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I have very basic electronics knowledge. I'm looking to build a very simple circuit that pulls on a string which will start a pendulum swing.

I was initially thinking using of a using linear solenoid to push against a taut string but the ones I see do not have enough travel. A motor could work by winding the string but then it would need to quickly reverse direction to give the pendulum enough momentum.

Do you guys know of any components which could achieve this task? Ideally components which could be made to be silent and cheap to buy.

Would be greatful for any ideas!

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    \$\begingroup\$ Solenoid and light wire lever to multiply the travel. \$\endgroup\$
    – user16324
    Sep 24, 2020 at 13:29
  • \$\begingroup\$ Brian thanks for response. Any chance you elaborate on what you mean by "light wire lever"? I'm not sure if I've understood it completely. \$\endgroup\$
    – ML learner
    Sep 24, 2020 at 13:48
  • \$\begingroup\$ A lever made of light spring steel wire. \$\endgroup\$
    – user16324
    Sep 24, 2020 at 14:05
  • \$\begingroup\$ "I should have added that pendulum would be used to strike a surface." that sounds more like a hammer than a pendulum. Consider some sort of cam arrangement on a gearmotor such that it gets carried up into position then released by the cutout in the cam. Or replace the whole deal with some sort of electromagnet hammer. \$\endgroup\$ Sep 24, 2020 at 14:49
  • \$\begingroup\$ " pendulum would be used to strike a surface." Then add a small weight to the light lever, and use that to strike the surface. Like this. upload.wikimedia.org/wikipedia/commons/thumb/c/c1/… \$\endgroup\$
    – user16324
    Sep 24, 2020 at 14:59

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Pendulum motors were once popular for small animated retail displays. They had a permanent magnet as the pendulum weight and an electromagnet positioned to give the pendulum enough of a pull to keep it going. There was a simple switch mechanism that released the pendulum at the proper time. It should be possible to do something similar with a piece of iron rather than a permanent magnet, but a permanent magnet will likely be more effective. Search "pendulum motor."

Using a permanent magnet has the added advantage of the possibility or using magnetic repulsion rather than or in addition to attraction.

This sort of mechanism is also used in "gong" and "chime" types of doorbells. The designs for those might also be useful to investigate.

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  • \$\begingroup\$ Thank you for this! I should have added that pendulum would be used to strike a surface. I do not need it to continually swing. Would your solution work in this context? \$\endgroup\$
    – ML learner
    Sep 24, 2020 at 14:12
  • \$\begingroup\$ There is likely a way to make that work. You should be able to find specific ideas to try by searching "pendulum motor." \$\endgroup\$
    – user80875
    Sep 24, 2020 at 14:27

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