A brief foray into explosions

Every year, myself, my family and some friends get together on New Year’s Eve, have a lovely meal and at midnight, let off the obligatory fireworks. Their house is surrounded by farmland so we have a huge amount of space, making operation of larger fireworks possible, but we’ve in past years stuck to firing the larger end of garden fireworks (category 2).

This year, tired of the inevitable mucking around with unreliable gas lighters at midnight, we decided to take a look at electronic ignition systems and upgrade to category 3 “display” fireworks.

We picked up a 12 cue electronic firing system from Wireless Fireworks, who kindly got next-day delivery sorted out on zero notice so we could get everything before NYE. We also grabbed a box of 50 Talon igniters with 4 metre cables, to let us wire the whole display (which ended up only using ~20 igniters, so we have some for next time). As well as being wireless the main advantage of this box over the cheaper/distributed ones (in my mind at least) was that it had a continuity test function, along with a real keyed safety switch – which is a requirement if you ask me. The labelling leaves a lot to be desired – I’ve modified ours so the safety switch is labelled “SAFE” and “ARM” instead of the ambiguous “OFF” and “ON” (safety on = safe? Nope! Safety on = armed…).

The Talon igniters are just bits of fuse wire and a well-designed clip. They clip onto the green/pink fuses you’ll find on any cat2/3 firework and just get very hot – the lack of pyro in the igniters is a huge plus. We had one failure out of our 18 effects which looks to have been a continuity issue. Which brings me to the box that doesn’t exist yet but someone really should make…

You might notice that I said we used 18 effects but that we only have 12 channels. The box is designed to let you pair up effects – we didn’t try more than 2 in a channel but I suspect 3 would work fine. But our one failure was one of these paired effects – probably just the connector not making a good contact with the wire for that effect. In future I plan to solder the ends together for paired effects to make a solid connection between the two fired effects, such that if any continuity check passes, it’s a pass for everything. Ideally you’d have a box that had one wire out to the main box, then two connectors for igniters with switches to let you do continuity checks per-igniter once it’s all wired.

This has all lead me to think it might be a fun project to try making a firing box of my own using the Talon igniters. All it really needs is a battery, some relays or other switches capable of handling the load, continuity test functionality and some safety mechanics around when the current-unrestricted battery connection is made, but that’s all quite straightforward – it’d be nice to have a larger system that could scale up to higher channel counts, but commercial offerings over about 12 channels are all quite expensive! The wireless functionality is nice, but I’d rather have something secure – much to my surprise, the wireless system in these firing boxes is a classic 433MHz type of the sort you’d find in remote controlled switches/mains plugs. Replacing this with WPA2 encrypted 5GHz wifi or a 433/896MHz encrypted wireless system would be nice.

Still, the end result was great – being able to let everything off within seconds of each other (and hitting midnight with a volley of big rockets) was fantastic, and while there was about 4 hours spent setting it all up, I could for the first time stand with friends and family to let everything off. Lots of fun and much safer to boot!

Of course, no fireworks post would be complete without some pictures of the end result – I tried taking my pictures this year with CHDK running on a Canon Powershot G10 with a motion detection script. It almost worked flawlessly…