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Oxford Electric Bell (wikipedia.org)
109 points by okket on Oct 6, 2018 | hide | past | favorite | 12 comments

Previous discussions:

2014: https://news.ycombinator.com/item?id=7833010 (60 comments)

2013: https://news.ycombinator.com/item?id=5995422 (13 comments)

It's fun to make one of these: use two metal coffee cans, suspend a washer between them using string tied on a plastic comb or something. There should be only a small gap between the washer and each can. Charge one of the cans- rub styrofoam on fabric then touch it to one of the cans. The washer will swing back and forth, transferring the charge from the can you touched to the other one. It makes quite a racket.

You can make a chain of these.

I used to work at the Clarendon Lab and made this video about the bell while I did:


How many joules or watt hours has these used?

Some quick, back-of-the-envelope-math, suggests the total energy used amounts to about 1'389 mAh (roughly 5 Coulombs, based on an article saying it transfers about 1 nanoampere of current per ring and rung about 10 billion times since it was completed).

Watthours and Joules is difficult to know without measuring the voltage on the device, which would also have to involve the change in voltage over time to get a more accurate number. I'm probably wide off once you account for the reduced power over time.

You'd think a battery like that lasting decades could be quite handy for internet of things devices. You could maybe use a capacitor to accumulate power as the output seems to be in nano amps and low current processors seem to need about 1 uA upwards. Not sure if anyone is working on that stuff?

> You'd think a battery like that lasting decades could be quite handy for internet of things devices

We probably have to invent a standard that lasts one decade first.

The humble AA/R6 battery has been around since before WW1.

Obviously, the capacity has improved vastly, but the size, terminals and voltage has been with us since your great grandfather wore diapers.

I think GP was referring to a software or service standard for the IoT device to interact with rather than a hardware standard.

Battery technology has improved dramatically since 1840, many quartz watches have battery life measured in years.

What you're proposing exists, it's just expensive because demand is low.

Electrically readable water meters have a lithium battery that lasts for decades.

I firmly believe there’s an ocean of undisovered applications for electrostatics.

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