My arduino powered firework sequencer. 2018 version! - Page 1
Forum section: electronics / projects

author: usagi
author_rank: Frequent Contributor
timestamp: July 01, 2018, 10:27:37 pm
content: Myprevious firework controller worked great.The 2017 show was a great success!This year, sequencer version 2!

author: usagi
author_rank: Frequent Contributor
timestamp: July 01, 2018, 10:32:27 pm
content: First, the stash!

author: usagi
author_rank: Frequent Contributor
timestamp: July 01, 2018, 10:35:20 pm
content: lasercut enclosures again. hardboard is great stuff for this.

author: usagi
author_rank: Frequent Contributor
timestamp: July 01, 2018, 10:38:00 pm
content: used jlcpcb to design a bunch of PCBs to make assembly easier this time.

author: usagi
author_rank: Frequent Contributor
timestamp: July 01, 2018, 10:45:22 pm
content: because I have to assemble 10 of them this time...

author: rstofer
author_rank: Super Contributor
timestamp: July 01, 2018, 11:54:14 pm
content: Nice project! I like the lasercutter.

author: CopperCone
author_rank: Super Contributor
timestamp: July 02, 2018, 01:08:41 am
content: man I would use steel shielding at least for something connected to explosives, that's pretty ratchet as far as applications and risks, based on the lack of metal I will assume susceptibility is not considered in the design, connected to explosives.IMO incompetent.You should also use shielded wire and RF shunts on the detonators, really they should form a conductive seal with the shield and be part of it. A small powder charge should have no problems rupturing the shielded detonator casing. This is made with speaker connectors and wood.This is something you want magnetic shielding for. Also interlocks. You should post a PCB so it can be likely fixed. The igniter wire should also be brazed to the conductor wire so you can't get a loose connection. A spark can set off powder geometries of a certain shape, so you can lower your initiation threshold from a heat requirement of the wire to a spark ignition (that is unreliable but possible). I hope you did not twist those initiators on, particularly when you have corrosive pyrotechnical compositions that likely use sulfur, chlorates, etc. The spark should not be remotely able to occur anywhere near the powder, so you want lead wires that leave the detonator and connect some where else.

author: usagi
author_rank: Frequent Contributor
timestamp: July 02, 2018, 04:08:34 am
content: Quote from: CopperCone on July 02, 2018, 01:08:41 amthese are e-matches, not "detonators".have a look at commercial firework controllers. speaker connectors and plastic are the norm in the industry.these controller boxes will be away from the fireworks by several meters. it's not like the controllers are strapped directly to the fireworks.http://www.cobrafiringsystems.com/www.acepyro.com/Shop/FiringSystems#starfirenobody uses e-matches with shielded wire. this isn't quarry blasting. brazed wire igniters? seriously? even zambelli doesn't do it.please get educated on firing systems for display fireworks.

author: CopperCone
author_rank: Super Contributor
timestamp: July 02, 2018, 04:14:07 pm
content: So what the industry is a buncha cheap incompetent fucktards what else is new?You built cheap trash that will be connected to pyrotechnics. Its a bad example of how to build something that controls something dangerous.I would use quick match and time fuse over that.Someone might get the bright idea to connect it to large salutes, gasoline fireballs or other stuff that wont just hopefully shoot up in the air if it misfires.

author: DaJMasta
author_rank: Super Contributor
timestamp: July 02, 2018, 05:56:25 pm
content: That seems awfully overblown given the small number of injuries that happen as a result of professional fireworks displays, especially due to problems with the ignition mechanism or interference with the controls. You are absolutely welcome to use safer options, but if there are thousands of displays a year using these methods with very few injuries or damaging misfires.... the industry status quo is probably sufficient. Also worth mentioning that the fire marshals are signing off on the whole setup before they're loaded into the tubes and it's absolutely the case that professional operations have to be insured - so it's also safe enough for the insurance companies to charge rates that still allow them to maintain these practices.Maybe you don't think the safety measures are sufficient, but if the professionals, the fire marshals, and the insurers do..... and the available injury data corroborates that..... that's sufficient to convince me.

author: CopperCone
author_rank: Super Contributor
timestamp: July 02, 2018, 07:09:23 pm
content: whatever man I just imagine one of those burning cultists from blood running around after someone skips procedure a bit hooking up a 20 gallon gasoline fireball or 500g flash salute at an air show or somethingI can't prevent you from doing anything now can I? I am just discouraging other people from trying to save a few bucks when dealing with seriously dangerous shit. I feel obligated to state my opinion.They are one of the most dangerous things you can buy other then fire arms and commercial explosives. Some fireworks displays use similar methodology to military improvised munitions manuals.You wanna fuck around being a cheap skate go ahead. I can tell you from experience amending anything involving fire marshals and the NFPA is like pushing diarrhea up a hill. They rarely do anything proactive and even reactive measures take forever. Try talking to someone that worked on one of their committees.

author: Yansi
author_rank: Super Contributor
timestamp: July 02, 2018, 07:53:00 pm
content: ...just wandering if the outputs are at least shorted when idle.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 03, 2018, 01:02:03 am
content: Quote from: CopperCone on July 02, 2018, 04:14:07 pm^^ Don't mind CopperCone, he's just being self-referential.Tim

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 03, 2018, 01:03:05 am
content: Quote from: Yansi on July 02, 2018, 07:53:00 pmThat, or biased to check for continuity (and no more!).IIRC from last year's thread, the design is well conceived and proven. This is just biggermoar.Tim

author: CopperCone
author_rank: Super Contributor
timestamp: July 03, 2018, 01:30:06 am
content: now that I think about it, it should be heavily sealed because it might be placed on humid grass or stored near pyrotechnical compositions. What if that sulfur is not distilled right?the thing is built with what looks to be the same materials you would put in a disposable twine tied shell as star separators lolI can actually see it happening, someone is gonna coil up a buncha sulfur oxide encrusted wires that still smells bad from the close proximity to the display, throw the box and the wires in the back of a poorly sealed box truck and its gonna be outside in the july and august humidity.

author: CopperCone
author_rank: Super Contributor
timestamp: July 03, 2018, 01:40:54 am
content: Quote from: blueskull on July 03, 2018, 01:39:02 amhave you ever seen a large gasoline fire ball go off? Or a 15 inch shell explode? Or maybe some high explosives someone had laying around to add some ground boom to a show?You can connect this thing to a fused blasting cap if you want.What do you think I am complaining about a fucking alarm clock? It's a detonator circuit.Do you think someone is gonna give a shit about class D restrictions at a private party or something?I think its just people that never experienced a close up explosion or real heat in their life talking a buncha idiotic shit in this thread.

author: usagi
author_rank: Frequent Contributor
timestamp: July 03, 2018, 04:40:39 am
content: Quote from: T3sl4co1l on July 03, 2018, 01:03:05 amyes, outputs are shunted when idle.last year's design worked very well, this is version 2.

author: CopperCone
author_rank: Super Contributor
timestamp: July 03, 2018, 06:39:36 pm
content: Quote from: blueskull on July 03, 2018, 01:51:13 amyou can put a pound of black powder in the bottom of a pale, stick a light bulb igniter in it, then put a 20 gallon bag of gasoline on top of it to make a show firework or possibly thermal weapon if you aim at at a convoy passing by, regardless they are a popular finisher for fireworks show because it looks like a stereotypical atom bomb. Also popular for movie effects where they don't want to get high explosives license etc.I don't care what compounds you made, have you ever been close to a powerful explosion or fire ? I made plenty of compounds but manufacture or small chemistry lab test burn or detonating some matchhead sized pile of crap with a hammer won't give you the same sensibilities as experiencing a thermal burn from far away or getting nailed with a shock wave.

author: usagi
author_rank: Frequent Contributor
timestamp: July 04, 2018, 03:18:21 am
content: Quote from: CopperCone on July 03, 2018, 01:40:54 am"class d"? "15 inch shell"? gasoline? high explosives? 500g flash salute? quick match with time fuse? what in the world are you blathering on about? you're just making shit up. no pyro talks like that. you have already proven you know nothing about the industry.this is 1.4g you idiot. i'm not hooking it up to blasting caps and i am not doing any of those things you are drivelling on about.stop posting, you have a terminal case of stupid. the only idiotic shit being posted in this thread is from you.

author: Nusa
author_rank: Super Contributor
timestamp: July 04, 2018, 06:35:05 am
content: Things can always go wrong, even for the professionals. In 2012 I saw the San Diego barge fireworks intended for a 17 minute show turn into a very energetic 30 second show. ALL the fireworks went off at once!

author: mikerj
author_rank: Super Contributor
timestamp: July 04, 2018, 07:02:27 am
content: Quote from: blueskull on July 03, 2018, 01:39:02 amAgreed. Sadly every forum on the internet has their share of people that are compelled to denigrate others to make themselves feel important.I'm looking forward to seeing the OP's display this year, that amount of fireworks must be a pretty big investment.

author: CopperCone
author_rank: Super Contributor
timestamp: July 04, 2018, 01:50:54 pm
content: NOTE: This message has been deleted by the forum moderator Simon for being against the forum rules and/or at the discretion of the moderator as being in the best interests of the forum community and the nature of the thread.If you believe this to be in error, please contact the moderator involved.An optional additional explanation is:

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 04, 2018, 02:19:49 pm
content: Quote from: mikerj on July 04, 2018, 07:02:27 amMe too.IMHO it is a shame this thread has got out of hand with lots of shouty stuff. The OP is evolving their design and assuming they aren't incinerated today they are likely to be able to incorporate some of the suggestions next year.

author: Simon
author_rank: Unknown
timestamp: July 04, 2018, 02:53:04 pm
content: Calm down coppercone!

author: Zero999
author_rank: Super Contributor
timestamp: July 04, 2018, 03:27:29 pm
content: Quote from: Nusa on July 04, 2018, 06:35:05 amWho was killed or injured, due to that incident?This isn't safety critical. As long as the area is clear, before the power is connected, there's no risk of anyone being hurt, due to it misfiring.

author: CopperCone
author_rank: Super Contributor
timestamp: July 04, 2018, 04:07:50 pm
content: you can have a static charge occur between the igniter wire and the earth. Should not happen because of insulators but charcoal and metal powders are conductive and you have moisture. You need to ensure there is a favorable area for a spark to form away from the powder charge chamber. Only posted because it's not obvious and relates to why metal/shield design is a good idea. Or a spark occur on a broke igniter wire, they are usually thin or very fragile if you are 'smart' enough to use a light bulb.

author: stj
author_rank: Super Contributor
timestamp: July 04, 2018, 04:36:34 pm
content: it's obvious most people here dont know electric matches are a virtual shortcircuit and need a MINIMUM 0f half an amp to fire - usually atleast double that to be sure it will go.they arent like airbag triggers - they cant be fired by static.

author: CopperCone
author_rank: Super Contributor
timestamp: July 04, 2018, 04:50:39 pm
content: Quote from: stj on July 04, 2018, 04:36:34 pmits well known that they are surrounded by a conductive powder. It's also obvious that if you beak the wire a spark gap forms. If the enclosure is wet or covered with powder, and touches the earth, a spark gap forms between the wires connected to the igniter and the chassis.It's also obvious that you don't need much energy to ignite a microscopic particle of carbon that has had oxidizer and sulfur beat into it by a ball mill or recrystallized inside of it.Even if you use smokeless powder or pyrodex (which has charcoal in it) its often lubricated by very fine graphite (forgoing the usual conductive charcoal black powder), though it should be more difficult to ignite so long its been polished well in a mill to break off corners that can lower ignition temperature. But transport and temperature fluctuations may cause a fracture and formation of small particles that have a drastically lower ignition behavior.

author: usagi
author_rank: Frequent Contributor
timestamp: July 04, 2018, 05:49:24 pm
content: Quote from: stj on July 04, 2018, 04:36:34 pmyep, pyrogen igniters are very robust electric firing devices -- which explains why they are used. they are very safe and reliable. the only unintentional ignition i can recall is due to direct lightning strikes on the shooting site, no real way to prevent that!nichrome igniters are also an option. you need a beefy system to ignite them though. the igniter wire is also very fragile and easy to break when fusing up.my firing system has safe defaults, multiple interlocks, and idle shunts. the system uses encrypted spread spectrum with 2-way handshaking. i even have separate i2c buses for devices, none of the buses are shared.

author: Teledog
author_rank: Regular Contributor
timestamp: July 04, 2018, 06:35:30 pm
content: Nifty stuff!Friends in the entertainment business were always using pyrotechnics for stage shows.Strange happenstance that Big Clive just did a video on the electric matches;Looked them up, and the specs do state 500mA for a single match & 800mA for series ignition.Doubt I'd ever get into it (with our nanny state laws), but interesting non-the-less!

author: CopperCone
author_rank: Super Contributor
timestamp: July 04, 2018, 10:23:25 pm
content: whats that gotta do with lightning? You clearly wrote that you don't give a shit based on your handling of pyrophoric, toxic and carcinogenic chemicals and synthesis of high explosives without safety precautions in your boxers. TNT, RDX, HMX, nitrated plastic / plasticizer fumes.. all that stuff is not great for you buddy. Do you even know the properties of nitric acid oxidized encapsulant fumes? Maybe read about effects of substances like TNT on a human.Maybe you should not be doing safety analysis ? I would not want to get TNT containing solution spilled on me. Perhaps invest in a lab coat, fume hood, goggles and a mask?

author: Dubbie
author_rank: Unknown
timestamp: July 04, 2018, 10:54:11 pm
content: Despite all your big words coppercone, it's clear you have no idea what you are talking about.You honestly sound like a raving lunatic.What the heck has TNT got to do with pyrotechnic displays?

author: KaneTW
author_rank: Frequent Contributor
timestamp: July 04, 2018, 11:04:09 pm
content: Honestly it says a lot more about your own views on safety that you infer a disregard for safety precautions from "I currently have some strong acid blend for decapping chips within arms reach, and I'm only wearing a boxer and a shirt."In arms reach, in a tightly sealed, appropriate container.Not like you'd expect anything else from a poster with a Homeland Security avatar.

author: CopperCone
author_rank: Super Contributor
timestamp: July 04, 2018, 11:54:52 pm
content: Quote from: Dubbie on July 04, 2018, 10:54:11 pmYou gotta read all the posts man, you can't understand a thread unless you read all the posts. Your post comes off like you just smoked your user name lolMaybe you need to cut down man

author: CopperCone
author_rank: Super Contributor
timestamp: July 04, 2018, 11:57:42 pm
content: Quote from: KaneTW on July 04, 2018, 11:04:09 pmDid you ever try to store fuming white nitric acid? It tends to gas through seals. I hope you got some wax on those seals. I would recommend storing that in a fume hood. And hanging out in a chemical storage room in your boxers is generally a bad idea.I have a bunch of white phosphorus but it is not stored near me and I don't go handling it in my under pants like someone that was up for 4 days cooking meth.

author: usagi
author_rank: Frequent Contributor
timestamp: July 05, 2018, 07:01:11 am
content: coppercone, stop posting in this thread. you are contributing nothing to this thread and keep sending it off the rails.

author: David Chamberlain
author_rank: Frequent Contributor
timestamp: July 05, 2018, 07:37:35 am
content: Quote from: usagi on July 05, 2018, 07:01:11 amI think this thread would be going fine if every one just stopped feeding the troll. Their is no requirement to respond to everything every one says just move on and ignore it.BTW usagi, I really enjoyed your video and detailed posts last year. Please let us know more about what you changed, or plan on changing, modifications and lessons learnt and so on.

author: usagi
author_rank: Frequent Contributor
timestamp: July 16, 2018, 07:21:58 am
content: i changed everything to wireless this year, which will let me scale up to pretty much unlimited cues. building each receiver takes quite a while though, i'd love to find a decent pcb fab that does pick & place.anyway, the show went well. here's the video.

author: Nusa
author_rank: Super Contributor
timestamp: July 16, 2018, 09:24:04 am
content: Wireless is scary when it's connected to things that go boom. It adds a whole set of new safety considerations in terms of lockouts. You need communications security features on the receiver side in the case of unauthorized transmitters (deliberate or accidental) on your frequencies, or unauthorized users on your transmitters.

author: stj
author_rank: Super Contributor
timestamp: July 16, 2018, 12:27:38 pm
content: it would be better to use the 446MHz LPR band radio modules.you wont have every asshole with a smartphone seeing and trying to mess with your net.

author: usagi
author_rank: Frequent Contributor
timestamp: July 16, 2018, 08:21:33 pm
content: Quote from: stj on July 16, 2018, 12:27:38 pmwhat frequency do you believe this transmitter uses and why do you believe smartphones in the US can mess with it?is there some reason you believe 446mhz is an unlicensed band in the US?

author: stj
author_rank: Super Contributor
timestamp: July 16, 2018, 09:17:15 pm
content: you said "wireless" so i took that to mean wifi modules.search LPR yourself, it's used for stuff like car fobs.

author: usagi
author_rank: Frequent Contributor
timestamp: July 16, 2018, 09:31:47 pm
content: Quote from: stj on July 16, 2018, 09:17:15 pmi'm using encrypted spread spectrum 915mhz, which is a much better solution.315mhz/433mhz car fob frequencies are not available for use in the US for general purpose unlicensed communication. the band use is quite restricted.446mhz which you mentioned earlier is used in Europe for PMR unlicensed. in the US, that is right in the middle of the licensed 70cm band.

author: Stray Electron
author_rank: Super Contributor
timestamp: July 16, 2018, 09:43:44 pm
content: Quote from: CopperCone on July 03, 2018, 01:40:54 amFPAG member and I've been been making safe fireworks for over 50 years. You OTOH don't know WFT you're talking about.I usually ignore threads like this that display obvious signs of major stupidity but I got tired of you ragging on about things that you clearly don't have any knowledge of. In at least half the cases you don't even know the proper names of the items that you're carrying on about.OP, nice work, carry on.

author: Stray Electron
author_rank: Super Contributor
timestamp: July 16, 2018, 09:55:50 pm
content: Quote from: CopperCone on July 04, 2018, 10:23:25 pmBlah, Blah, Blah. The OP talks about a firing box and YOU start carrying on about inadequate wiring and ignitors and now you throw in Nitric Acid, RDX, TNT, HMX and other things that are not and have NEVER been used in fireworks. I'll say again that you have no idea what you're talking about and are just making s**t up! You need to stop before you prove yourself any stupider than you already have!Interestingly there is one high explosive thatat one timewas widely used in fireworks. It's one of the few names that you haven't thrown into your arguments so obviously you don't know what it is.

author: usagi
author_rank: Frequent Contributor
timestamp: July 16, 2018, 10:22:57 pm
content: hi Stray Electron,do you know offhand what typical resistor values are used for igniter safety shunts? commercial igniters are typically twisted shorted for transport, which would be effectively 0 ohms shuntI suspect commercial systems like cobra use some value like 10k.

author: texaspyro
author_rank: Super Contributor
timestamp: July 17, 2018, 04:25:59 am
content: Some day I will write up my high power (fired many P class motors) model rocket launch system...Radios are high power 915 MHz Xbees. Encryption starts with 160 bits of hashed password. Xbee channel and PAN codes provides 2^18 bits of unique radio id info. All messages are signed/verified with 32 bit cryptographically keyed message authentication codes.The firing command is a challenge-response system using a 128 bit key / XTEA encryption and a 64 bit TRUE random number (generated from ADC and IMU noise, etc). When you send the ARM command to the pad, it responds with a double-encrypted version of a 64-bit true random number that the LCO box has to decrypt once and send back with the FIRE command. The pad controller decrypts that number the second time and the results must match the original number. The true random number generator has been verified against numerous random number test suites. The XTEA algorithm has been enhanced with extra rounds and a variable seed value.Oh, and you have one chance and 20 seconds to crack the encryption between the ARM and FIRE commands... the crypto expires after that.

author: usagi
author_rank: Frequent Contributor
timestamp: March 08, 2019, 08:15:16 pm
content: Quote from: David Chamberlain on July 05, 2018, 07:37:35 amFor 2019 i've moved from mechanical relays to Darlington arrays, more integration onto single PCB. Lesson learned, put as much work into the PCB to avoid as much manual wiring as possible.Also going to use pre-fabbed boxes probably from Hammond mfg. Constructing lasercut boxes is a lot of work.

author: Yansi
author_rank: Super Contributor
timestamp: March 09, 2019, 02:38:03 pm
content: Quote from: stj on July 04, 2018, 04:36:34 pmAirbags can't be fired by ESD either. Even 9V battery is struggling to fire one.

author: texaspyro
author_rank: Super Contributor
timestamp: March 09, 2019, 06:25:00 pm
content: Quote from: Yansi on March 09, 2019, 02:38:03 pmElectric matches have a "no fire" and "all fire" spec on current. Any current below "no fire" will not cause them to fire. Currents above "all fire" are "guaranteed" to fire the e-match. Some e-matches have surprisingly low "no fire" specs.

author: DaJMasta
author_rank: Super Contributor
timestamp: March 09, 2019, 08:09:20 pm
content: Quote from: usagi on March 08, 2019, 08:15:16 pmLess setup when you have time constraints and other factors certainly sounds like a good move. Maybe some combination of the two could work for boxes? Something like using a prefab enclosure with a laser cut face for connectors/switches/what have you? Maybe not required if the prefab boxes can meet those requirements, though.

author: Yansi
author_rank: Super Contributor
timestamp: March 09, 2019, 08:23:05 pm
content: Quote from: texaspyro on March 09, 2019, 06:25:00 pmWhy are you quoting me? I am not the one spreading bullshit that ESD can fire an airbag.

author: texaspyro
author_rank: Super Contributor
timestamp: March 09, 2019, 09:30:01 pm
content: Quote from: Yansi on March 09, 2019, 08:23:05 pmI quoted a post about electric match firing current... your part of that post came along for the ride.Oh, and ESD can fire ANY pyrotechnic device, including airbags. It might not fire the pyrogen, but ESD has its ways of causing havoc. Any person involved in pyrotechnics that forgets this fact will eventually be reminded of it in a rather spectacular manner.

author: usagi
author_rank: Frequent Contributor
timestamp: March 10, 2019, 01:18:37 am
content: so my design currently uses port expanders driving darlington arrays.i'm thinking i can get better integration with high power shift registers like tpic6b595...

author: texaspyro
author_rank: Super Contributor
timestamp: March 10, 2019, 02:16:56 am
content: My rocket launch controller uses 2 MOSFETS (rated at 1000 amps) for each channel. There is a high side FET and a low side FET. The ignitor connects between the two. Both FETs have to turn on for current to flow. The gate drive signals to the FETS are generated by transformer / capacitor coupled AC signals that have to be around 30 kHz to get through. No static "stuck at" or transient condition can turn on both FETs and cause a firing condition. The drive waveforms for the high and low FETs are generated by two different mechanisms. Both FETs are continuously monitored for unexpected turn-on. Any faults sound an alarm and shut down the system.

author: Dubbie
author_rank: Unknown
timestamp: March 10, 2019, 02:51:49 am
content: That’s an interesting idea re. The AC gate signal.

author: Yansi
author_rank: Super Contributor
timestamp: March 10, 2019, 08:06:20 pm
content: Quote from: usagi on March 10, 2019, 01:18:37 amVery substandard solution. You will get a pretty firework on a shorted channel too. But not from the business end, but from your transistor array.Any output should be short circuit protected, and preferably shorted at the driver side when inactive.Any fault on any output shall never cause any other output to misfire. Neither may excessive current draw from a channel cause the supply voltage to droop to cause further damage or circuit mis-behavior.Think about it. Solutions may get complicated pretty fast. Hence why the professional firing devices are not simple arduino toys!

author: texaspyro
author_rank: Super Contributor
timestamp: March 11, 2019, 02:12:43 am
content: Quote from: Yansi on March 10, 2019, 08:06:20 pmNumber 1,2,3... rules in my launch controller design is: no single component failure can cause a launch condition. Hence the AC coupled, dual FET switches. All the components in the firing circuits (particularly the continuity / monitoring parts) are through hole... SMT parts are much more likely to fail short-circuit and shorts tend to cause excessive current to flow. Critical resistors are use two in series so a shorted one will still limit currents to a safe level, Although the output FETS can handle 1000 amps, the output current is limited by a 2.4 ohm, 20 watt resistor... that limits the max current to around 20 amps per channel. Timers limit the output pulse to a max of 3 seconds.

author: Yansi
author_rank: Super Contributor
timestamp: March 11, 2019, 01:48:32 pm
content: Quote from: texaspyro on March 11, 2019, 02:12:43 am(text in bold) Not true, at all. Anything to back your statement?Also your solution seems irrational in both design and economical point of view. Strongly, very, very strongly doubt your 1kA rating anyway.Could be probably done much differently but still safely.

author: texaspyro
author_rank: Super Contributor
timestamp: March 12, 2019, 03:55:41 am
content: Quote from: Yansi on March 11, 2019, 01:48:32 pmYes, I have info on failure mechanisms of SMD resistors but am not a liberty to comment further. One thing I can mention is the small spacing between pads that can short during faults that cause solder to melt.The design was based upon over 40 years of experience with pyrotechnic systems and observed, real-world faults that caused unintentional firings. It may appear to be over engineered, but every feature was designed in with special attention to how to prevent those things from happening. Cost was at the very bottom (well, actually totally missing) from the list of requirements. Have you ever designed safety-of-life critical systems?As far as being able to handle 1000 amps... it can for a couple of seconds. Tested with 4S16P A123 LiFePO4 battery. Actually around 2/3 of the power at that level gets absorbed into the wiring and the 2.4 ohm current limiting resistors on the standard firing boards limits the current to around 20A per channel. If you are doing a large cluster you can spread the igniter wiring across multiple channels or short/reduce the current limiting resistor. Applying two much current (or ramping the current too quickly) across an igniter can pop the bridgewire without lighting the pyrogen.

author: floobydust
author_rank: Super Contributor
timestamp: March 12, 2019, 06:17:27 am
content: Quote from: usagi on March 08, 2019, 08:15:16 pmI'm not liking using a multi-channel Darlington array because a shorted channel can affect other channels, in FMEA you consider adjacent pins to short on a single IC as if the die has failed. A ULN200x would not withstand a short-circuit or over-current. I haven't seen the whole circuit though. if there is current-limiting and you only fire one channel at a time.Vishay MEPIC resistor igniterssmaller 0603 sized part is All Fire >0.8A. Another is AEC-Q200 qualified for airbags.They are around 2-10plus cable resistance.

author: usagi
author_rank: Frequent Contributor
timestamp: March 12, 2019, 06:57:41 am
content: igniter profile. 9.32A @ 12V for 200 microseconds to fire.manually tested ~100 igniters, all fire was 0.55A @ 12v. igniters are ~1.17ohm.extremely consistent and reliable, i have been using them for many shows for many years now. igniter wires are 27awg.uC uses completely separate power source from the igniter power source.cues are only toggled for a few milliseconds, as thats all that is needed to fire them. there is a master safe/arm switch, darlingtons choose the cue and an ssr controls igniter power. only one channel is fired at a time.

author: usagi
author_rank: Frequent Contributor
timestamp: April 04, 2019, 09:34:30 pm
content: Quote from: Yansi on March 10, 2019, 08:06:20 pmso here is a video showing the inside of a cobra system. insides are shown around the 2:00 markanother video, around 2:20not that different from my current design.