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  1. #1
    Join Date
    May 2009
    Posts
    1326

    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 - ?
    Attached Thumbnails Attached Thumbnails Clock Circuit.JPG   Clock NPN Transistor.jpg  
    Nicolas

  2. #2
    Join Date
    Nov 2012
    Posts
    1267

    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. #3
    Join Date
    May 2009
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    1326

    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
    Nicolas

  4. #4
    Join Date
    Nov 2012
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    1267

    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. #5
    Join Date
    May 2009
    Posts
    1326

    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
    Nicolas

  6. #6
    Join Date
    Nov 2012
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    1267

    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.

  7. #7
    Join Date
    May 2009
    Posts
    1326

    Re: Do you Understand this Circuit?

    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)
    Attached Thumbnails Attached Thumbnails img085.jpg  
    Nicolas

  8. #8
    Join Date
    Nov 2013
    Posts
    4280

    Re: Do you Understand this Circuit?

    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

  9. #9
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    May 2009
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    1326

    Re: Do you Understand this Circuit?

    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.
    Nicolas

  10. #10
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    Nov 2013
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    4280

    Re: Do you Understand this Circuit?

    Hi,
    then what is the circuit supposed to do?

    Craig

  11. #11
    Join Date
    Apr 2005
    Posts
    304

    Re: Do you Understand this Circuit?

    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...
    Make no mistake between my personality and my attitude.
    My personality is who I am. My attitude depends on who you are.

  12. #12
    Join Date
    May 2009
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    1326

    Re: Do you Understand this Circuit?

    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?
    Nicolas

  13. #13
    Join Date
    Nov 2013
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    4280

    Re: Do you Understand this Circuit?

    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

  14. #14
    Join Date
    May 2009
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    1326

    Re: Do you Understand this Circuit?

    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
    Nicolas

  15. #15
    Join Date
    Nov 2013
    Posts
    4280

    Re: Do you Understand this Circuit?

    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

  16. #16
    Join Date
    May 2009
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    1326

    Re: Do you Understand this Circuit?

    Quote Originally Posted by CitizenOfDreams View Post
    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.
    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
    Nicolas

  17. #17
    Join Date
    Nov 2012
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    1267

    Re: Do you Understand this Circuit?

    Looks nice, thanks for reporting your progress!

  18. #18
    Join Date
    Dec 2003
    Posts
    24216

    Re: Do you Understand this Circuit?

    Nice job, here is a good second project !

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  19. #19
    Join Date
    May 2009
    Posts
    1326

    Re: Do you Understand this Circuit?

    Quote Originally Posted by Al_The_Man View Post
    Nice job, here is a good second project !
    https://www.youtube.com/watch?v=laJX0txJc6M
    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.
    Nicolas

  20. #20
    Join Date
    Dec 2003
    Posts
    24216

    Re: Do you Understand this Circuit?

    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
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

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