I have a show which uses a Tesla Coil based electric chair. Toward the end of the show, we simulate a system failure with electronic firecrackers and smoke. We have five 25 watt light bulbs on each side of the chair. I would like them to flicker randomly simulating this failure. What is a simple way to get this effect?

 

Do you want them to flicker independently, or all together? Are these 120v incandescent bulbs? It's harder to flicker them quickly because the filament takes some time to heat up or cool off.

 

They can all flicker together. They are 120V. I had not thought of the "recycle Time. I am thinking that it should not be rhythmic, but perhaps I am over thinking it. When the fire crackers go off, I am momentarily "stunned". Then I panic and start yelling to "Turn Off The Power". The power is actually turned off by a member of the audience who has been operating the big, old fashioned switch throughout the show. The entire "failure" episode is probably only 10 seconds. Under the worst circumstance, it would not be more than 15 seconds.

 

Between the Tesla coil and being wired with 120 VAC, I hope that a real person is nowhere near the chair!

I've made similar props, and for the"firecracker" simulation, I'd use 12v LED bulbs, and drive them through a ring oscillator or pseudo-random number generator. The output of the logic (parallel outputs) would go to a driver circuit for the lamps.

 

Another approach would be to use a microprocessor to deliver whatever preprogrammed effect is desired, and then use that to control the driver circuits. I did something similar by hacking one of those cheap, flickering LED candles to drive a MOSFET so that a much larger lighting load could show the same flicker as the little LED. Of course the challenge is to find a suitable effect. My LED candle was easy to find. Not sure where you'd find a "shorting explosion" effect. But if you had your own microprocessor driving the project, you could try different programs until you found the one you like.

 

Another approach would be to use a microprocessor to deliver whatever preprogrammed effect is desired, and then use that to control the driver circuits. I did something similar by hacking one of those cheap, flickering LED candles to drive a MOSFET so that a much larger lighting load could show the same flicker as the little LED. Of course the challenge is to find a suitable effect. My LED candle was easy to find. Not sure where you'd find a "shorting explosion" effect. But if you had your own microprocessor driving the project, you could try different programs until you found the one you like.

Between the Tesla coil and being wired with 120 VAC, I hope that a real person is nowhere near the chair!

I've made similar props, and for the"firecracker" simulation, I'd use 12v LED bulbs, and drive them through a ring oscillator or pseudo-random number generator. The output of the logic (parallel outputs) would go to a driver circuit for the lamps.

Thanks guys. You are both a bit over my head, but I have a helper who will understand this. We will be back in a week.

 

The concept is a signal, something that conveys the information of what your desired effect looks like, controlling the power needed to light those lights. They're two separate challenges and work on one can proceed without the other. Sort of.

It's a bit like in audio where you have a pre-amp that does all the manipulation of the input signals, and then a power amp that actually drives your speakers.

 

The concept is a signal, something that conveys the information of what your desired effect looks like, controlling the power needed to light those lights. They're two separate challenges and work on one can proceed without the other. Sort of.

It's a bit like in audio where you have a pre-amp that does all the manipulation of the input signals, and then a power amp that actually drives your speakers.

Great analogy. My computer dude can create the signal, but we did not know how to do the power amp.

 

to get an explosive overload type of visual you could make a hole in the bulb and let air have access. The best effect might be had by using small 12V automotive bulbs and 'triggering' the bulb to blast visually and even throw some spark and smoke by hitting them with 120 VAC. This would be a one time effect for the poor little automotive bulb of course, but should give a good visual effect in a darkened room.

 

That's why I asked about the bulbs. The LED suggestion is a good one, but it sounds like you are locked into the 25W bulbs?

Dimming of incandescent bulbs like yours is done with a TRIAC dimmer circuit. Instead of a knob to turn, you'll use the small DC signal from a computer to control the dimming. This signal will pass thru an optocoupler to safely isolate it from the AC circuit powering the lights. I haven't built one personally but maybe someone here has a design they like. Their are tons on the internet but you're better off with one that has been tested and verified. Lots of crap out there.

 

We presently have five different levels of voltage applied to Madam Electra. Actually, it is just sound effects. We then put a stack of five old fashioned "Edison" style 25 watt bulbs on each side of the chair to indicate the "voltage" level. That is done. The premise is that this is all 1920s stuff. Then we got the idea of making them flicker. We have made a single bulb flicker by putting it in series with a Florescent starter. That was fine with one bulb, but 10 bulbs is a different game. Each of the five pairs of bulbs has their own power wire, but they all share a single ground. My guess is that we put your gadget in the ground wire. When the timer kicks the fire crackers, it initiates the flicker routine.
If I had discovered you guy sooner, I might have done it differently, but we have what we have. It has evolved for several years. With this last change, it may be fully evolved. ay times I toy with the thoughts of increasing the power, but Madam Electra does not like that idea.

 

Each of the five pairs of bulbs has their own power wire, but they all share a single ground. My guess is that we put your gadget in the ground wire.

Polarity doesn't matter in an AC circuit. The dimmer can go on the power wire or the neutral.

 

A "tea light. flickering candle" flickers 120V AC bulb when loosley coupled to a Dusk-to- Dawn Light Control. Used this several years ago for another post.
New unit just now tested fron ACE Hdw. Westek, SLC4CG, 150W max. incandescent.

 

A "tea light. flickering candle" flickers 120V AC bulb when loosley coupled to a Dusk-to- Dawn Light Control. Used this several years ago for another post.
New unit just now tested fron ACE Hdw. Westek, SLC4CG, 150W max. incandescent.

Would I need one for each bulb (ie 10 of them)?

 

Would I need one for each bulb (ie 10 of them)?

I just redid my math. I would need one from each side. That would be 125 watts per unit.

 

If blinking needs to be same on both sides, tea light can be made to drive several control LED's.
Another exp. for Madam uses PWM from simple 555 ckt. Result is blinking with dimming. Some wierd effects.
Dimming level can also be set with individual resistors and rotary switch rather than a pot.
What part of world are you in?