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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

Edit:

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

Belgadon
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  • 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. – Transistor Jul 18 '21 at 19:13
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    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. – Andy aka Jul 18 '21 at 19:18
  • 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. – Marcus Müller Jul 18 '21 at 19:40
  • 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. – DrMoishe Pippik Jul 18 '21 at 20:07
  • 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. – Belgadon Jul 18 '21 at 20:18
  • What is that pulse going to do? If it is an on/off function to replace the original on/off switch of the radio you can accomplish that with a relay or even a replacement volume control that has the switch assembly on it. Are the electronics powered, I believe the "shim" needs power. to operate, am I correct? – Gil Jul 18 '21 at 21:12
  • Thank you @Gil. Apart from the cover, nothing remains of the old radio. The shim offers a button for switching on or shutting down the Raspberry Pie. It also has the option of connecting an external button. (first picture, top left, where it says "BTN"). I would like to connect a rotary switch that "emulates" the push-button. The shim does not react to a switch that supplies permanent current, but only to the impulse of a push-button. The two positions of the rotary switch should each send a short pulse. As if someone pressed a button Yes, the shim is powered via a micro USB connection. – Belgadon Jul 19 '21 at 04:50

1 Answers1

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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.

schematic

simulate this circuit – Schematic created using CircuitLab

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

schematic

simulate this circuit

Jasen Слава Україні
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  • 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? – Belgadon Jul 20 '21 at 18:06
  • 22µF is probably too much, even 1µF might be too much, if you have it maybe try a smaller capacitor like 100nF or 10nF – Jasen Слава Україні Jul 20 '21 at 20:42