Do you Understand this Circuit?

[kolias]

I’m making a pendulum clock as a hobby and I found this thread which describes a simple circuit to avoid having counterweights on my clock. I would have liked to try it but my experience in electronics is limited

https://www.instructables.com/id/Ele...etic-Pendulum/

The attached images indicate the schematic from the above link and the transistor I found in Amazon and I would like to know if the transistor is the correct one. Assuming the transistor is ok, out of the 3 terminals on it which one would be the + or - ?

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[CitizenOfDreams]

You bought the correct transistor. Here is its pinout:



Here is how the circuit works:

1. The transistor is closed (not conducting any current).
2. When the pendulum swings by the coil, it induces a voltage pulse in the first coil.
3. The voltage opens the transistor.
4. The battery current flows through the second coil and pushes the pendulum.
6. The transistor closes.
7. GOTO 1.

[kolias]

Thank you CitizenOfDreams, I don’t have the transistor yet but would it have any indication on it which is the Collector / Emitter wires?

Furthermore, perhaps a silly question but does it matter which end of the coil is the + / - side?

And finally point 1 on the schematic is positive but point 4 is negative, does it matter?

EDIT: and based on the schematic points "c" and "e" which one is the collector / emitter?

Much appreciated

[CitizenOfDreams]

1. See the picture I posted above. Look at the transistor from the front, pins pointing down. From left to right: emitter, base, collector.

2. It does matter, you may have to swap the ends of the coil to make the clock work.

3. it's probably a typo. Wire 1 would have the positive voltage when the transistor opens.

4. "C" is the collector, "E" is the emitter (pretty simple).

[kolias]

You are really Knowledgeable CitizenOfDreams, I remember you from a few years back when I posted questions about my CNC electronics

1. Looking closer at the transistor picture now it is obvious that the pins point down

2. And I thought it was a silly question but happy I placed the question, thanks

4. Now why I didn’t think about that?

Much appreciated again

[CitizenOfDreams]

Hey, it's better to ask a stupid question than to do a stupid thing because you didn't ask. You are welcome, good luck with your circuit. Please post some pictures of your project.

[kolias]

Finally I’m ready to build the Toucan clock and I bought the plans. I attach the page of the electronics for information and I have no problem on this page except on this YouTube link


another guide is building the same clock and he revised the electronics as explained below:

2N222 Transistor replaced with ZTX45 medium power NPN transistor
Using a resistor 180 ohms between SIC and Base. track 2 to Track 4
Using no Diode because: “Inductive spiking occurs when a coil (inductor) is switched on and off causing the magnetic field to collapse. The surge of power can cause connected components to fail. A diode is sometimes used to overcome the problem but in this case as the diode was on the drive coil it did not help because the problem was on the sensing coil connected to the transistor.”

Unfortunately at the end of this video he posted the schematic but it is completely out of focus and can’t read anything. Although I will have no problem building the 2 coils if I follow the video, I am asking your opinion as to which one you would have chosen between the two alternatives I have (the one I purchase or the one from the video)

[joeavaerage]

Hi,
that circuit looks very much like an astable blocking oscillator.....is that what its supposed to do?

I've used them as both astables and monostble and are great for producing very short, well defined pulses.
If it is a blocking oscillator then you will need some emitter degeneration resistance, and, depending
on whether you want monostable (triggered) or astable (free running) then you need some base bias supply.

My go to is C.A. Holt, Electronic Circuits, Digital and Analogue, Wiley & Sons First Ed, Section 22-5 page 758.
Analysis by LTSpice is also very useful.

If this is a blocking oscillator you should try to achieve very good coupling between the coils, a K of 0.95 is good. Poor coupling
and/or excessive turns ratio all make them harder to design and build to run reliably.

Nothing turns a BJT off faster than regenerative feedback and using even fairly slow BJTs can result in pulse durations of less than 1us and still
have great pulse shape.

Craig

[kolias]

Hey Craig

I only try to build as a hobby a wooden clock, I know almost nothing about electronics and that’s why I post here for help. My question is which of the 2 circuits is better.

[joeavaerage]

Hi,
then what is the circuit supposed to do?

Craig

[ZASto]

Craig,
take a look at this one, and substitute the toy with pendulum (instead a constant force spring / weight on the string).


BUT!
Clock needs a driving force to turn the gears so...

[kolias]

Based on the video shown in my post #7, I made the attached wiring schematic. Is it possible someone with experience to tell me if the schematic is correct?

[joeavaerage]

Hi,
I still don't know what it is that the circuit does?. If its a blocking oscillator you need some resistance in the emitter lead.

Craig

[kolias]

Craig I don’t understand why you don’t know what the circuit does.

ZASto in post #11 explained very well and the video in my post #7 also explains in details what the circuit does and how it is built

[joeavaerage]

Hi,
I was at work at he time and was only able to see the first minute or so, and without sound at that.

The video explains it perfectly, and include the diode.

Its way less sophisticated than a blocking oscillator which I use to trigger the gates of thyristor bridges.

Craig

[kolias]

Hey, it's better to ask a stupid question than to do a stupid thing because you didn't ask. You are welcome, good luck with your circuit. Please post some pictures of your project.

Finally I got this project done. Making the electromagnet which drives the clock was much easier than I thought. The plans to make the clock were purchased from Clayton Boyer. Thanks for the help

[CitizenOfDreams]

Looks nice, thanks for reporting your progress!

[Al_The_Man]

Nice job, here is a good second project !

[kolias]

Nice job, here is a good second project !

Thanks Al for the video, I can only hear the video but there is nothing to see, just a solid green screen. Even in YouTube there is only a green screen. if you have a better link I would love to see what this guy built.

[Al_The_Man]

I only have the Youtube link which works for me?
Here is the link, replace the yt with youtube

https://www.yt.com/watch?v=laJX0txJc6M