Touch button

Design Concepts
1

Sorry if this is mentioned in forum threads before, feel free to hammer me down if so ;).

First, my only knowledge about touch sensors comes from this vid and his website:

http://pcbheaven.com/circuitpages/PIC_Frequency_Change_Touch_Button/

I saw the video, and I got the urge to replace some of my tact switches on my not-finished mb64e. That type of switches would suit my usage much better than normal tact. switches. In fact I was thinking about it prior to stumbling across this video - that I need some sort of stable button concept for my box with a larger surface than the typical tact switch with a knob. -> A setup of buttons that can be operated without precision working fingers and have a very light touch threshold - and it doesn’t get lighter than a capacitive touch sensor :).

My thought was to use a dedicated MCU for sensing, and then output that to DIN on the PIC. Maybe even if I get deep in it -> is it possible to make use of some sort of bus com. between the two MCUs…? I have no idea, as I have about zero experience in MCU coding, and what the different ones can do.

My question then is - some of you is bound to know something about this shit - can I make several touch sensors like the one in the video (just a dual side PCB or a single side with two regions) and place them under the same piece of plexiglass and still operate them in a stable manner. Of course the sensitivity must be tweaked so that it doesn’t start acting as a proximity sensor instead. Will multiple of these sensors work under the same plastic (or whatever) surface?

This seems as a bit of work to set up, but it would be a nice alternative to the traditional knobs where u don’t need (or don’t at all want) the tactile feeling.

For example - you could make those PCB sensors, put them under an equal sized plexiglass - illuminate the plexiglass, and then put a thin piece of plexi over that again with your desired graphics work etc… Fantasy working now.

Any input would be cool.

I could build a test setup myself using analog components like in one of his vids, but if someone of you has experience with touch-stuff it would be cooler to know something before I build it and not after I build it and it doesn’t work as expected :).

What do ya say? :slight_smile:

2

Something like this:

A little crude looking that one, but this illustrates pretty well what I had in mind.

If u use seperate pieces of plexi over the sensor and with one piece of plexi with graphic work on top of that, u could illuminate the buttons with different color / seperate on/off without too much color bleed too :).

This is definetly a thing I’m gonna explore deeper!

3

I’ve some good news for you: the PIC based MIOS already supports capacitive sensors, there is no need for an additional chip! :slight_smile:

Circuit: http://www.ucapps.de/mbhp/mbhp_din_touchsensors.pdf

The MB64E firmware even has a special menu page which allows to set the touchsensor sensitivity

Best Regards, Thorsten.

P.S.: note that touchsensors are not supported by MIO32, since it would stall the firmware execution too much (CPU is running much faster -> more CPU cycles consumed -> worse performance)

4

Haha T, I didn’t even consider that possibility now, but when u mention it I can remember something way back in my mind that I have read something about it, but I think it’s a long time ago. But as I stated (and shown to be true)

some of you is bound to know something about this shit

:).

It may be a fast way to implement this in my 64E.

I will definetly take a dive into the technical aspect of this. I found this topic extremely interesting, and studying this may lead me towards some other cool stuff too.

And for MIOS32, I gather there are no plans for implementing this here. In that case, a dedicated mcu would do the job, yeah? It would be interesting for me to do a proof of concept thing on this - to learn more about MCU programming, making the sensors, and details in the capacitive sensor technology. Now, I don’t know much about communication between MCUs, and much less I know about that stuff when it comes to doing it with mb apps, but is it possible to use the extra mcu and communicate button press through a databus (but not directly implemented in mios mcu), or do it have to be a MCU that converts the touch to a digital output, and interface that to mios MCU? a pretty simple way to do it (when it comes to understand how it works) but “extremely” complicated hardware wise :stuck_out_tongue: