Poor man's microswitch actuator

[tysonlt]

Hi Esteemed Legends,

I want to design a 'poor man's' actuator for a microswitch. I am planning to build a midi controller with footswitches for patches and lots of instant access switches dedicated to analog loops, amp channels, etc. These switches would interface to a microcontroller and would not carry the guitar signal. The design I have in mind uses about 40 switches!

To keep cost down I want to use microswitches, so the challenge is to build a cost-effective actuator. These ones are good, http://www.smallbearelec.com/Detail.bok?no=32, but to buy enough would still be a fair chunk of my rather paltry budget.

One idea I have is a modification of the ingenious pancake switch. My idea is to have a microswitch shaft poking just out of the chassis hole, and sit a beer bottle cap on a small ring of flexible foam. Image:

http://imagepaste.nullnetwork.net/viewimage.php?id=3048

The blue bit would be a donut-like ring of foam that sits around the hole where the switch pokes out. I figure that if you press the switch hard enough the beer cap will compress the foam enough to hit the switch, but the cap hitting the chassis will prevent excessive travel and preserve the microswitch.

Does this sound feasible? Do any experienced people see any major gotchas to this approach? My main concern is finding a glue that will keep the foam attached to both the chassis and the beer cap. Maybe I could put two small bolts through the beer cap down to a nut under the chassis. The nut would stop the cap from coming off, but would still allow downward force. A picture!

http://imagepaste.nullnetwork.net/viewimage.php?id=3049

I was a programmer for a number of years so programming the pic will be ok for me. It's the hardware that I need guidance with!

Thanks for your help, and thanks for letting me think out loud. It helps.

Oh, and Happy New Year, everyone! My resolution is to build this midi controller before the world ends this December!

[PRR]

> uses about 40 switches!

PC keyboard with custom markings.

You surely have enough horsepower in a PIC to decode keyboard serial to one-of-88 code, and you'll surely think of 40+ more functions. You can get mini-keyboards for ~~$10.

I'm assuming 40 bottlecaps is finger-operated. 40 bottlecaps spaced far enough apart to foot-switch may be a lot of area.

[tysonlt]

Hi PRR,

Thanks for the reply!

Yes a keyboard would be fine for hands, but believe it or not it is for feet... 40 includes 10 patches, 15+ instant access, banks, some mutes, amp controls, a tap, and spares. It would fit in a rack tray sized box.

I figure if I'm custom building one I might as well put lots of buttons on it. Reprogramming a PIC is easier than expanding the hardware later.

The other idea is to use lever-actuated microswitches and use a small door hinge with a spring under it... That might work too!

[tempus]

Check out http://www.diystompboxes.com/smfforum/index.php?topic=91786.0

Here's my suggestion:

My 1st pedalboard used a variation on the touch plates, but were nowhere near as cool. I took a piece of melamine (you know that stuff they make countertops and certain Martin guitars out of?). If you ask them at a hardware store or anywhere they sell/build countertops, they will probably give you some of the little rectangle sample cards they have (at least that's what I used). Glue this to a same sized piece of a mouse pad (mine were about 1.5" square). If you're a garbage collector like myself, you'll have old VCRs, stereos, etc, that all use these little momentary contact switches. Salvage one of those and mount it underneath the mouse pad, so that when you push down on the 'switch', you compress the mouse pad a little, thus making safe (IOW it's pretty hard to smush the switch itself to its breaking point with the mouse pad in there) and positive compression of the momentary contact switch. It's kind of like RGs pancake switches only cheaper.

Now, I don't know what kind of surface you're putting the switch on, so you'll have to do a little thinking to figure out how to reliably mount the whole thing to the surface you're going to stomp on.

[R.G.]

for reference:
http://geofex.com/Article_Folders/footswitch_pancake/footswitch_pancake.htm

[tysonlt]

Having a lively conversation over in this thread, suggest moving:

http://www.diystompboxes.com/smfforum/index.php?topic=91786.0