Igniting a Programmed Fireworks Display?

seg9585 asks: "I am interested in setting up a programmable fireworks display this New Years, and I was wondering if anyone from the Slashdot community had any advice as to how to set one up easily, inexpensively, and safely by someone with little experience with electronics/wiring. I do have a VEX controller which I can use for digital output, but I would rather not have to buy a ton of relays and create a spark by just shorting out the circuit. Is there a better way to do this?"

Comments

Get a professional

[caffeinatedOnline]

I had a friend who was a professional pyrotechnic for many years. On a job for a small new years eve festival something went wrong with the setup and he was killed. This was someone who had years of experience doing this, and was working with a group of other people who had been doing it for years. If you really don't know exactly what you are doing, the chance of you not only hurting/killing yourself, but others is there.

No LEUP? Use rocketry ignitors and MOSFETs.

[Chembal]

I tackled this same problem several times with varying results.

My first attempt used a TINI controller board hooked up to relays hooked up to model rocket igniters. This worked well, but relays are expensive and don't scale well if you want to do this on the cheap.

My next attempt used a Freescale GP32 controller with MOSFETs. This worked very well, and is a more scalable solution. Again, I used model rocket igniters. If you look at my pictures, you can see how I made a nice set of firing racks, too, complete with power distribution scheme and chainable serial control. I wrote a program in Java to send control signals to the controllers to shoot the shells off in sequence.

After these attempts, I finally got sick of playing with the small stuff and got my explosives permit so I can play with 1.3g display fireworks. When you have your explosives permit, you're no longer limited to crappy model rocket igniters. You can buy professional quality e-matches that are meant for the task. They're a bit pricey, but they already are the right length of leads, and work GREAT. Also, the larger shells are MUCH easier to electrically fuse, since they use quick match instead of visco fuse. But, no vendor is going to sell you those nice e-matches without first seeing your LEUP. (Low Explosives User Permit.) That takes a bit of work to get, so I'll assume that's beyond your scope. Of course, there are also professional systems available for control, but they're pricey.

So, I'm going to take a guess that you don't have a LEUP and just want to hack something together to shoot off your 1.4g consumer fireworks. Here's what I've learned from my experience doing the same thing. It's not that tough to do, but don't underestimate the amount of wiring you have ahead of you if you intend on shooting off more than a few shells. With only a few weeks from new years, you'll probably get a more impressive display by buying several nice cakes. But, since that's not the slashdot way, here's how you can do what you want to do...

• First, don't do any of this in your living room! Don't go burning down or blowing up your house.
• Buy packs of estes model rocket igniters, and attach longer leads to them. This is the cheapest and most reliable way of doing what you want without getting an explosives permit.
• Buy the plain-jane 1.4g artillery shells from your favorite roadside vendor (NOT the canister style shells, because they're not easily electrically re-fused), and CAREFULLY cut or remove the fuses. Black powder is sensitive stuff, so be smart about this step!!!
• Cut a slit in the paper bottom of the shell. This is where the black powder lift charge is. Insert your igniter into the slit, and tape over it and any hole left over from the original fuse to hold the igniter in place and prevent the loss of your lift charge.
• Place the shells into your PROPERLY SIZED artillery shell tubes, and hook up the leads to your firing system, be that through relays, MOSFETs, or a simple switch. I can't emphasize enough how important it is to get the right size and type of tubes and to make sure they are stable! Pyro Universe is a good resource for this and other info.
• When everyone is a safe distance away, and the area is secure, hook up your system to power and apply current to the igniters. They will fire the instant you apply current if you've inserted the igniter correctly.

Please be safe about this! It's a ton of fun, but observe sensible safety precautions. I highly recommend taking a class on display fireworks to learn how to do all this right. Premier Pyro gives great classes on this every year, and you'll have tons of fun to boot. At the very least, give NFPA 11