Electronics > Projects, Designs, and Technical Stuff
My arduino powered firework sequencer. 2018 version!
floobydust:
--- Quote from: usagi on March 08, 2019, 08:15:16 pm ---For 2019 i've moved from mechanical relays to Darlington arrays, more integration onto single PCB....
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I'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 igniters smaller 0603 sized part is All Fire >0.8A. Another is AEC-Q200 qualified for airbags.
They are around 2-10 \$\Omega\$ plus cable resistance.
usagi:
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.
usagi:
--- Quote from: Yansi on March 10, 2019, 08:06:20 pm ---
--- Quote from: usagi on March 10, 2019, 01:18:37 am ---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...
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Very 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!
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so here is a video showing the inside of a cobra system. insides are shown around the 2:00 mark
another video, around 2:20
not that different from my current design.
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