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Any ideas - Rotary momentary switch?

Discussion in 'General Electronics Discussion' started by rockrockmcrock, Sep 11, 2016.

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  1. rockrockmcrock

    rockrockmcrock

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    Dec 19, 2011
    So I'm converting a non functioning 12v old 60s radio to mp3 and Bluetooth. The challenge I have set myself is to maintain the exterior completely and hide all the modern controls by using as many of the existing knobs as possible.

    To save time I've bought an OTS mp3 board and decided to only build the amp myself. The modern mp3 board uses push button momentary switches for FF & RWD. The old radio has 2 rotary knobs - I'd like to make use of one for FF and RWD. I could do this if I could find a 2 way momentary rotary switch off the right size.

    All the rotary momentary switches I've found so far are 240/110v massive types that are too large for the application which needs a standard 15-20mm with 6mm shaft 12v type. Any ideas where I can find one? Or is there a better way to do this?

    Chris guys - all thoughts welcome!
     
  2. Alec_t

    Alec_t

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  3. rockrockmcrock

    rockrockmcrock

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    Dec 19, 2011
    Perfect size - I just don't think it's momentary, at least I can't find any info saying that. It's the momentary (spring return) I'm looking for - you know like an ignition switch has just with 3 positions not 2.
     
  4. Alec_t

    Alec_t

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    I'd bet not momentary. If it were me I'd probably find a way to attach a spring to bias it to the centre position :D.
     
  5. duke37

    duke37

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    One way, perhaps a bit inconvenient, is to place some reed relays inside the cabinet and use a hand held magnet to activate them.

    Are you going to get the old radio working, at least for the sound output?
     
  6. rockrockmcrock

    rockrockmcrock

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    Dec 19, 2011
    That was the plan so If I can I'm going to reuse the amp circuit, but having opened it up I'm not hopeful as it's quite clearly been subjected to some water (or coffee/tea) damage inside from the top. Outside was fine though - go figure!

    On the momentary switch one possible work around I was thinking of was a couple of lever arm momentary buttons and a spring clip - but that's not ideal! I can't believe there isn't a momentary rotary out there that isn't a 240v breaker - it's mad!
     
  7. Bluejets

    Bluejets

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    If you have the room internally , one could arrange the rotary switch to operate mini relays on a momentry basis.
    Use the clean contacts in you main circuit.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    How about a rotary encoder?
     
  9. rockrockmcrock

    rockrockmcrock

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    Dec 19, 2011
    @Blue - not a bad idea thanks, but I'd lose the long press action. Still if nothing else works that might be the only way forward

    @Steve - it did cross my mind but had 2 issues: 1 finding an encoder with a long shaft and at the right size (usually they're small pcb mount types); 2 I'd have to start messing with coding, not an issue skills-wise but I blew my Pic2 kit earlier this year so I really wanted this project to be simple and cheap.
     
  10. Alec_t

    Alec_t

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    How about one of these (albeit a tilt/push action rather than rotary)?
     
  11. Externet

    Externet

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  12. rockrockmcrock

    rockrockmcrock

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    Dec 19, 2011
    @alec - like that! Not for this project as the knobs are inset, but for others that's a classic piece of kit - a sort of micro joystick!

    @Externet - now that's lateral thinking - the Amazon link is too big bit I have smaller ones in my Ford that would fit. However the 3 pole and lever arm is a great alternative. I'm thinking a 3 pole sprung toggle (or even 2 momentary spring toggles) may work well and provide the spring bias around centre. Ok I'd have to make it but as ideas go that's the best so far if I can't find an OTS rotary.
     
  13. rockrockmcrock

    rockrockmcrock

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    Dec 19, 2011
    Darn - just checked the knobs in my motor and they're not sprung :-( so so far the spring momentary SPDT toggle and a pushrod is looking the best option
     
    Last edited: Sep 12, 2016
  14. Externet

    Externet

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    If you put a lobe on the original shaft, and 2 of these...

    ----> http://www.cadsample.com/wp-content...sition-Microswitch-3D-Solidworks-Drawings.jpg

    Action set for partial lobe rise will produce return-to-center when released.

    There is also this kind of switches that an eccentric lobe on the shaft can do the desired action

    ----> http://www.cadsample.com/wp-content...sition-Microswitch-3D-Solidworks-Drawings.jpg

    Or, a magnet on the shaft and two reed switches... Explore joystick mechanisms too.
    Your switch does exist out there. Just matter of coinciding your search with the correct terminology for it.
     
  15. jobc

    jobc

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    Sep 15, 2016
  16. rockrockmcrock

    rockrockmcrock

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    Dec 19, 2011
    Well that worked brilliantly - great idea those lever arms - just took a few boards/screws, some bridging compound and a washer. see below and thanks guys!

    IMAG1084_1.jpg IMAG1085_1.jpg
     
    Externet and (*steve*) like this.
  17. Alec_t

    Alec_t

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    Nice one!
     
  18. BobK

    BobK

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    Holy Mother of Invention!

    Bob
     
    rockrockmcrock likes this.
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