Is it possible to build a low-voltage Thompson jumping ring apparatus?

[CrayV]

TL;DR Summary

Will I be able to create a jumping ring apparatus with just 12V?

Hi all, I'm attempting to build a jumping ring apparatus (a core of iron with the bottom wrapped with wiring like an electromagnet, so that when a metal ring is placed on top of the coil and a current is run through the coil, the ring jumps up into the air). Looking on the internet, I'm seeing a lot of high voltage versions of the apparatus, though I am limited to 12V. Does anyone know if it's possible to build this with a limit of 12V?

Any and all help is greatly appreciated.

The apparatus I'm describing can be seen here:

 

[Baluncore]

Welcome to PF.

The jump is caused by the magnetic field produced by the coil, reacting against the current induced to flow in the ring. The same ring can be used with the lower voltage.

The strength of the magnetic field is proportional to the number of turns multiplied by the current. For a lower voltage, you will need a higher current to deliver the same power. The number of turns will need to be reduced in the same ratio as the voltage is reduced. The same weight of copper will be needed, so the coil will need to be wound with thicker wire or flat strap.

 

[Borek]

number of turns multiplied by the current

Which technically is just a total current flowing through a cross section. Obvious, but always made it easier for me to understand what is going on.

 

[sophiecentaur]

The same weight of copper will be needed, so the coil will need to be wound with thicker wire or flat strap.

Doing it a low voltage would require an equally beefy step down transformer. I think that's probably why the demos I've seen use a mains voltage inductor. But when I was at school, the Physics master used to heat a beaker of water with two nails connected directly to the mains. We were hard in those days.

 

[Baluncore]

Doing it a low voltage would require an equally beefy step down transformer.

From mains power, yes, but not directly from a 12 volt car battery.

We were hard in those days.

"Too tough to care".

 

[sophiecentaur]

"Too tough to care".

Too tough for the teachers to care. We knew nothing!

From mains power, yes, but not directly from a 12 volt car battery.

But that would require an inverter(?). Even more trouble and expense, I think.

 

[Baluncore]

But that would require an inverter(?). Even more trouble and expense, I think.

The DC turn on transient is sufficient for the initial jump.
It is levitation that requires an AC waveform.

 

[Swamp Thing]

If we are looking for the jump rather than steady floating, maybe a step-down circuit using capacitors would work? Like connect a few capacitors in series to a 1.5 volt (or even 9V) cell, then put them in parallel and connect to a single-turn loop made from a copper strip.

 

[Baluncore]

Like connect a few capacitors in series to a 1.5 volt (or even 9V) cell, then put them in parallel and connect to a single-turn loop made from copper bus-bar stock.

That appears to be a Marx generator, operating backwards.
https://en.wikipedia.org/wiki/Marx_generator
Implementation will require the control of multiple high-current, low-voltage switches.

The electromagnetic core needs to be designed for some optimum frequency. The connection of a charged capacitor to the inductive coil will result in a damped resonance, at a predictable frequency. Select the capacitance to match that resonant frequency, to the core.

I expect the design of a "jumping ring" system, will actually come down to the current that the switch must conduct, and so to the cost of that switch.

 

[sophiecentaur]

The DC turn on transient is sufficient for the initial jump.
It is levitation that requires an AC waveform.

You are right - but the OP posted a video with levitation in the demo. So this AC/DC distinction must be relevant for him.

 

[sophiecentaur]

If we are looking for the jump rather than steady floating, maybe a step-down circuit using capacitors would work? Like connect a few capacitors in series to a 1.5 volt (or even 9V) cell, then put them in parallel and connect to a single-turn loop made from a copper strip.

With the sort of inductance that a home wound inductor would involve, I'm thinking that you'd be needing some pretty damn fat capacitors. Low voltage circuits need low impedance loads to get high current through them. It may be worth an experiment with a big (chuck-out) transformer core and a kilo or so of wire - not cheap an d possibly not re-usable unless the OP is already a DIYer.

But, now I've looked around, I haven't found an example of this demo that doesn't use AC. However, rather than using actual levitation, it would surely be possible to deflect a ring horizontally (suspended on a string), using switched on DC (and switched off too). Not as impressive as making holes in the lab ceiling but it would make the point.