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Old 25th November 2008, 09:58 PM   #1
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Default Firework ignitor

New year is coming up soon and I want to let off a bunch of fireworks. However, every year I'm the one lighting the fireworks and I'm too busy running for cover to get a good view. This year I want to remotely ignite the fireworks!

I'm looking for a re-usable way to ignite them electronically using only standard batteries (9V or 1.5V) that can be triggered from 30ft away at least and won't drain the batteries in one or two launches.

My first idea would be to put a bunch of 9V batteries in series with a small loop of copper wire which I can attach fuses to, housed in a metal box. I could then set up a relay with a long control wire coming out of the box that I can press and hold a button to ignite the firework.

However, it's a bit primitive and I'm not sure it'll get hot enough to light a fuse. Anyone got a more elegant solution that's guaranteed to work?
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Old 25th November 2008, 10:06 PM   #2
drewmc is offline drewmc  United States
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You don't want to use copper wire for the ignitor, the resistance is too low and melting temp is also too low. Use nichrome wire if you can get it, or thin steel wire. A better battery to use would be a lantern battery or the battery pack from a rechargeable drill as these can provide more current than a 9 volt or other small batteries.
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Old 25th November 2008, 10:29 PM   #3
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Drill battery sounds like a good idea. I can pick up a reasonably powerful battery drill for about 25 at a local DIY store. I have some cheese cutting wire that's made from stainless steel in my kitchen cupboard and I never use it. Random gift I got last year. I might butcher it and use that. It's only about .4mm in diameter, so it should have a decent resistance. I'll be using high-gauge wires within the ignition box so it won't fry the wiring inside the box.

I can't find any sources on the contact ignition temperature of visco fuses (the standard ones used in consumer fireworks), so I've had to do a little research. Visco fuses have a black powder core encased with around 1mm of nitrocellulose coated string. Nitrocellulose has an ignition temperature of around 170 C (and m.pt. is around 160 C) so I could do with 200 C on the wire to keep within a good margin of error.

Do you think a drill battery on a 20mm loop of .4mm steel will produce that kind of heat?
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Old 26th November 2008, 12:01 AM   #4
drewmc is offline drewmc  United States
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Most likely this will get too hot and burn up. you need thinner wire or lower voltage. A piece that long it would be best to use only about 1.5 volts, but high current. A piece that long will likely be only a few ohms.
I remember having a 6 volt NICAD battery as a kid that would burn up a section of iron wire about 0.5mm dia, 150 mm long
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Old 26th November 2008, 12:22 AM   #5
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In my younger years, my friends and I used to use model rocket ignitors for such things. They are available in hobby shops. Just use a little tape to attach them to the wick of the desired firework(s) and then hook up your wires. Hit the button back at your ignition mechanism and the current flows. Ignitor lights wick and BOOM!!!

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Dave
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Old 26th November 2008, 12:30 AM   #6
SY is offline SY  United States
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Nichrome igniters are great; I still have fond memories of my Estes rockets blasting skyward...

If you want to do something more elegant, I've used the flash mechanism from a disposable camera to make a spark igniter. Works like a charm.
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Old 26th November 2008, 12:37 AM   #7
drewmc is offline drewmc  United States
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The only problem with this approach is the igniters cost more than the fireworks.

When I was at college, I fused an entire box of bottle rockets, roman candles, and a brick of fire crackers to a cigarette timer and placed it in the middle of an enormous parking lot. It was clearly visible from my my dorm room balcony. What a spectacle! The campus police arrived, but they had no way of knowing who was the perpetrator.
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Old 26th November 2008, 12:38 AM   #8
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Sy, thanks for the reminder, I was trying to remember the trick a friend at work said he used to use. He took a small halogen bulb and broke the glass bulb off, without breaking the filament. Apply power to this and it gets plenty warm enough to ignite a wick.
I do agree that model rockets are fun. They are really just big, legal fireworks. And if you modify them correctly, you get a really big boom up in the sky!

Peace,

Dave
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Old 26th November 2008, 01:28 AM   #9
SY is offline SY  United States
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Dave, I'd comment, but I'm not sure that the statute of limitations is up.
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Old 26th November 2008, 01:40 AM   #10
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SY, No further explanation or elaboration is necessary. Best to keep things vague.
I also thought of a source for nichrome wire for NinjaKitten. Find a discarded toaster, toaster oven, etc. and remove the heating element. Voila, ignition heat source.

Peace,

Dave
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