Last year my home state, Michigan, legalized aerial fireworks. I put on a small show and really enjoyed it so I wanted to step it up this year. I made a 4 channel firework launcher capable of igniting 16* individual firework fuses.
Finding anything with a fuse in Colorado is actually pretty hard. I had to have some visco fuse mailed and it took a while. Naturally, that didn’t stop me from making stuff.
It took forever to whittle those clothespins and they really came out nice. Unfortunately once I received the visco fuse I realized the 40awg nichrome just didn’t have enough oomph to burn through the outer layer. I think this design could still work well with some lower gauge nichrome.
This is the main box. It has a 5v 16mhz ProMini, 12/5v 2a power supply and 2 10F 2.5v super capacitors. These 4 RCA inputs allow an external button to fire each relay individually. When nothing is plugged in they are all routed to the red button under the toggle switch
When the input is fired the arduino closes the associated relay in this smaller box giving 4 of the DC barrel jacks 5V.
This setup gave me a little more grief than I’d have liked. The arduino could fire 3 of the relays at once but not 4. To fix this, I had to let the arduino sink the current instead of sourcing it which led me to an inductive feedback problem but it was easily solved by adding a diode across the load.
The most reliable way I’ve found to ignite visco fuse with 40awg nichrome is to use a needle and thread the wire through the fuse. Throw a little electrical wire so that it doesn’t pull out. I give the wire enough current long enough for it to break.
Everything fit in fairly well, there is a cubby on the box lid to hold the spool of nichrome and the relay box fits fairly snugly.
The arduino is running a simple program that can be found here. You can configure a delay before firing each individual relay.
I was too scared to risk burning the state down or getting a fine, so here is a fairly underwhelming demonstration: