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

Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
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Hotwired
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Fri Mar 09, 2012 4:49 am

Okeydoke.

If that resistor is the only one at that end of the circuit board then it's a bleed resistor between the two terminals of the capacitor and is likely to be arcing from feedback from the coil.

You don't need it, it is there to discharge the capacitor when you turn off the bug zapper so there's no charge left on the grid you could zap yourself with.

For a faster spark rate you mainly need to think about changing the capacitor.

I believe the one on the circuit is larger than needed. The one I'm using is a .22uf one. Because it holds less charge it reaches the voltage needed to jump the spark gap faster.

Don't know how you're finding an air gap but I had a heck of a time having a reliable one and over time and with a fast spark rate the points tended to corrode after a bit. If you can get hold of a 200-300v sidac or gdt it will be much easier. Or lower rated ones chained together for the desired voltage.
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Fri Mar 09, 2012 9:36 am

oh okay thanks for the help ill see how the new circuit works out cause its a little different then the old one. if the resisters starts sparking like the old one I'll try cutting it off.

i cant really find a .22uf capacitor with a voltage as high as 400. not with out going online and I'd rather not buy anything online cause it turns a 1 dollar item into an 11 dollar one with shipping. I'll see what the rate is once i ad in a proper spark gap.

and yeah the air spark gap was just for testing it. just to make sure everything worked you know. i will add in a gdt or a sidac. its just I'm having a devil of a time finding them. radio shack has sidac's but not at that voltage. but if i can chain them together then i guess it works out. do i put them in parallel or series?
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Fri Mar 09, 2012 7:00 pm

Anywhere from 0.1 to 0.47 will be suitable, it isn't a precise circuit. 0.1 microfarad caps are usually in the power supply filter in most switchmode power supplies.
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Fri Mar 09, 2012 9:24 pm

you know radio shack does have 400 volt 0.47s i can run over tomorrow and pick one up. thanks
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Sun Mar 11, 2012 10:55 am

okay so i found these sidac's http://www.radioshack.com/product/index ... ndSrc=cart do you think they will work if i chain 4 of them together?
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Technician1002
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Sun Mar 11, 2012 11:37 am

Most of those type diacs are used to trigger triacs in a light dimmer. As such they have a typical breakover voltage of somewhere between 6 and 20 volts. They are a trigger device, not a power switching device. Use with an SCR or TRIAC to get the higher voltage desired.

Edit. I looked up the data sheet on that one. It is 90 volts, not for a light dimmer.
Google NTE6418
Applications:
D High Voltage Lamp Ignitors
D Natural Gas Ignitors
D Gas Oil Ignitors
D High Voltage Power Supplies
Xenon Ignitors
Overvoltage Protection
Pulse generators
Fluorescent Lighting Ignitors

Their typical use is as shown below. When the cap is charged to about 10V the DIAC breaks over triggering the TRIAC This could be used with a voltage divider to use a lower voltage trigger diode with a higher voltage SCR or TRIAC instead of cascading the diodes. A triggered triac or SCR can handle much higher current. I have a 300 Amp 600 volt SCR in my shop.
Image
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Sun Mar 11, 2012 1:06 pm

Technician1002 wrote:Most of those type diacs are used to trigger triacs in a light dimmer. As such they have a typical breakover voltage of somewhere between 6 and 20 volts. They are a trigger device, not a power switching device. Use with an SCR or TRIAC to get the higher voltage desired.

Edit. I looked up the data sheet on that one. It is 90 volts, not for a light dimmer.
Google NTE6418
Applications:
D High Voltage Lamp Ignitors
D Natural Gas Ignitors
D Gas Oil Ignitors
D High Voltage Power Supplies
Xenon Ignitors
Overvoltage Protection
Pulse generators
Fluorescent Lighting Ignitors

Their typical use is as shown below. When the cap is charged to about 10V the DIAC breaks over triggering the TRIAC This could be used with a voltage divider to use a lower voltage trigger diode with a higher voltage SCR or TRIAC instead of cascading the diodes. A triggered triac or SCR can handle much higher current. I have a 300 Amp 600 volt SCR in my shop.
Image
so that means what i cant use them. you'll have to forgive me its been a long time since my electronics school days. and i never was very good with the engineering.
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Sun Mar 11, 2012 1:27 pm

well either way i might as well go with this since i gotta buy online anyway.
http://il.farnell.com/jsp/search/produc ... ku=1827763 what do you think will it get the job done, the data sheet for its in a link on the page right next to the pic. thanks for all the help on this everyone. also any one ever use this site before? i want to make sure its legit.
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Sun Mar 11, 2012 4:07 pm

that sites no good charge a minimum order of 20 bucks. how about this one http://www.ebay.com/itm/MKP3V240-SIDAC- ... 563dca7728 think that will work? voltage is a little low but i do get 5 so i can chain 2 together and just use a bigger cap.
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Mon Mar 12, 2012 4:28 pm

saint .357 wrote:that sites no good charge a minimum order of 20 bucks. how about this one http://www.ebay.com/itm/MKP3V240-SIDAC- ... 563dca7728 think that will work? voltage is a little low but i do get 5 so i can chain 2 together and just use a bigger cap.
so is that a yes on these cause i kinda gotta move fast before the sale ends.
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Hotwired
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Tue Mar 13, 2012 4:45 am

One of those should work.

For reference, the GDT I use are 330V and the SIDACs were 330V, 240V is fine.
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Tue Mar 13, 2012 6:40 am

i know but the only sidac i could find on eBay was that 240 one. umm where did you get yours if you don't mind me asking?
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Hotwired
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Tue Mar 13, 2012 7:07 am

Online electronics suppliers but ebay can be helpful sometimes.

Yes they tend to have minimum orders which are fairly high for hobby buyers after a couple of components.

240V will work.
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Tue Mar 13, 2012 10:53 am

thanks for all the help hotwired I'm ordering them now.
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Tue Mar 13, 2012 4:15 pm

i also hit up radio shack and got some 500v 0.0047uf capacitors to replace the ones in the circuit. but there really small. did i fuck up and get ones that wont work. i know Zeus said 0.1 to 0.47 but i didn't notice the extra zeros in mine till i got home. are they too small or will they give me a faster cyclical rate?
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