Will this work - fireworks ignitor schematics

[Falcon69]

This thread reminds me of the old Redneck saying, "Hey Ya'll, watch this!"

But, I am interested in this thread, as every 4th of July, we have a massive party and we try and set the fireworks off together.  The big ones that shoot up in the air and ignite into a cluster of lights. We try and line them all up in like 10 of them to go off at the same time.  We usually can't light them fast enough, or they start to go off before we can light them all. This results in ringing in the ears, of course. we even had one fall over, but we fixed that problem by making a custom stand with tubes to launch them all.

Having an electronic ignition, detonator, whatever you want to call it, to ignite all the fuses at the same time, would actually be safer to do this, then getting close and trying to light all those fuses at the same time with  a match/lighter/propane torch.

I'd be very interested in a working electronic means to do this.

Regardless of what people say *cough* IanB *cough*, people are going to do it whether it is safe or not. If they ask for help, why not offer up your expertize to help them make the situation safer? After-all, they are going to attempt it anyway.

IMOI, for my situation, having an electronic ignition will be MUCH safer.

[MFX]

If you look at what the professionals use (the people that do massive public pyrotechnic shows), it is remarkably primitive and simple.
But that is also what gives it high reliability and excellent safety.

Using an inadequate cell and voltage booster is probably the LEAST appropriate way to do this.
If you know what power you have available (even if it is only one AA cell or one 9V battery),
then design the detonators for the voltage and current available. and use a simple switch.
A mechanical switch, or a relay, or a transistor, or whatever.

Actually modern systems are FAR from primitive and simple. Most large shows are fired by computer controlled firing systems such as fire one or Pytotronix PTX (But there are LOADS more), most have wireless firing options and some use GPS for synchronised timing. MOSFETS are most commonly used with the safest systems using high and low side MOSFETS. As with anything the more complex you get the more you have to compromise on safety it's almost impossible to make anything truly "fail safe" these days there is always some element of risk but that is minimised as much as possible. Common sense site procedures also apply, i.e. all crew to be off site before the firing desk is connected and switched on.

[MFX]

BTW I have recently designed a completely self testing high side/low side firing system output stage, there would need to be a minimum of three catastrophic failures in the electronics (one of those being a fusable resistor going short circuit which is  pretty much unheard of).

This is what they always say.

Be careful.

I get paid to do this and am always careful. You can't eliminate all risk but you can minimise it. My showreel BTW just to show I'm not an amateur at this :-

[IanB]

most have wireless firing options

The idea of wireless control is really scary and horrifying. To be secure, the system would need a digitally encrypted data channel with unique private keys per installation, and would be required to successfully decrypt a command message on the incoming channel before activating. Do such systems actually have this level of security?

[MFX]

most have wireless firing options

The idea of wireless control is really scary and horrifying. To be secure, the system would need a digitally encrypted data channel with unique private keys per installation, and would be required to successfully decrypt a command message on the incoming channel before activating. Do such systems actually have this level of security?

Yes they generally have a system codes and encryption but given the transient nature of such systems they're not really a viable malicious hacker target or likely to get triggered by another nearby system of the same make. Most sensible pyro companies will avoid wireless wherever possible but there are some shows where wired simply isn't an option. On the London new years eve display there are multiple firing systems on barges on the Thames, on the London eye and on land, cabling between them and front of house would be impractical, they don't use wireless between the systems as such but all of the systems have the show pre programmed and are all triggered by a GPS receiver on the stroke of midnight. Someone with a high power GPS jammer could possibly stop the show from firing but it would take some pretty specialist kit to maliciously fire the show.

[Nerull]

I would also hope that these systems are designed such that once the system is armed the worst than can happen from a premature firing is one really spectacular volley and a ruined show. The largest fireworks display in the US is fired from eight 400 ft. barges and one highway bridge firing 50,000+ shells. The show is all synchronized, but I'm not sure on exactly how they do it.

[IanB]

I would also hope that these systems are designed such that once the system is armed the worst than can happen from a premature firing is one really spectacular volley and a ruined show.

You mean like this?

http://youtu.be/ndVhgq1yHdA

[MFX]

I would also hope that these systems are designed such that once the system is armed the worst than can happen from a premature firing is one really spectacular volley and a ruined show.

Site layout is important from that respect particularly to ensure shells can't collide if they inadvertently fire out of sequence. Several of the spectacular cock ups weren't due to hardware faults but human error in programming the show, accidentally using frames instead of seconds for example.

[newtothis]

Hello everybody,

I've been busy in real life, so sorry for the late reply, but thank you for contributing to the post, even though I think it strayed quite alot from the intended subject
Especially thanks to thoose who tried to answer my questions.

I have made some more research, and conferred at another forum and found the answers.

I have added the new information to the top post/initial post - so it is easy to find for other interessted parties

[LukeW]

http://altusmetrum.org/TeleMetrum/v2.0/telemetrum-sch.pdf

Have a look at the schematic here, particularly the electric match FET open-drain outputs at lower left.

Note that a couple of resistors are used in parallel with the FET, fairly large resistors, which bias a tiny amount of current through the electric match.

This provides a "sense" output which allows you to measure continuity in the igniter - the bridgewire should normally have a very low resistance, which means that output will be high only with bridgewire continuity, so you can detect a faulty igniter or broken wire before it has to fire.

This current needs to be set at a level that is certainly known to be safe for the pyrotechnic device that you're using.

Then again, this sort of thing is probably more important where you need a reliable electroexplosive device to separate the recovery parachutes on your rocket, or something like that, and it's not so important for display fireworks - but it can't hurt.

[MFX]

Hello everybody,

I've been busy in real life, so sorry for the late reply, but thank you for contributing to the post, even though I think it strayed quite alot from the intended subject
Especially thanks to thoose who tried to answer my questions.

I have made some more research, and conferred at another forum and found the answers.

I have added the new information to the top post/initial post - so it is easy to find for other interessted parties

Still think you're going about this wrong. The igniter should be designed for around 1 to 2 Ohm resistance/ 0.5 to 1 Amp firing current (With a no fire current of 0.3 Amps, this is around the spec. of commercial igniters (there is some variation) and easy to achieve with home made ones, in that case 2AA's would easily fire three igniters without the need for a converter. For simple capactitor discharge firing a modified camera flash will work well particularly with insensitive igniters purely because of the amount of energy the capacitor is dumping through the igniter wires, they won't just be getting hot but virtually exploding.

[newtothis]

>> MFX
You are offcourse right,  I'm going to make my own ignitor with Nichrome wire and I'm going to use 36gauge and 1/6 of a feet and thats about 5ohm - this could be done with thinner/shorter wire lowering the resitance/needed current to the Commercial scale as you also say - but I read somewhere that above 36G the wire are prone to breakage and I really want to just make a ultra simple Fuse by twisting the wire around a firework-fuse and connect it to my 2 90 feets wires with alligator clips.

The transformer was initially added, because a single AA battery contains enough power to light several hundred fuses even at the most pessimistic calculations, but I only expect to use it 1-10 times a year - so adding even more batteries would be an extreme Waste of energy, and I had a DC-DC converter in spare. You make an excellent argument as to why it can be skipped, but I'm kinda hooked on the idea of making a high power unit is easier than fiddle with low res/current fuses, but the one used on new years eve might turnout to be without a converter.

>> MFX and LukeW
I believe a secondary wire from the 2AA with a 50 ohm resistor through the fuse to light up a diode should be a efficient Circuit control without igniting the fuse (22mA shouldn't cause any significant temperature increase and I will probably add one - but this will be tested when i have the nichrome. (It offcourse needs to Work only when system is armed - just in case)

I'm actually very glad you commented on the capacitor discharge - now it makes sense to me how he succeds by one AA.

[MFX]

A thing to watch then if you have no primer on your igniters is that Visco fuse used on consumer fireworks is hard to light (even commercial igniter have trouble as they are too fast) so you would need the wire to get hot for a significant amount of time, so you wouldn't want cap discharge as that will blow the wire apart before the fuse has a chance to ignite. Personally I'd either go for a small lead acid battery to supply the current you need (or maybe a bunch of NiCd's/NiMh) or look at improving the igniter design. You can SAFELY make a simple slow burning primer from ground up safety match heads made into a thick paste with a tiny amount of water and left to dry in a WARM place) I won't go any more into igniter primers here as it going too off topic but there's plenty of info around, just be safe. If you do get into mixing chemicals only make small batches at a time.