Having recently taking a look at a fairly complex Um pendulum circuit with two transistors that self-stars I thought it would be interesting looking at the simplest generic clock pendulum socket. It's not the simplest because the symbol is just literally as a coil and a transistor, but this one Uh is designed for super low current operation and as such, the components are just optimized to drive this coil and keep a pendulum. Swinging with very low drain on a 1.5 volt cell that is also used to power the clock section. So take a look at the circuitry.

We have a coil and the notable difference between that and the previous unit I showed is that this coil is Center tapped. It's basically two coils, one for feedback and one for actually providing the magnetic kick. There is an electrolytic capacitor which is a value of a 47 microfart. There is a decoupling capacitor 100 nanofarad.

There is the transistor and then the very high value one Mega ohm resistor which is used to provide a slight bias to that transistor. The back of the circuit board is not terribly exciting. Um, other than the fact I've drawn the components on it, but there it is for your reference. let's take a look at the schematic and at this point in time, I'll just make sure that I get relatively close to this without going into Super potato Vision because uh, the camera is mounted much further away than it normally is when I'm making these videos.

Here is the double A battery that is powering both the clock mechanism and also this pendulum section. The coil, excuse me. The coil has two windings. It's got a center tap winding effectively with 900 Ohms on either side.

That makes it quite difficult to wind these coils because it's very, very fine wire, but it's not that hard if you get used to. Basically, you've got a big wheel of the wire and you've got a cordless drill and you make a little adapter for your air cord coil because these ones, uh, don't have a steel core through the coil, it's just air cord. But if you can find a suitable bobbin. I've used sewing machine bobbins.

the plastic ones the the really small ones are designed to fit under the foot plate of the sewing machine. and uh, if you do that, the sewing machine itself usually has a winding mechanism on it, so you can actually use that to wind your coil. I've done that in the past with success, but the coil is in two sections. two 900 ohm sections Center tapped to the the positive.

Supply The transistor is used to switch this section to give it the magnetic pulse, but also to couple back to the other one to amplify that. So what happens is that. um, there is a very slight bias via this coil in this one. Meg Ohm resistor just to provide a very, very slight bias onto the base of this transistor.

That means the transistor is a little bit more sensitive because it's almost turned on already. Um, there's a hundred nanofarad capacitor here I Think that's purely for damping to basically help absorb possibly the back. EMF Spike when this turns off, but also potentially to dampen it so it doesn't start or sleep at a very high frequency. Because if this coil because because it's ear curd, it could also eat an extremely high frequency.

And that's probably to damp that down. Ensure that it only does single pulses when the magnet passes. When the magnet does pass, it induces current in this coil and that is coupled capacitively to the base of the transistor. The capacitor has to be there for a couple of reasons: It rations the amount of current that can actually flow um in each cycle.

But also, if that capacitor wasn't there, the current would simply flow through this coil and uh, straight into the base of the transistor and it'll just turn on all the time. So it's needed for separation. When the magnetic pendulum does swing by, it induces a slight current in here that starts to turn the transistor on. When the transistor starts turning on, this coil is energized and there's a feedback magnetic feedback in the sense that as this one is pulled down to the negative, this end here goes positive and it amplifies that so that initial trigger pulse from the magnet is then boosted up and uh, the feedback ensures that this gets a nice solid pulse.

That pulse will end under two conditions: either the magnetic field the coil becomes so saturated my neck if you would, can't build up anymore and then it can't couple across. Any more feedback to this side or this capacitor will basically charge up fully and it won't be able to pass more current and at that point the transistor starts turning off. The field in this coil collapses and that causes the Sim collapsing field here, which drives the transistor off decisively. So basically that means as soon as the pendulum swings past, it gives it one decisive control pulse of magnetic field just to keep it swinging as it passes as I Say this is a nice simple circuit.

It's a it's designed for Um pendulums that you start swinging yourself and it is designed by the high value of all the components to ensure the battery and this lasts a very long time. Um, so it's a nice circuit. I Shall just zoom out here because this is the point that all these little things appear on YouTube The little uh suggested next video and the subscribe to the channel type thing, but that's a nice circuit. I Do like pendulum sockets I Spent a lot of time when I was young designing them.

Um, it's worth mentioning that you can't just have the magnet hanging from string because it will kick. It needs to be just. it will kick to the side and it stops at giving the proper uh boost. It has to be a fairly solid uh stem coming down, one that can't just let the magnet lift up out the way it needs all that magnetic field to be concentrating the magnet.

so you have to have a decisive um. solid metal or plastic shaft going down to the magnet and it has to be secured to it solidly with a good Pivot Point at the top. But that is it. The super simple uh clock style magnetic pendulum swinger.

Nice circuit. Very nice indeed.