In India, on certain social festivals like Durga Puja, Kali puja etc, lighting decorations are done around roads etc, where various themes or stories are animated (such as stories from Aesop's fables), using a complex array of chaser light techniques.

Nowadays these chaser effects are done on LED lights using sequence generator chips or ICs. Back when I was a kid, say in the early 90's, the task was done in an entirely different way. There was a big motor (usually a ceiling fan motor) attached with a drum-like structure, and there were and some carbon brushes connected with that drum looked somewhat like this:

enter image description here

When the drum revolved, the unevenly placed conductive plates touched the carbon brushes at a different time-period, it resulted in switching on associated light series. I still can see in my mind's eye the falling sparks from the carbon brushes.

But unfortunately after web crawl through several years I couldn't found a single blog mentioning this vintage lighting technique. When I ask people in person, I see most people forgot it or may be they never noticed it. The laypeople who sewed the stories on iron grids were mostly uneducated poor people, seemingly blogging was not possible for them. I wonder how a wildly popular technique can just be forgotten.

My question is:

Is there a name for this mechanical sequence generation technique?

Prior research

I have thoroughly searched wikipedia and other internet websites.

I also asked my dad who told me the "drum" like portion were probably a bit more complicated than this, containing some gears that reduces the speed of switching. I found some blogs that mention use of relay switch as a sequence generator, but I really did not find any mention of motors as sequence generators.

Confession and request

Our family got our first camera in around 2007 (which was a Kodak film camera,) when this lighting technique was already obsoleted, so we do not have any photographs of this technique. If anybody has a picture of this technique, please add the photograph and a permission to reuse.

See also:

Modern day version (LED based) of such lightings:

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    \$\begingroup\$ Some early digital clocks used a similar method. A motor drove gears which had drums with brush contacts that switched power to the clock segment lights. In the late 70s someone asked me to see why his clock segments weren't always working, I was astonished to find a mechanical mechanism inside. \$\endgroup\$
    – Mattman944
    Dec 9 '20 at 18:02
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    \$\begingroup\$ @Mattman944 Such clocks with electromechanical action are still commonly available as novelty items e.g. amazon.com/Betus-Retro-Style-Shelf-Clock/dp/B06XR8VTF9 \$\endgroup\$
    – Reinderien
    Dec 9 '20 at 18:17
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    \$\begingroup\$ @Reinderien, That "flip card" mechanism is a different thing altogether. The clock that Mattman944 is talking about would have had a lighted, 7-segment display—just like a modern, electronic clock might have—but the lighted segments were switched on and off by mechanical means. \$\endgroup\$ Dec 9 '20 at 19:34

Yes - a cam timer:


I'm not sure what other detail you're looking for.

  • \$\begingroup\$ Yes... much like this. maybe our version looked a bit more crude and DIY-style however. \$\endgroup\$ Dec 9 '20 at 17:58
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    \$\begingroup\$ The version you're thinking of probably differs from the one depicted in Wikipedia, because it is entirely mechanical (using rotary-position "bumps") whereas yours sounds more like the way a potentiometer is built but with multiple arcs. \$\endgroup\$
    – Reinderien
    Dec 9 '20 at 18:00
  • \$\begingroup\$ Yes, our version seem to be potentiometer type because sparks appeared on the drum (and sometimes sparks fallen from the drum). \$\endgroup\$ Dec 9 '20 at 18:37
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    \$\begingroup\$ You may still be able to build one by modifying a brushed motor's carbon commutation ring, if you can manage to score the ring without totally breaking it. \$\endgroup\$
    – Reinderien
    Dec 9 '20 at 18:42
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    \$\begingroup\$ @Reinderien: I expect the machines were rather more primitive than you think. Imagine a metal drum driven by a washing machine motor. There insulated patches and bare patches on the drum, and the brushes just touch bare metal - and are probably just metal strips themselves. The whole thing out in the open, and at line voltage as well. \$\endgroup\$
    – JRE
    Dec 9 '20 at 19:34

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