Name for a plunger resistor that mimics a tactile switch


#1

Hello. I’m trying to find what looks like a tactile switch but is actually a resistor. These are buttons for certain versions of the Omnichord '80s synth toy. I’m attaching a picture, they look like tactile switches.

Is there a name for this? If I had a better sense of how to search, I might come up with an option.

They read about 10k resistance or less when pressed, which triggers a note. They are variable resistors in the sense that if you push harder, they provide less resistance… but functionally, the synth treats all triggered presses the same.

Thanks!
Zack


#2

Hello,
Unfortunately after looking through all of our options it appears we don’t carry that switch. Unfortunately there is no easy way to search for that specific switch without some markings on it. Possibly using the dimensions might help you with your search. Sometimes they are called by their length and width dimensions, or the one dimension if it is a square.


#3

Thanks. But so I’m clear, this is not a switch in the literal on/off sense. It performs as a resistor.

I can find a switch by searching for dimensions, yes. But I’m trying to find out if there’s a resistor part I should be searching for.


#4

Hello,
You haven’t really explained what the resistance and or switch is doing. Like, for having a switch function, is there an open and closed state? Also, is it a fixed resistance, does it actually vary from 0-10k, or what are the values? From how you have described it, it sounds like a switch with a built in 10k resistor. Which, if it is you may be able to locate a switch, and then add a 10K resistor in series. That is what I went by when searching. Unfortunately we don’t have a switch with a built in 10k resistor, or a potentiometer that uses a plunger action.


#5

Hi Andy
Okay, thanks, the end of your note, “a potentiometer with plunger action” cuts to the wording I could have used earlier. So I think I’m at an impasse.

These plungers are actually variable in resistance. If you push hard, you can get them down to 1k ohm or so. But they have a natural distance they move without a lot of force, and that reads about 10k.

Functionally, I like your idea of a switch and a fixed resistor. I was hoping this kind of weird button existed still, but it sounds like they don’t.

Thanks.

Zack


#6

The pressure-dependent character of the the measured contact resistance suggests the possibility of a carbon or conductive polymer contact element, rather than the metal contacts found in most general-purpose switches.

Such a thing probably would have been relatively inexpensive to manufacture and acoustically quieter in operation than a small tactile switch, and thus a very reasonable choice for the stated application. If it’s simply triggering logic, I’d guess that a the effective contact resistance is not critical and that a standard tactile switch that’s mechanically compatible would also work electrically. It’s conceivable though that the higher contact resistance of the OEM switches was leveraged as the R in an RC filter to de-bounce the inputs, in which case the prior suggestion of adding a series resistor should help.


#7

Thanks for your thoughts. Yeah, I was hoping to find new parts to replace just one or a few… In this case, I had a parts machine to pull a few good ones. But I’m running out of those.

If I come across a similar situation where it makes the most sense to replace them all–so they all feel the same in the end–I like the idea of simple tactile switches with resistors.


#8

Hi Zack,

Maybe the schematics could help in identifying the switches.
Check the website:
http://www.suzukimusic.co.uk/omnichord-heaven/service/schematics.html

Cheers,
heke++


#9

Thanks, Heke. Yeah, I’ve been though details over there but I’ll take another look in case I missed something.

My sense is that these weird switches are long gone. I had some extras here from another Omnichord I was able to use. But if it comes up again, replacing them all might be worth it.


#10

Hi Zack,

That switch could be made by ALPS.
This model could perhaps come close:
https://www.alps.com/prod/info/E/HTML/Tact/SnapIn/SKEG/SKEGAEA010.html

Cheers,
heke++


#11

HI Heke, that is very possible, unfortunately, we do not carry Alps products so we would not know. There is not much else we can add to this posting, the previous information from Rick, Andy and Zack is the best we have on this switch. Glenda


#12

Wow, thanks. That very well could be it. I’m past my need now but I’ll check it out in the future if I’m working on another Omnichord with the same switches. (Other models used different switches.)