I have a rotary step switch (something like that: https://www.tti.com/content/ttiinc/en/apps/part-detail.html?mfrShortname=C/K&partsNumber=A20615RNCQ&customerPartNumber=&minQty=1&customerId=) that switches continuous current. I want it to send only a short pulse, like a push button would do, on two positions.

More details:

I have a ON OFF SHIM (https://shop.pimoroni.com/products/onoff-shim) to which an external push button can be connected. I would like to connect the mentioned rotary step switch there. The rotary step switch has two (12 possible) positions. Both positions should send a corresponding short pulse, like a push button.

Is this possible?

I have tried the following, but do not really get along. Especially with both positions of the rotary sending an pulse. https://electronics.stackexchange.com/a/73687


what I'm trying to do:

I have an old radio with a rotary switch to turn it on. I have replaced the inner workings with a Raspberry Pi 4. To be able to switch the Raspberry on and off properly, I have added an "On Off Shim" to it. I would like to keep the old rotary switch (or the cover) of the radio and switch the Raspberry on and off via it. I bought a rotary step switch for this purpose. I now tried to convert the continuous current to a short pulse. (like a push button wound send one). [The lenght of the pulse should be rather short, 0.5-1 sec.]

Maybe there is an even better solution?

Pi Rotary

  • \$\begingroup\$ Welcome to EE.SE. Tip: include photos so your readers don't have to follow three links to understand your question. You can leave the links there as well so the reader can find additional information. This will get a lot more readership of your question and will also ensure that your question still makes sense when the links die. \$\endgroup\$
    – Transistor
    Commented Jul 18, 2021 at 19:13
  • 2
    \$\begingroup\$ XY problem. State what you REALLY want to achieve and forget about trying to impart that information by talking about components that don't sound like they'll do the job. What do you really want to happen and state it without talking about a possible solution. \$\endgroup\$
    – Andy aka
    Commented Jul 18, 2021 at 19:18
  • \$\begingroup\$ ah, sorry, I misread before posting my answer. I concur with Andy: you might want to tell us what you actually want to implement, rather than leading us your way. \$\endgroup\$ Commented Jul 18, 2021 at 19:40
  • \$\begingroup\$ It might be done with a monostable circuit, i.e., ‘one-shot’ pulse generator, but to what purpose? How much current and voltage are needed? What pulse duration? Lighting an LED has very different requirements from operating a door solenoid or model rocket igniter. \$\endgroup\$ Commented Jul 18, 2021 at 20:07
  • \$\begingroup\$ Thanks to all. I have edited the post and added photos and my actual "real world" intended use. I hope it is clear what I want to achieve. \$\endgroup\$
    – Belgadon
    Commented Jul 18, 2021 at 20:18

1 Answer 1


PiMoRoNi don'rt seem to want to share how their power PIM shim works.

Assuming the button is read with a DC signal this should work.


simulate this circuit – Schematic created using CircuitLab

If you can spare a second pole on that switch you could try this:


simulate this circuit

  • \$\begingroup\$ Thank you for you input. I tried this and its not working. It only goes on when I turn the switch from 1 to 2 and back to 1. (or from 2 to 1 and back to 2) I used 22µF, cause I had no 1µF, but this shouldn't be problem, right? \$\endgroup\$
    – Belgadon
    Commented Jul 20, 2021 at 18:06
  • \$\begingroup\$ 22µF is probably too much, even 1µF might be too much, if you have it maybe try a smaller capacitor like 100nF or 10nF \$\endgroup\$ Commented Jul 20, 2021 at 20:42

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