Will this work - fireworks ignitor schematics - Page 1
Forum section: electronics / beginners

author: newtothis
author_rank: Contributor
timestamp: January 20, 2015, 09:18:00 pm
content: Hello everybody,This is an update (25 jan.) I found my answer elsewhere, but I will post it here for other interested parties.Thanks to all that tried to help me.schematic is appended - I try to remember to post a Picture of the reallife model, when I get the missing components and make it - maybe even a youtube demonstration.I errorneously thought that the max output of a AA battery was 2A, but it turns out that you can Draw much more (20A has been reported!)- offcourse you need to ensure the battery doesn't overheat - this is not a problem with this design as it only are used for 2 sec and the Draw is only increased to 3A.My math on the capacitor wasn't wrong so I have removed the capacitor - unfortunately this Means that the ignitor cannot be expanded to fire more fireworks simultaneously as planned - so far the only answer is a larger power supply. or strip a disposable camera (http://www.instructables.com/id/Not-your-ordinary-electronic-detonatorWith-Altoid/) - I'm not sure this Works solely by the large capacitor - or because the wires are very thin.I decreased the nichrome lenght from 10cm to 5cm (1/3feet - 1/6feet) this lowered the resistance with 5ohm (I have seen fuses pierced with wire into the BP core, where the total length is less than an 1/3 inch decreasing resistance to 0,5Ohm this could be used to increase simultaneously capacity - but not something I'm going to consider as it seems brittle and prone to errors.)purpose of the schematics (is attached)The ignitor needs a LED diode that light up (D1) when power is ON (s2). I use 2 seriel AA as a power source.The voltage will be stepped up (T1 - step up module/chip up to 7VV).The system is armed with second switch (S1).R3 and R4 represents 2* 90ft wires connecting (total of 2ohms)to a nichrome wire (R2~5hm).so a system that is ON and armed can heat up the nichrome wire and ignite the fuse when S1 is pressed (2 seconds should be enough)so total resistance is around 7ohms (there is a slight increase of the nichromewire as temp increases)Voltage is 7VVAmps needed is 1A across the nichrome wire.(Nichrome Data)http://hotwirefoamcutterinfo.com/_NiChromeData.html

author: IanB
author_rank: Super Contributor
timestamp: January 20, 2015, 09:29:17 pm
content: Please don't try and do this.Not only might you cause harm to yourself and others, you might also find yourself on the wrong side of the law if anyone does get injured.Leave fireworks to the professionals, or light home fireworks by hand with a match--it is much safer that way.

author: newtothis
author_rank: Contributor
timestamp: January 20, 2015, 09:54:13 pm
content: Thank you for taking your time to answer.And while I can appreciate your concern I would prefer we skipped the morale lecture as you have gotten the wrong idea of the purpose of this detonator.but for your ease of mind this is a fuse ignitor not a detonater despite its name. and it is most certainly not going to be used for homemade fireworks - or other illegal fireworksbut thanks the same

author: Andy Watson
author_rank: Super Contributor
timestamp: January 20, 2015, 10:01:43 pm
content: Look up "electric match" and in particular look at the rocketry websites. Somewhere on this site is all the information you need to use them.http://aeroconsystems.com/

author: apelly
author_rank: Unknown
timestamp: January 20, 2015, 10:32:16 pm
content: Where do you attach the cell phone?

author: AG6QR
author_rank: Frequent Contributor
timestamp: January 20, 2015, 11:35:56 pm
content: A transformer won't step up a DC voltage.You have no current-limiting resistor on your LEDs D1 or D2, so they will burn out when voltage is applied to them (but voltage won't be applied to D2 because the transistor won't turn on).Your capacitor is apparently expecting a DC voltage out of the transformer, which it won't see.The primary and secondary sides of the transformer are not connected, except through the transistor. The transistor's emitter and collector are connected to the primary side, and the base is connected to the secondary side, but there is no other connection to establish a common reference voltage between the two sides. With no return path, current can't flow through the base.

author: Nerull
author_rank: Frequent Contributor
timestamp: January 20, 2015, 11:47:25 pm
content: Quote from: newtothis on January 20, 2015, 09:18:00 pmhttp://www.pratt-hobbies.com/proddetail.asp?prod=GO-12Simple is best for these sorts of things, don't overcomplicate it. EMatches are much lower current and much more reliable than nichrome ignitors but are not as cheap and can be easily set off accidentally if you do any sort of continuity check without properly designing it to handle them.You will never get a 9v battery to last more than a few uses. They die rapidly in this kind of application. They are commonly used for onboard electronics activated pyro charges in high power rockets and many people refuse to use them for more than one flight.

author: Evil Lurker
author_rank: Regular Contributor
timestamp: January 20, 2015, 11:56:03 pm
content: You don't need all that fancy stuff. Just use three or four 9v batteries in series, a push button switch, and size your nichrome wire accordingly for the proper amount of resistance to regulate the current flowing though it.

author: AG6QR
author_rank: Frequent Contributor
timestamp: January 21, 2015, 12:02:02 am
content: Quote from: IanB on January 20, 2015, 09:29:17 pmI don't think so. Granted, using a bodged-up electrical ignition system has opportunities for danger, but a match isn't safe, either.A properly designed electrical system, used properly, is safer than a match, because it allows you to ignite the fireworks with nobody nearby. Fuses have unpredictable delays, and if a person is required to be near the fuse to light it, there's no guarantee he'll be able to get away before it goes off. One of the characteristics of a properly designed electrical system, used properly, is that there is an interlock to prevent the accidental application of power while a human is near the launch pad.I believe the only reason fuses are commonly used on cheap fireworks is because fuses are a lot cheaper than electrical ignition.There is a lot of similarity between fireworks and toy model rockets. The model rocketry safety code requires electrical ignition, because it's safer that way. What would make fireworks be the opposite?http://www.nar.org/safety-information/model-rocket-safety-code/Fireworks are very dangerous. They're illegal to use without a license in many jurisdictions, and they cause many injuries, including amputated digits, hearing loss, and burns. I'd recommend staying away from them entirely. But if someone won't follow that advice, at least follow all local laws and regulations.

author: IanB
author_rank: Super Contributor
timestamp: January 21, 2015, 12:17:03 am
content: Quote from: AG6QR on January 21, 2015, 12:02:02 amThis is what I was driving at. Nothing about the top post in this thread gives any suggestion of a properly designed system or consideration of interlocks. The danger inherent in a remote firing system if not properly designed is the possibility of ignition occurring with somebody nearby who isnot expecting it.If you light with a match you can:(a) tell others to keep away(b) ensure the site is clear before proceeding(c) observe proper safety precautions on your own behalf(d) avoid unintended ignitionI think a match is safer than a bodged up and badly designed remote firing system.

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 21, 2015, 02:00:39 am
content: Quote from: apelly on January 20, 2015, 10:32:16 pmi think i got the idea. please dont troll such an idea, people start speculating here.Quote from: IanB on January 21, 2015, 12:17:03 amagree. i think a well designed remote firing with warning siren etc thereof is much safer than both. i've seen body parts in pieces try to match up a bodged up and badly calculated (or not even calculated) fuse length and firework's firepower. BOOM.

author: tautech
author_rank: Super Contributor
timestamp: January 21, 2015, 02:23:55 am
content: Quote from: apelly on January 20, 2015, 10:32:16 pmA neighbour every year at guy fawkes used to fill a bag with a oxy plant mix with a short length of fuse wire and a LONG lead to a car battery.BOOMLast one they did, I was driving 2 Kms away and nearly shit my pants.Their 70 Yr old mum always watched, but that was the last one they did as it upset a few neighbours even though we live in a rural area.Good rural fun.

author: newtothis
author_rank: Contributor
timestamp: January 21, 2015, 04:36:21 am
content: Hi and thank you for the responses,>> Andy Watson: Thank you, this ignitor is actually based on those schematics - but they usually use 12V leadbatteries or a bunch of serial connected AAs, which is what I try to avoid. So I realise this makes a simple job more complicated - but I also learn more>> AG6QR: I might have put in the wrong symbol - but it is there to indicate and increase in DC, but I plan to use a DC-DC step up module so DC voltage will be Applied and flow established. I'm aware of the lacking resistors, but thank you for pointing it out.Thank you for the friendly warning.Shouldnt a PNP transistor allow flow when the base voltage becomes 0, allowing the 9V to light up the diode? If it isnt so would you care to propose a correction?>> Nerull: Thank you I know this overly complicated and as such a Little silly - but that was makes it interesting, I will consider switch the powersource to 4AAs - and this setup is actually made (by 1A) so it should also be able to use Ematches - but I'm unsure if they are regulated in my country so it is initially going to be nichrome wire.>> evil Lurker: yes offcourse - but I would like to make this design for the added learning.>> IanB: I think you are a Little hard on my system, I am afterall here to remedy any errors. safety was actually my first concern - Would'nt you consider 3 seperate switched and connecting of the wires interlock mechanismes - this is a clone of the standard pyrotechnician detonator - except I have the voltage boost/capacitor insert. I don't ever think any Ematches or the like are supposed to be connected to a turned ON and armed detonator before added to the fuse, so untill assembly they are inert, I'm not going to assemble and arm the detonator before I'm ready to detonate atleast, so even If I really screwed up I will be nowhere near at detonation (And I'm going to test the system before use offcourse..) - I don't think there are any additional benefits to the match, but if you have seen any flaws in the system please point them out.Anyhow thank you taking your time to respond, but I really would appreciate if anyone could provide the answers to the toppost, and of we could limit safety advice to practical application for the project.I realise that the use of the Word detonator instead of ignitor may have caused people to get the wrong idea - but English is my second language so I didn't think so much about it at the time

author: Psi
author_rank: Super Contributor
timestamp: January 21, 2015, 05:29:20 am
content: Model rocket igniters should do what you want.

author: MattSR
author_rank: Regular Contributor
timestamp: January 21, 2015, 06:11:16 am
content: Quote from: tautech on January 21, 2015, 02:23:55 amWhat on earth is an oxy plant mix?

author: tautech
author_rank: Super Contributor
timestamp: January 21, 2015, 07:21:10 am
content: Quote from: MattSR on January 21, 2015, 06:11:16 amNot wanting to give too much awayfor fear of somebody damaging themselves or property.Gas welding set.That's all I should say.

author: apelly
author_rank: Unknown
timestamp: January 21, 2015, 01:08:56 pm
content: I have experienced oxy acetylene employed this way. To say it is impressive is to employ humorous understatement!

author: max_torque
author_rank: Super Contributor
timestamp: January 21, 2015, 01:44:54 pm
content: For what it's worth, i think a remote electrical system is "safer" than a match, with the assumption it's done right!What i'd want to see as a minimum:1) A single mechanical "KEY" is used to "SAFE" the system. Only one key should exist, and needs to be physically tied to the person who is installing the ignitor/trigger in the pyro device. That way, no one can fire the system by mistake when that person is close to the pyro.2) When the system is "SAFE" the output terminals are actively, and mechanically "CLAMPED at low impedance" together to prevent any potential difference between them3) Firing should require two inputs; ARM & FIRE, at least one of which should be a physically difficult to move switch, such as a mechanically interlocked toggle switch. That way, the device is unlikely to fire in the event of being dropped, stood on, etc!4) Any "wiring check" low output current, should be carefully considered, and only connected when the system is ARMED.5) The user needs to carefully consider the correct operational steps and stages to ensure safe useage, for example, trigger wires should be conected to the firing device first, so that they are forced to zero potential before being connected to the pyro trigger, and the pyro trigger should be connected to the firing device wires BEFORE being inserted in the test rocket etc (so accidental fires only set off the trigger, and NOT the rocket!)One option of the mechanical KEY is to use something like a dual 4mm bananna plug socket, where the pins must be fully inserted to reach down and push open the output terminal zero ohm clamp etc. In all cases, consideration must be given to static charges and provide them a route to earth away from the pyro trigger outputs.(Generally, with restive triggering systems, static charges will not contain enough energy to fire the device, as it must physically heat up a metal coil of wire to ignition temp)

author: AG6QR
author_rank: Frequent Contributor
timestamp: January 21, 2015, 05:52:00 pm
content: Quote from: newtothis on January 21, 2015, 04:36:21 amOK, if I assume that device you've denoted with a transformer symbol isn't a transformer, but is instead some sort of packaged DC-DC converter, the transistor still won't do what you want it to do. Assuming the DC-DC converter is isolated, there's no connection from the primary side to the secondary side. Electricity flows in a circuit, meaning it's got to have a path all the way around, but the only connection from the primary side to secondary side is through the base of the transistor.If the DC-DC converter is wired with a common ground, that is, the primary ground is connected to the secondary ground inside the converter somewhere, then the base of the transistor will always be at ground voltage, and the transistor will always be on. Except that there's nothing to limit current through the base, so the transistor will burn out from overcurrent as soon as S1 is first closed.If the DC-DC converter is wired with a common + rail instead of a common ground, then the base may become far more negative than either the emitter or collector, in addition to the problem with no current limit.This is a minor point, but generally, NPN transistors work a little better than PNP. Don't be afraid to use PNP when there's a reason to do so, but when a circuit can be equally well constructed using NPN or PNP, it's usually best to use NPN. It probably doesn't matter so much in this situation, though.For the reasons why NPN is generally preferred, seehttp://www.madsci.org/posts/archives/2003-05/1051807147.Ph.r.htmlOh, and on a completely unrelated subject, pay attention to max_torque's good advice regarding interlock systems. Being safe involves both a safe design, and a safe protocol for usage.

author: tautech
author_rank: Super Contributor
timestamp: January 21, 2015, 05:59:38 pm
content: Quote from: apelly on January 21, 2015, 01:08:56 pmShhhhhThose are the words I was trying not to reveal.

author: Nerull
author_rank: Frequent Contributor
timestamp: January 22, 2015, 05:01:59 am
content: You need to be very careful when using transistors/mosfets or even relays (Which can weld their contacts together) to switch current in a system like this. You have to consider the possibly of failure, and what happens if it fails and what you can do to reduce the risk. There has been more than one instance of launch systems at rocketry clubs failing closed and firing ignitors as soon as they are hooked up, and people needing to jump out of the way as their rocket launches on its own accord. You don't want that to happen with a firework. An interlock that can completely disconnect the battery from the circuit is a start. Things like loud buzzers on the output to provide an audible alert of live leads are good too.

author: zapta
author_rank: Super Contributor
timestamp: January 22, 2015, 04:59:13 pm
content: Quote from: apelly on January 20, 2015, 10:32:16 pmA manual switch on the body belt should do.

author: MFX
author_rank: Regular Contributor
timestamp: January 22, 2015, 05:47:37 pm
content: I'm not going to go all nanny state on you and say don't build a firing system but I would say you need to learn a lot more before you can do it safely. Start simple, in most cases there is simply no need for DC-DC converters, capacitor discharge units are only used when you have a large number of igniters to fire at once, unless of course you're intending to make your own "e matches" from resistors? 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).

author: MFX
author_rank: Regular Contributor
timestamp: January 22, 2015, 05:55:59 pm
content: Quote from: max_torque on January 21, 2015, 01:44:54 pmJust to add I use captive key switches where the key can only be removed in the safe position. Test current (I use 5 to 10mA) should be provided by a fusible resistor at a minimum and tests should be treated as if you were live firing, no people on site.

author: zapta
author_rank: Super Contributor
timestamp: January 22, 2015, 06:01:02 pm
content: Quote from: MFX on January 22, 2015, 05:47:37 pmThis is what they always say.Be careful.

author: Falcon69
author_rank: Super Contributor
timestamp: January 22, 2015, 06:28:15 pm
content: 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.

author: MFX
author_rank: Regular Contributor
timestamp: January 22, 2015, 07:37:28 pm
content: Quote from: Richard Crowley on January 22, 2015, 07:00:48 pmActually 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.

author: MFX
author_rank: Regular Contributor
timestamp: January 22, 2015, 07:44:51 pm
content: Quote from: zapta on January 22, 2015, 06:01:02 pmI 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 :-

author: IanB
author_rank: Super Contributor
timestamp: January 22, 2015, 09:56:33 pm
content: Quote from: MFX on January 22, 2015, 07:37:28 pmThe 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?

author: MFX
author_rank: Regular Contributor
timestamp: January 22, 2015, 11:01:34 pm
content: Quote from: IanB on January 22, 2015, 09:56:33 pmYes 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.

author: Nerull
author_rank: Frequent Contributor
timestamp: January 23, 2015, 03:25:48 am
content: 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.

author: IanB
author_rank: Super Contributor
timestamp: January 23, 2015, 03:48:48 am
content: Quote from: Nerull on January 23, 2015, 03:25:48 amYou mean like this?http://youtu.be/ndVhgq1yHdA

author: MFX
author_rank: Regular Contributor
timestamp: January 23, 2015, 12:55:28 pm
content: Quote from: Nerull on January 23, 2015, 03:25:48 amSite 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.

author: newtothis
author_rank: Contributor
timestamp: January 25, 2015, 08:32:59 am
content: 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 subjectEspecially 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

author: LukeW
author_rank: Frequent Contributor
timestamp: January 25, 2015, 01:39:52 pm
content: http://altusmetrum.org/TeleMetrum/v2.0/telemetrum-sch.pdfHave 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.

author: MFX
author_rank: Regular Contributor
timestamp: January 25, 2015, 01:51:58 pm
content: Quote from: newtothis on January 25, 2015, 08:32:59 amStill 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.

author: newtothis
author_rank: Contributor
timestamp: January 25, 2015, 04:11:20 pm
content: >> MFXYou 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 LukeWI 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.

author: MFX
author_rank: Regular Contributor
timestamp: January 25, 2015, 06:06:34 pm
content: 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.