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Simple, low power, electromagnetic pendulum drive system
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- Опубликовано: 17 авг 2024
- This is a little gadget that may be used for simple animations.
Note - I've just posted a new video using a practical electronic drive, that does not need the mechanics switch: • Electromagnetic Pendul...
The exact mechanical form does not matter as long as it has a free-swinging pendulum of some sort with a curved non-ferrous lower section running through a small solenoid (eg. stripped out relay) coil, and a slim magnet with north & south at the ends, fitted to the centre of that curved section.
Coil activation is by a simple springy contact switch that makes momentarily as the pendulum gets to the centre of the its swing and breaks again around the point the magnet leaves the coil, either way.
As I've built it, it runs well on a single 1.5V cell.
Brillié French clocks worked in this way with a single C cell (or was it a D one?) back in 1900 ~ 1920. Beautiful pieces of incredible simplicity and amazingly efficient. The time the coil is energized can be tuned to be so short that on a modern alkaline battery it can easily work for 2 or 3 years.
Oh, I'd like to add that the Brillié clocks had an horizontal U shape iron mass in the pendulum, one of the U legs inside the coil, this to make a magnetic flow as closed as possible leading to a really weird looking pendulum ;)
What I don't remember is if that U was magnetized or not, because you can achieve a somewhat similar effect with just the non magnetic iron being attracted.
This is excellent!
Thanks!
Like a little section of a particle accelerator.
Hello. I had a similar toy. there was one transistor inside. and the coil had two windings. powered by 9 volt battery. a magnet was swinging above the coil.
nice work! really informative.
Thank you!
Excellent machine, would make a great clock with nixie tube counter .Engineering + "ART" . I really like this piece.
Glad you like it!
Nothing new here. The same mechanism was used in advertising display as far back as at least the mid 1950s. We had such signs in my father's television shop in the 1950s.
Exactly! I mention in the video that it's built from my memory of an ex shop display gadget that my older brother had, back in the 60s.
Ive always intended to modify a pendulum driven clock to use a coil to provide the impulse, yet let the pendulum determine the timing of the impulse by using an optical detector.
I don't know is a single opto switch would work directly, and give the required past-centre timing - but a centre opto switch trigger and a monostable may work, or three opto switches at centre and either side, so the swing direction can be determined with some simple logic?
Centre switch to energise the coil after one outer has been seen, then the other outer to turn power off again as the magnet clears the coil?
With a real, weighted pendulum, it's starting to sound a bit like an updated version of the old electromechanical "Master clock" system!
how would you slow the movement down? that's swinging way to fast -
A longer pendulum - the rate is set primarily by the distance from the pivot to its centre of gravity; it should have a reasonable end mass compared to the support parts so the C of G is near the lower end. Roughly 99cm gives around a two second cycle (one second each way), or 25cm around one second for a full cycle. Adjusting the length from the pivot can tune the exact rate.
Or operate it in a weaker gravitational field.
could maybe use a reed switch and magnet for the top contact and it would be silent
I thought of that, but I was not sure how to guarantee it stayed closed long enough each way, without closing before centre and slowing the pendulum. That's for a later version anyway, this is minimalised to show the principles involved.