It looks like we now have another way to annoy ourselves with extremely high voltage.
The bells operate under the same principles as the electrostatic see-saw we covered last month. A voltage is applied to one can while the other can is grounded. An insulated pendulum is placed between each can, and with a little coaxing can be made to oscillate back and forth between the cans. As the pendulum touches the charged can, it is repelled as it gains the charge and moves to the grounded can. There, the charge is released and the cycle continues again. A homemade Cockcroft Walton multiplier is used to generate the +35kV needed to get the pendulum moving.
[Ben Franklin] invented the Franklin Bells while he was investigating electricity in the 1750s. Originally an extension of the kite & key experiment, the bells were historically used to warn of approaching thunderstorms – when the bells rang, the atmosphere was charged and lightning could strike. Even though the voltage between the bells is huge, very little current is drawn – the Oxford Electric Bells have been ringing since 1840 using the same electrostatic battery.
I achieve this effect onstage using a piece of mylar and a Van de Graaf generator. My body acts as the ground and the mylar will fly back and forth between my hand and the generator.
I’ve done this using an old TV as a voltage source. Just covered the screen with aluminum foil.
I did this some time ago myself:
http://www.youtube.com/watch?v=h_cP8HEgIxA
Used one of those Van de Graaff mylar flying toy wands to power it. TV sets also work briefly, as do rectified flybacks or coronatron supplies from photocopiers.
The grounding wire isn’t strictly necessary. The “bells” will ring until the charge on both cans has equalized. Then you can drain charge from the second bell and the ringing will start again even if the original source of high voltage has been removed. Science!
http://www.youtube.com/watch?v=wb7GLs0yM1U
This would also work better if he turned the cans upside-down. Those sharp edges bleed charge.
Soups on!
Was I the only one who read Franklin Balls up there? :-)
@elektrophreak: you saved my day, allready thought i’d be the only one whose brain was down for a second :D
Cockcroft Walden Ladders are the coolest circuit in electronics. The voltages that can be achieved are scary. You need a Ladder to run Soviet Night Vision Goggles and I think that it is wicked cool that you can take 9V and turn it into 3K volts. Plus you can use the Ladders in cattle prods, and stun guns. Some of these Ladders become wicked high and start flaring, nothing like the smell of ozone in the morning!