Engineering question

I’d like to see if anyone can help me with a technical issue. I’m busy preparing for the 4th of July. I’m having a problem fabricating an ignition system for a large number of fuses at once.

My first idea was to simply run a car battery to a fine peice of copper wire and hold it tight inside a nonconductive surface, with holes cut in the top to lay the firework fuses inside. The wires from the battery got hot but the copper didn’t. I figured I needed a diode to keep the electricity flowing from the positive, but not back to negative. For some reason, no setup I was using would produce current, although I still had a charge on the battery.

Next I tried using the guts to a toaster, but I couldn’t remove the toast ejector without removing whatever kept the filaments from burning out. From my limited knowledge of electronics, I thought the ejector was a heat based cuttof switch. This I wanted to replace with a momentary switch, but after hooking up the elements sans ejection parts POOF! Instant burned filaments. Im figuring that I removed some sort of Ressistor or Potentimeter, but I just don’t see it.

I’m thinking of taking apart a hair dryer, removing the fan unit and using the coils and heat controls from the unit.

Before I get a lecture, yes I know I REALLY shouldn’t mess with AC power. Yes I know if I am careless, AC can be deadly.

I’m being as safe as possible and using grounded plugs when I test things AS WELL as standing the hell away/removing all power and double checking when working on hardware etc etc. I’ve been working with electronics and electric locks for about 15 years now, and I know what NOT to do (yeah… my hair got frazzled and I started listening afterward…)

I just need a heating element for the max of 3 seconds. I do a show with fireworks and this year we need to set off a large number of works at the same time. Quickfuse is not available around here, and my only contact in the industry got REAL weird when I called them. I don’t feel comfortable buying explosives from people who answer the business phone with a scream.

I’ve been doing fireworks for longer than I’ve been doing electronics and I’ve had NO INCIDENTS. Some of the pros I know can’t even say that.

Anyone with any ideas or links that could help me please chime in.

BTW I know about Rocket igniters, they are what we used up until last year. The problem with them is the fragility of the design. They are made to fit inside a premade hole and light a solid rocket fuel. Attaching them to fuses is hit and miss as they either break or don’t light the fuse half the time…

Nichrome wire is what you’re after. Oh, and no diode; it doesn’t do what you think it does.

For some reason you do not want to use the two best methods. Last summer I made a hell of a show for some friends out at a lake they have a cabin on. Why can’t you get extra fuse? It is the easiest way to go and is available all over. Any place that sells fireworks has it as well as many hobby stores. If you need to you can buy it online here.

I find twist ties work best for attaching fuse together.

The problem is, that with the general public version you get a burn rate of about an inch a second. That’s ALOT of fuse when you are setting off more than five fireworks and it gets downright funky when it’s over ten.

The professional level (Class B) have a higher burst arc and faster climb rate/radius etc Alot of our stuff is close to ground level and having alot of exposed fuse makes for a bad show and some safety issues.

Squibs are good, but they are both unavailable to me and a bit expensive for a lafge effect.

I stand corrected… They have quick fuse…

hmm…

I might get away with building a sheild and running the fuse under it. I’d still like the ability to ignite at the flip of a switch but I’ll look into this. Thank you.

Crazeyal wrote

Um, what I suggested above will do exactly what you’re after. just get some nichrome wire (a couple inches per fuse, a big lantern battery, a push button, and some well insulated wire. hook the whole lot of it up in serial. wrap the nichrome wire around each fuse you want to light, have the kids do a countdown, and push the button. You can even be some distance away if you get some good length wire, so it’s safe to let little ones fire them off.

Google “nichrome wire”.

Screw that. It’s much easier to just get some small flashlight bulbs, say about 6 V, and carefully crack off the glass envelope. They’ll burn very hot, and will self-extinguish in a fraction of a second. The filament is very fragile, so some care in handling and setup is necessary.

If you were going to use the lightbulb idea you could just use a model ricket igniter. It is cheaper, more effective, and more robust.

Q.E.D. wrote

Guess it depends on your definition of “much easier”. Doesn’t sound easy at all to me. Maybe if you are going to only set one or two off. It’s likely effective though.

[QUOTE=Bill HGuess it depends on your definition of “much easier”. Doesn’t sound easy at all to me. Maybe if you are going to only set one or two off. It’s likely effective though.[/QUOTE]

Once you’ve had some practice cracking off the bulbs, it goes pretty quickly. And it’s failry cheap. Most places that sell Nichrome require either a minimum purchase or only sell in bulk. The bulbs, on the other hand, are readily available locally. I’ve used these in the past to set off a decent quantity of small fireworks.

I have made squibs out of the springy steel wool - not the fine stuff, the shiny lathe waste.

Just heat it with a flame to take the spring out (austentise?) and you can use it just like nichrome. Not as effective as nichrome - uses more current - but easy to find.

Wouldn’t you want them wired in parallel so the first one to go doesn’t short the whole circuit? The nichrome wire is going to heat up and fail, not just heat up, right? At least that’s my experience with using plain nichrome wire as rocket igniters, and two seemingly identical pieces of wire won’t fail at exactly the same time when wired in series.

Nichrome wire is made for cutting foam cores. It isn’t supposed to fail but you need a variable voltage power supply to make sure it’s hot enough but doesn’t fail. I vote for rocket igniters wired in parallel. Just make sure your battery can supply enough current.