A Resistor’s Fiery Death Used To Launch Fireworks

Check out this control center which [Awesome0749] built for launching fireworks. From the looks of his stash he’s going to be doing quite a bit of celebrating. The control console is clean and offers some safety features, and he just upgraded to an interesting ignition technique.

He’s using CAT5 cable to connect to the fireworks. At the top of the enclosure you can just make out the edge of the almond-colored wall plates which offer three jacks each. The two keys on the controller must be turned on to power the device. There is also a safety toggle switch in the middle.

The ignition is cause by running 70 VDC through a 1/4 Watt 24 Ohm resistor. As you can see in the demo after the break this results in flames quite quickly. One other thing we saw in the demonstration is that only the LED for the button which is hooked up comes on when the system is armed. We didn’t see a schematic, but he must have wired this so the system checks for continuity to ensure there’s something wired to the business end of the button.

62 thoughts on “A Resistor’s Fiery Death Used To Launch Fireworks

  1. The wiring might be quite simple. Connect the LED with an additional resistthrogh to the ignitor resistor to ground. then Blast the thing and the ground is disconnected and the LED off.

      1. ^ That’s my point. You do something extra — pressing the button disconnects the LED. Thus confirming my assertion that if you didn’t do that, the LED would be in danger. The poster above implied that something much simpler was going on.

    1. I usually facepalm at the pseudo safety comments…

      But here…

      Bench testing igniters just behind a pile of fireworks !? seriously !?

      That’s really beyond idiotic…

  2. Why would you use a resistor for ignition when estes rocket motor igniters are easily had and or an equivalent made? Is there some advantage here or is it just because you can?

    Either way cool. One of these days I’ll get around to building something like this but for me its just as much fun running up and down the beach with a blowtorch

    1. Estes ignitors retail for a dollar apiece in a six-pack – if they have a bulk rate I can’t find it because their site is broken. 1/4W resistors can be had for pennies apiece, and can easily be bought in the hundreds.

  3. I did something similar a few years back, but instead of resistors, I got a roll or Nichrome wire! It’s what model rockets typically use to light their engines. This year I made a handheld “lighter” with two AA batteries, a push-button switch and an inch of Nichrome wire. Works great and is reusable!
    Btw, Great hack!

      1. I saw before someone had set up reusable clips with Nichrome wire in them — basically you just clipped them on to the end of a fuse and hit a button — they were a little harder to make, but you could reuse them a couple hundred times before you had to make new ones.

  4. Looks similar to how proper pyro desks work.
    also, pyro igniters work on basically the same principle, a fine piece of wire dipped in a protective coating, small voltage to check for continuity (nothing worse than a fx that doesnt go off) and the full fat power to make it pop.

    never wire in series though, they are unlikely to go off at exactly the sme time so you end up with a break in your chain and only one fx going off

    1. On professional ignitors that isn’t a protective coating, it’s an igntion compound. Usually based on sulfurless blackpowders and/or nitrocellulose.

      I know resistors are cheap but are they really cheaper than NiChrome wire? Especially if you can salvage it from something.

  5. Seriously I just designed myself a firework console
    thats weak, first 70V…. comeon on the field tell me where you get it need a generator?
    a resistor…. slow…
    you have to hold down the button????
    not enough rj-45 connector (wich I also used but I got 25 connectors) they have their down side too but if you take care of them thats good.
    you have to be close to your firework lunch site thats a terrible idea. go wireless….
    ill be happy to help if you wish to do a rev. 2

    1. I saw a great system that used the circuits out of remote garage door openers to trigger the firing.

      Ive also seen a pro system that uses RJ45 for the connectors. all the fireworks have rj45 on the end and you just patch them into the button you want :)
      Or you plug them into a rail which you can mount them on/hang them off and then a cat5 into the rail and your good to go

    2. Looks like they plan to be 100′ from the launch area, lot more than most who manually light them off would be. Holding down the button could be part of the fun perhaps

      1. Holding the button is nice actually, you get to feel like you’re actually manually lighting each firework. The closest thing I would compare it to holding A harder when trying to catch a Pokemon.

  6. I used to use a strike-anywhere match masking taped to a 1N914. Back in the day you could get 50 for a buck and change at Rat Shack. Just forward bias it with a 9V battery to light.

  7. wouldnt an electric match used for model rockets work?

    unless they contain some substance that is controlled and in the quantity needed it would raise suspicion for some illegal use.

  8. I have done some experimenting with this and run in to several problems:

    1. modern resistors (metal film, carbon film) are unpredictable and/or slow. If you use a current high enough to make the resistor hot in a short enough time the resistor is likely to break without heating up. And obviously if you use a lower current ignition is going to be slow and unpredictable in timing.

    2. These things will use a lot of energy compared to other means, but a lot less current than nichrome or professional ignitiers. It is not trivial to build a small battery powered system with enough power to quickly and reliably ignite a nicrome or professional igniter.

    One thing i tried was using carbon mass resistors, these burn out a lot more reliably at very high currents, but i still need to put over 30 joules through them to ignite them reliably and fast. My test setup used a 150 ohm carbon mass resistor, a 300-350V camera flash and a very high current IGBT to push something like 600W through the resistor for a very short time. This works very nicely but may still need some work since it does not work 100% in really cold weather, i do suspect i’m just using too small capacitors though.

    The main problem with my solution is of course that carbon mass resistors are no longer produced.

  9. I used to use small diodes wrapperd around match heads dipped in parafin you could check polarity
    one way and reverse and ramp up the voltage and it is almost instant

  10. Oh, i just read through the comments and realized people are trying to ignite the fuse.

    Just to be clear, i intend to ignite mortar type fireworks directly so what i do is remove the fuse and replace it with an igniter, and i also want as close to instant triggering as possible so a slowly heating resistor won’t do.

  11. i’ve had quite solid luck using christmas tree lights with the bulb broken off. score the tip of the bulb, crack it off. continuity checks for unbroken filament and power produces instant ignition. for fuse lighting, you can build the igniter around the fuse with a *little* bit of black powder or flash cotton to ensure the fuse catches and tape it to the fuse for transit. onsite just plug into a socket from the donor string of lights wired to the control box.

    if you’re getting fancy, protecting the filament with nitro lacquer works beautifully.

  12. …since you can be electrocuted by 40VDC with damp skin. Anything over that voltage must be protected better than just running cat5 through the grass.

    You could probably eliminate this risk by tweak this idea to run on 24V, or even 12V by using lower resistance lower power handling resistors.

    Just sayin’

    1. My box is powered by +/-35V, not enough to do any damage except a little finger numbing shock here and there. And the chassis is grounded in case of a short from something inside the box to the box. And remember, in order to get the resistor to heat up and not the wire, the resistor has to have a higher resistance than the wire. My 24 ohm resistors only work with my higher quality cable from monoprice.com. My crappy cables have a higher resistance, so they need a 51 ohm resistor.

  13. This sort setup is similar to an exploding bridgewire ignitor. One better method for setting this off may be to use a high-tension capacitor discharge through the bridgewire. Discharge enough energy through bridgewire in a short enough period of time and it’ll flash to plasma. That should set off a black powder lifting charge. You easily can source the bridgewire by using a single strand from stranded copper wire. The discharge can be controlled either with a high current IGBT or a SCR.

  14. I didn’t have time to read the other comment’s; no disrespect intended to the masses. Why you are using resistors is beyond me. I think you should go back to the drawing board; for safety and education. The fact that you have chosen such a poor solution to ordering match tips is beyond me. Buying the ready to dip set-ups can get expensive, however I assume you can solder so this should not be an issue.

    Last words of advice: thing you don’t want:
    1 having an e-match pop, causing a tiny report and ejection
    2 the need to use the high level of voltage you are using
    3 have bugs is your ignition logic or an improperly grounded line of fire

    I am not trying to insult you the design you have was one of my first thoughts before I began to educate myself as you need to do. Pyrotechnics is a passion of mine and safety always comes first, before during and after a project event or design; safety is always #1 and your neighbors, crowd, roommates/family are your first and primary concern. Embrace this hobby but treat it with respect and do it right.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.