- This is a "perpetual motion" device.
That's the first time I've ever used a green screen
in one of my videos.
But it's important to put perpetual motion
in inverted commas because perpetual motion doesn't exist.
Actually, the designer of this device
calls it a perpetual motion simulator.
I quite like that.
Actually, I quite like
perpetual motion simulators in general
because we know that perpetual motion isn't possible,
so it's fun to try and figure out like where's the trick?
And in this particular case,
the trick is some really lovely engineering.
To be clear, I don't like perpetual motion simulators
that are designed to scam people.
The list of those is endless,
but the creator of this device
is very clear that it needs batteries.
In fact, I did some bookkeeping
after buying all the stuff for this video,
and I chuckled at these two entries,
perpetual motion machine followed immediately
by batteries for perpetual motion machine.
To figure out how this works, we really need to look inside,
and thankfully through the magic of buying two of them,
I already have a taken apart one right here.
And that's the second time I've ever used green screen
in one of my videos.
The idea was to remove the wooden base
and replace it with a transparent one, because, you know,
I like to make transparent versions of things.
The problem was when we put all the gubbins back in,
we couldn't get it working again.
So while this is good for showing you what's going on,
it's a bit unsatisfying because it doesn't actually work.
And then I thought, "Wait a second,
why don't I try and contact the person who made this thing?"
William Le was very helpful giving advice
on how to get this thing working, but we never could.
So eventually I asked if he would make one for me.
And so here is my third perpetual motion simulator.
Isn't it beautiful?
I'm hugely grateful to William for making this for me.
He took the time to figure out
how to work with unfamiliar materials,
and the result is fantastic.
By the way, William is the creator of this design.
There've been hundreds of knockoffs since,
but if you're planning to get one of these,
I really hope that you'll go to the original creator.
The link to William's Etsy page is in the description.
So let's figure out how this thing works.
Well, even without looking inside,
we can make some educated guesses.
Without the device turned on,
you can see the losses due to friction.
Gravitational potential energy is turned into kinetic energy
and that kinetic energy
is turned back into gravitational potential energy.
But look how much less gravitational potential energy
there is after that process.
So when the device is turned on,
the ball must be given some additional kinetic energy
at some point.
And the only thing I can think of is electromagnets.
And in this transparent version, that's what you see here.
But that's not enough on its own.
If you simply turn on the electromagnet,
well, the steel ball will accelerate towards it,
but once it reaches the electromagnet,
it'll be harder to leave.
This is what happens when I put a permanent magnet
in place of the electromagnet.
So the electromagnet needs to be on during the approach,
and then off once the ball reaches the magnet.
That's where this component comes in.
This is an inductive proximity sensor.
Actually, no. This is an inductive proximity sensor.
This is one of these that's been deconstructed by William
so that it'll fit inside his sneaky device.
The way it works is when you supply power on these two wires
an oscillating current passes through the coil inside
which induces an oscillating magnetic field.
You might know that a changing magnetic field
induces a current in nearby metals.
Well, an oscillating magnetic field
is changing all the time.
So when the steel ball approaches,
an oscillating current is induced inside it.
Now that oscillating electric current inside the ball
has an oscillating magnetic field of its own.
And the way the physics works out,
that induced magnetic field
actually opposes the magnetic field of the coil.
So as the ball approaches,
the total magnetic field goes down.
That's detected by the sensor and this little LED light up.
But for the purposes of this circuit,
it also sends a signal voltage down this third wire.
So now we can have the electromagnet turn on
when the ball gets to a certain position.
We can then decide
like how long do we want the magnet to be turned on for?
I've attached a voltmeter across the electromagnet
so you can see a voltage is supplied
to the electromagnet for about 10 milliseconds.
Final couple of things I wanna look at.
What are these things? Well, these are capacitors.
You really need to give that electromagnet some juice.
So instead of powering it directly from the battery,
you charge up these capacitors and then power it from them.
I'm not sure how long it takes
to charge up these capacitors,
but if you send two balls down at the same time,
the second ball doesn't make it.
But if you leave a little gap between the two,
then they both come back to the top.
And actually looking at the voltage graph from earlier,
the capacitors don't discharge very much at all.
So you can imagine it wouldn't take much time
to get them back where you want them
before the next ball arrives.
These two blue components are important.
They allow you to adjust
a couple of the parameters of the device.
You tweak the top one
if you want to adjust the strength of the electromagnet,
and you tweak the bottom one
if you want to adjust how long the electromagnet is on for.
And these are important
because each one of these devices is handmade.
There's gonna be a slight variation
in the distance between the rails and the sensor,
the length of the track and so on.
So you need to be able to fine tune these things
after it's all put together.
I mean, you don't have to.
William does it before he sends it.
The final thing is the power button.
You know, you really don't want
your perpetual motion machine to have a power button.
It kind of spoils the illusion a little bit.
So here under the acrylic, you can see a capacitive sensor.
When you touch it,
you're adding the capacitance of your body
to that little bit of acrylic there.
That sensor can detect the change in capacitance,
and the circuitry interprets that as a button press.
And so in the wooden version,
it's as if there is no power button.
On the subject of perpetual motion, actually,
occasionally I'll make a video that demonstrates
some physical principle typically involving magnets,
and there'll be a discussion in the comments of like,
"Would it be possible to slightly adjust the setup
so that the thing keeps spinning forever
or the thing keeps bouncing up and down forever?"
Things like that.
A good example is my video about the spinning ballerina toy.
What if you had two magnets or a ring of magnets
so that the ballerina just constantly moved round
in a circle?
But actually you'll notice in that video,
I'm always moving my hand.
The magnet is always getting closer and closer
to the ballerina,
and the ballerina is getting further and further away.
And of course, the ballerina
is pushing back against my hand, so I'm doing work.
My hand is moving some distance
in the direction of an applied force,
so there's no free energy to be had here.
And of course, there's no free energy here either,
unless you don't pay for your electricity.
♫ perpetually smooth jazz ♫
And thankfully through the magic of buying two of them...
And thankfully through the magic of buying two of them,
I already have a taken apart one right here.
I picked up the wrong one.
I used to get these phone calls where they'd be like,
"Hello, am I speaking to Steven Mould
of such and such address?"
"Yes, that's me, that's my address."
And they say, "I'm calling from insurance department."
Okay, they know my details.
They must be calling from the insurance department
of my insurers.
But then you carry on the conversation,
it turns out they're just trying to sell you life insurance
or something like that.
It's really interesting
to know how these annoying practices came about.
It's also interesting to know
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You can contact these data brokers and tell them to stop,
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I hope you enjoyed this video.
If you did, don't forget to hit subscribe,
and the algorithm thinks you'll enjoy this video next.
(lively music)