How to: Make a stun gun with a disposable flash camera

[Hotwired]

I did have those type of sparkers. Had about 10 of them.

But the point was to make a circuit which could pulse a high voltage coil by starting with a flash camera.

How much value it is to you depends on what resources you can get for free and how small you want to make it and how much being different is worth.

At a minimum you could have the charging circuit for free, a replacement capacitor scavenged from electronics, a spark gap can be an open air manually adjusted one and an ignition coil from scrap.

Or you could start with the free camera circuit, buy a capacitor, spark gap and HV coil and pimp it exactly as you want.

Either way you end up with an automatic high voltage spark generator which operates in the same way as a stun gun and is quite effective at ignition.


Financially it makes no sense to obtain anything better than a piezo for ignition, if a piezo won't light it, it wasn't going to.

But if you don't want a piezo, can't get a stun gun and can't get a battery powered gas ignition box then this guide can help you make something up.

[Zeus]

I concur with Hotwired, it isn't because you need one, but making something more effective than a commercial device is immensely satisfying.

I frankly never want to see a piezo again in my life (I don't mind piezo tweeters though).

Well my attempt at a circuit based minimisation failed, and my spark gap wasn't working, so I'll do a dead bug minimisation and add a Cockcroft-Walton multiplier so an open air spark gap will be practical.

[Crna Legija]

I have a transformer from the inside of a phone charger can i use it to bump up a 9v battery? if so ill get pics up for help on wiring it.

also if i run 9v though a car ignition coil how much roughly will come out other end? it can ark about 2-3mm in open air

[Zeus]

Well with a phone charger you "might" be able to get a few hundread volts out of it. Remember that 1000 volts will jump 1.1mm.

And a 9 volt won't do anything for a car ignition coil, unless you use a capacitor charging/discharging circuit like this one.

[Crna Legija]

Well with a phone charger you "might" be able to get a few hundread volts out of it. Remember that 1000 volts will jump 1.1mm.

ahh dam i think i de-soldered a transformer from a old Casio camera it was working for while then stopped so i de-soldered it and the cap for parts

And a 9 volt won't do anything for a car ignition coil, unless you use a capacitor charging/discharging circuit like this one.

yeah i know i was using it to see if i could get it to work, should have asked how much of a boost does a car ignition coil make?

[Zeus]

Ignition coils aren't like standard transformers, most transformers work like gears, 10:1 ratio, 12 volts in 120 volts out, etc.

An ignition coil needs the condenser from a car to work well, and a lot of current. Ignition coils will work well with Hotwireds' design, you'd be looking at arc length around 30-40mm minimum.

[Hotwired]

yeah i know i was using it to see if i could get it to work, should have asked how much of a boost does a car ignition coil make?

The turns ratio in your standard ignition coil is about 100:1 so the voltage in is multiplied by about 100.



Box making is tricky. Hack plastic to approximate shape then grind to fit seems to be the way to do it:



It's coming in exactly on size, 6x4x3cm. Only tacked the panels so far with dabs of hot glue, still not 100% on where to put the switches and how to secure the lid while still being able to extract the battery.

[wyz2285]

I found a coil in a BBQ ignitor, but I only found 3 wires one it
there should be 4 I thought 2 for input 2 for output, right?

[saefroch]

Two are probably input, the third is probably output. There is probably a metal surface that is the other electrode. That or it just arcs to ground.

[wyz2285]

correction: there are 4 wires, but one of the output is connected to a input what shuol i do?

[Hotwired]

So one of the inputs is ALSO where the HV output returns to.

Not a problem at all, you arrange a wire coming off the correct input for the HV to spark to.

It's how an ignition coil works: http://www.sentex.net/~mwandel/cannon/sparky.html

The black coil I've used in one picture is a 3 wire type.

[Technician1002]

Ignition coils aren't like standard transformers, most transformers work like gears, 10:1 ratio, 12 volts in 120 volts out, etc.

Actually they are a normal transformer. How it is used is the difference. Ignition coils have about 1:150 turns ratio. If you feed high frequency AC in the primary ar 300 volts you get 45,000 volts out. CDI and flash circuits dump in the ~200-300 volts to generate a spark.

In the old style ignition with a condensor, simply breaking the circuit with the points creates this voltage spike on the primary of about 150-250 volts. If you touch the leads on a running ignition coil, this will get your attention. This is due to Inductance.

A reference I found mentions only a 100:1 turns ratio.

Typical points ignition systems produce a 250-volt spike in the primary side of the ignition system when the points open. This 250-volt spike feeds the primary coil that then induces a corresponding voltage in the secondary coil. By winding more turns of wire on the secondary coil than on the primary coil, a voltage step-up can be produced. The degree of voltage step-up that can be induced in the ignition coil is generally proportional to the turns ratio. For example, if there are 100 secondary turns for every one primary turn, there will be a 100:1 turns ratio, causing a 100:1 voltage step-up ratio.

Reference source.
http://www.hotrod.com/techarticles/ignition_coil_tech/

The quoted text does contain an error. The truth is the voltage generated in the primary by the changing magnetic field induces a high voltage in both coils at the same time because the lines of flux cross both coils at the same time. The voltage on the output is in direct proportion to the voltage on the input based on turns ratio.

[Hotwired]

Goddammit.

I don't know if it's the massive quantity of ozone it produces or just the loud and harsh crackling of the arcs.

Either way I have a headache like a throbbing bruise in my brain :sad1:

The stungun is totally completed now but media will have to wait on sleep.

[Hotwired]

I did have ideas to add a few status LEDs, maybe a battery switch and some kind of safety switch.

Maybe next time.

Instead there is no power switch to disconnect the battery and one push button starts up the circuit.

But since safety is something I never overlook, the one button is a 1.5mm high 6mm diameter rubber dome which depresses about 1mm to trigger the circuit. Not a lot short of a finger pressing directly on it will cause the circuit to start up.









Minimalistic eh?

I think it looks like some kind of small cupboard.

The shell is 2.5mm PVC, essentially I turned the circuit into a brick of hot melt glue and pasted five sides of the box on. The sixth side is the top which is held on by friction and double sided tape (there is a fair bit of flat surface area for this to be viable). The switch is fixed within the box and the orange actuator in the lid presses on it.

Effectively the circuit is sealed in for life, if I make a second version then it would be from scratch.


Talking of a second version...

With the same components I'd say I could make it about 25% smaller a second time round. Each section in there is wasting space because it was arranged in a simple "box" allocation of space for each part, coil, circuit and battery. I could change that so each section overlaps somewhat like triangular prisms.


One last thing....

My skills of one handed assembly and operation while filming badly:

[youtube][/youtube]


Your turn now, you have all the knowledge you need

[jackssmirkingrevenge]

Very nice! Looks like it would fit in a largish pistol grip...