will certainly do is be a deterant. The spark is
bright, especially in the dark, and it is very loud! You may avoid a fight,
especially if your attacker isn't a seasoned thug. They might go away and find
an easier target. That's the theory anyway ;-)
Future Modifications/Misc thoughts
This circuit is similar to my first ever design, which I abandoned long ago
because I didn't think it would work. The differences being that it used a less
efficient oscillator to step up the battery voltage, and it used a spark gap
instead of an SCR. At the time, I had no idea how to construct/obtain a high
voltage transformer (T2).
Anyway, for better improvisation, a spark gap could be used instead of the
SCR/UJT combination. The disadvantage of a spark gap would be that the
electrodes would soon oxidise, requiring that the gap be replaced eventualy. If
you are familiar with electronics, you may want to try this.
At present, the device is putting out between 2 and 3 joules of energy per
second. This assumes that the capacitor is charging up to around 750 volts on
each cycle, something I can't measure because I don't have a CRO. It also
assumes around 8 or 9 pulses per second, and good transformer efficiency. A
commercial Taser puts out around 6J per second. I would like to construct a
higher powered version in the future, that puts out between 6 and 10J per
second, at a slightly lower voltage (no more than about 50Kv). I would
accomplish this by using a higher voltage cap.
Feedback
Spotted any errors? Any constructive criticism? Have you had to use this (or
any other stun gun) in self defence? I'd like to hear from you! Email me at thejuice2000@hotmail.com
Thanks
I would like to thank c0deblue for his help with this project. He gave me the
circuit, and some very helpful advice throughout.
Copyright etc
I don't mind if this information is re-distributed, provided:
1. ALL information is present, and there are no modifications made. Created by J (The Juice), published 28th September 2001
Note that the board in the photo is too small by one track (far
right). This was a design error!
These are the pin outs of the Semiconductors used.
Now
solder the rectifier onto the underside of the board, leaving a few mm space
between the pins (except the earth) and the board tracks. The complete underside
is shown here (with wires; the photo's weren't taken in sequence):
At
this stage, you might want to test it to make sure it's working. A car ignition
coil works well as a substitute for T2, although it won't give such a powerful
output. Attach a wire to the middle terminal, and attach an earth to one of the
others. Connect the capacitor to the remaining terminal, and adjust the center
terminal wire so that it is about 15mm from the earth terminal. Connect up a
power source (a 9V battery will do), and you should get a spark arcing from the
center terminal to earth. If you don't, adjust preset R3 until you do. If you
still get nothing, go to the troubleshooting section below.
The
number of windings you have will depend on the voltage you wish to get out for
the voltage you put in. I have a total of 3800 turns on my transformer, with 40
turns on the primary. If I were to make another one, assuming the 750v input, I
would use around 2000 turns on the secondary and 20 on the primary. I initially
operated my transformer with 250v pulses, but I then increased the input to
750v. At 20 turns on the primary, the insulation broke down straight away.
Fortunately I was able to repair it without re-winding the secondary.
The
secondary requires additional insulation at the ends of the windings. Due to the
spray saturated paper, there will now be a cavity at each end of the
transformer. This must be filled with Silicone sealant as thoroughly as
possible, no air bubbles must exist. This is left for 24 hours to cure fully.
The next photo shows the sealant at the end of T2:
Testing
This photo shows the circuit connected to the cap and T2.
A. It's probably
charging up (if the buzzing noise increases in frequency over time) the
capacitor, which is good. Try adjusting R3 from one extreme to another. If
there's still no output, try triggering the UJT manually. This is accomplished
by touching a wire from the positive supply rail to pin E as shown in the pinout
diagram. If there's no spark, check all connections around the UJT. You may need
to replace the UJT. If there's a spark, you'll need to check the wiring of R3,
R4, R5 and C2 (the UJT triggering block), and possibly substituting different
value components (R3 and C2). If there's still no output, check the rest of the
connections in the circuit block around the SCR. If there are no obvious faults,
there might be a dead component (most likely the SCR) in the HV stage which will
need replacing.
A. The capacitor probably isn't charging up. Check that D8 is
connected properly and round the right way. Make sure that the T2 primary is
connected properly.
A. If there is no buzzing noise, it means the pulse
oscillator isn't working. Check all power connections, then check all component
connections. Make sure that the T1 primaries are connected properly to the
correct places! By far the most likely cause of this is a wiring/soldering
error, or a component is round the wrong way etc. Did you connect Q1 and Q2
properly? If the circuit is constructed on stripboard, run a sharp knife along
between neighbouring tracks on the underside. There are often shorts that are
difficult to see due to tiny strands of solder joining tracks, the knife will
remove these.
A. Yes! Use a multimeter to test each winding for
continuity. If there is none, re-solder the connections made at the wire
endings. If there is still no continuity (especially in the secondary coil)
you'll have to re-wind it with new wire :-( Also check to make sure windings
aren't shorting each other out. If you find continuity between any windings,
you'll have to check the connections carefully. If it's a break in the
insulation (unlikely), re-winding is required.
A. If all the
wiring/soldering is fine, then it will be a dead component. The most likely
culprit will be Q1 or Q2. Resistors and capacitors will usually be visibily
damaged if they are dead, but transistors rarely are. If you have a multimeter
you can test them, if not then you'll have to buy a new component(s) and test
replace the suspected damaged one(s).
2.
There must be NO CHARGE AT ALL made, not even a 'copying/distribution' charge!
This information is free, and I want it to stay this way.
3. It is not put up
as another website without my permission. I will almost certainly update this
page from time to time, having different versions scattered around the web would
be very confusing.
4. If you want to include this information in a magazine
(electronic or otherwise) or CD compilation etc, you must ask. Permission will
only be given if all these conditions are satisfied, and the magazine (or
whatever) isn't 'kewl' (don't know what this means? Do some searching).
5.
There must be a reference back to this website included with the information.
