In recent Fireworks Tips articles I’ve discussed making electric matches with which to ignite fireworks electrically, and the construction of Cremora fireballs which can be impressive additions to any show.
I’ve also looked at the issues involved in thoroughly planning a consumer fireworks display.
Now it’s time to discuss using those electric matches in conjunction with an electric firing system and shooting wire, and hooking fireworks devices up to them out in the field.
In the next article, I’ll also show you how to use visco fuse, fast-visco fuse, quickmatch, time fuse, and fast-fuse to attach fireworks devices to each other for sequential firing.
Using these methods together can result in a nicely timed display, and will also enable you, the display designer, to sit back and enjoy the show with the rest of the crowd.
“Scab wire” or shooting wire is the wire that is used to connect the firing panel to the electric match. It essentially extends the length of the leads of the electric match, or connects multiple igniters in one firing circuit. It is important to know the wire’s resistance for a known length of it.
Scab wire usually comes in rolls that have “duplex” wire on them, which means that the wire is two-conductor wire. Two insulated wires are attached to each other, side-by-side.
Two-conductor, copper, 22-gauge, yellow-insulation wire is probably the most commonly found scab wire out in the field. There is also copper-clad, aluminum, orange-insulation wire that is being imported and used.
I cut the wire with the wire-cutters (dykes), split the insulated wires apart with the same tool, or the razor knife, or with my fingernails, and strip the insulation with the dykes or with my fingernails. If I use the dykes to strip the insulation, I’m careful to avoid damaging the wire itself, which is easy to do. I therefore prefer to strip the insulation with my fingernails.
The most important thing to know about the wire that you are using is its resistance. This is listed as “ohms per 1000 feet” in wire data tables. It’s easy to determine this for yourself, though.
All you need is the wire and a multimeter, which measures voltage and resistance. A digital meter like the one on the left is a good investment because it will be used in this step and also in future testing of firing circuits. The analog meter on the right is good for testing batteries and can be used to check resistance, but it is not as accurate as the digital meter.
Note: In a circuit which contains electric matches, I only use the digital meter to check resistance. The analog meter can fire ematches, which is NOT something you want to happen!
To determine the resistance of my shooting wire, I take 50 feet of my duplex (two conductor) wire, bare 1 inch of both wires at one end of it, and twist those ends together securely. I then separate the wires at the other end for 3-4 inches, and bare 1 inch of those ends. Now I set the dial on the multimeter to the setting for measuring resistance (ohms) and wrap one bared end of the shooting wire on one of the meter’s probes, and the other end of the wire on the other probe.
I’m actually measuring the resistance in 100 feet of the single-strand wire since the measurement current is going out 50 feet to the twisted ends, and then back 50 feet to the meter.
I should get a reading between 1.6 ohms for the 22 gauge copper wire, and 3 ohms for the copper clad aluminum wire. This exact reading will depend on the actual wire you are using. I then multiply this reading by 10 to get the resistance in ohms per 1000 feet of the wire.
The yellow wire I’ve described has a resistance of 16 ohms per 1000 feet, and the orange wire’s resistance is about 30 ohms per 1000 feet.
I have a few different firing systems. I have a new Skylighter 12 cue wireless firing system (GN6020) which puts out 4.5 volts. Then there are my older model 8 and 12 cue wireless panels which put out 12 and 18 volts. I also have a hard-wired 144 cue firing system which sends out 24 volts, and I’ve recently seen the 10 cue capacitive discharge, hard-wired firing system (GN6011) at Skylighter which fires with higher voltages.