Hello, I have recently assigned a project, for theatre, to construct a small flash device for special effects in a musical. The device is just a plug, a push-button in a series, and a fuse on the other end. The fuse, old style one, has the glass window cut out and flash powder poured in with duct tape sealing it in. When the circuit is complete, the sudden jump in amperage, due to the low resistence and high voltage, will quickly engage the fuse to overheat and melt. The heat will be enough to trigger the flash powder's vaporization point and ignite it. I want to add a safety device to the circuit by supplying a neon light, in parallel, to the fuse so that if the unit is plugged in and the circuit is somehow complete, the fuse will light up. This will notify anyone who is going to install one of the modified fuses to not install it because the circuit is live. My question is that if a neon fuse is placed in parallel with the fuse, will the standard fare of triggering the fuse be defeated since the load across it will absorb the current? The fuse will be rated about 3-5 amps. Thank you.
That's a pretty neat way to set off some fireworks for July 4th! A neon bulb in series with a resistor and the combination in parallel with the fuse will not affect the operation of the circuit. The fuse would be basically a short circuit, while the bulb and resistor would be 100K ohms or so, depending on the bulb and resistor.
I have done something pretty much exactly like this, except i used 2.4V light bulbs from a christmas light instead of a fuse. The reason i did that is that i want to be able to use small battery powered trigger systems. These work great, if a larger blast is needed, you just fill a bulb with black powder and put it into the larger load. Oh, and this stuff is VERY dangerous if you don't know what you're doing, read my signature before attempting anything
Thank you for the answers. My director actually had the idea but assigned me to it since he knows I am into that "electronic magic". To go into a little deeper, you have to poke a few holes in the duct tape to give it a little leeway. The less holes - the bigger the sound; the more holes - the more smoke. And yes, the auditorium's caretaker has given us permission to construct and use the flash device on stage.
Don't know about the caretaker, but here in England you would need to inform the local fire station that you are using pyrotechnics on stage, in some counties you would also need a licence from the local council. You then need a qualified fire office on standby during the time the devices are armed. I'd be very careful with homemade pryrotechnics, I've worked with professionals in the industry and they still get stuff wrong, or things don't happen that are expected. If I were you I'd hire a proper firing system from a local theatre hire shop...
That would depend on the size of the pyrotechnics thou, you don't need a license for using stuff like party poppers, blank firing guns and such, even if you need a license for owning the guns in some countries.
No reason why you can't do that with a bit of fuse wire and a car battery, deliberately blowing mains fuses can sometimes blow the higher-rated fuse or trip breakers on the supply, apart from the voltage risk. Or use a spare PC PSU with a 15A-20A current-limit resistor in series with the fusewire.
I was using 4 AA batteries and about 10-20 meters of thin Cat5 wire, so i wouldn't get the currents to burn out any standard fuses, the low voltage light bulbs are perfect for this, i haven't had a single misfire of over 50 with 3 kinds of pyrotechnical powder. Blackpowder, silver/flaspowder and white rocketpowder. Fuses are allso more expensive than buying a cheap christmas light and stripping them of the bulbs, i got about 15 bulbs to the dollar, and a neat 24V 60VA transformer.
The caretaker works for the city and often collaborates with the various departments so I am sure he and/or the director will take care of the paperwork and precautions. The battery idea and christmas lights sound pretty good; I will pass that on to the director when I see him. Thank you.
The high voltage will increase the odds of an arc forming, which in turn increases the odds of the fireworks working as expected. I remember that when a friend did something like this, he actually used a heater as a current limiting resistor. It was connected in series with the hot wire, and some AWG30 wire was used to light the fireworks. When a power relay on the relay card turns on, the circuit was completed. The AWG30 wire would get hot and melt, arcing in the process. The arc would set off the fireworks. A christmas light was used as a power on indicator.
