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# Thread: Do you Understand this Circuit?

1. ## Do you Understand this Circuit?

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 - ?

2. ## Re: Do you Understand this Circuit?

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.

3. ## Re: Do you Understand this Circuit?

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

4. ## Re: Do you Understand this Circuit?

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).

5. ## Re: Do you Understand this Circuit?

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

6. ## Re: Do you Understand this Circuit?

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