diy switches

[therecordingart]

those are bad ass how do they work?

I assume you are talking to me. I'm planning on writing an article so people can build their own "T.T.G. style" touch plates as they are really easy and cheap to build. Its one of the things I'm going to give away.

The short version is there is a set of screws under the plate that are isolated from the case which are wired for a logic high signal. These are contact points. You can see a few under the plates in the angled picture. The plate float above the contact points connected to the case by the screws on the plate corners. The plate is grounded. The plate is pushed up away from the points using force resistant material which can be foam, rubber, spring, etc. When you depress the plate compressing the resist material in the centre of the plate contact will be made with one of the screw contact points thus your connection. It is essentially a single moving part SPST NO actuator.

I love them. I've used them for years and I am known for destroying regular footswitches. I haven't had a failure yet.

Andrew

I can't friggin' wait!

[R.G.]

I recently tried the Boss bypass circuit without the buffers and I was very pleased with the result. The off resistance of the fet is big enough for this purpose.

See the "Clinton Bypass", Geofex. "I don't think you can find evidence that it's not true."

I have to figure out how to re-arrange the circuit to send the input of the fx to gnd when bypassed.

Use a P-channel JFET.

It's kind of like the guitar itself. It's been said that the guitar is the easiest of all instruments to play badly, and one of the hardest to play well.

Nop. Violin 

It is easier to play guitar badly - you don't need a bow. But violin is well into the group of hardest to play well.

[R.G.]

The short version is there is a set of screws under the plate that are isolated from the case which are wired for a logic high signal. These are contact points.

This is one of those places where a microswitch works well too. Make the actuator of the microswitch protrude through a hole in the case. The insulation is all in the microswitch, no need to insulate the screw points. This kind of thing is, as I mentioned, what microswitches are intended for.

[The Tone God]

Hey Andrew, your Fuzz box looks killer. how did you do the screw-switches??

Are you talking about the touch points controls ? They're capacitive sensing. Right now not very DIY-able as most of the magic is in the microcontroller.

This is one of those places where a microswitch works well too. Make the actuator of the microswitch protrude through a hole in the case. The insulation is all in the microswitch, no need to insulate the screw points. This kind of thing is, as I mentioned, what microswitches are intended for.

Yes you can use a microswitch if you want. With that though you have mount the switch which can be difficult and as good as microswitches are it is a possible failure point. Fewer moving parts means fewer failures so adding a microswitch which has multiple parts internally is adding unneeded complexity. By turning the actuator into the switch contact you only have one moving part. Isolating the screw from the case is not that hard with the right hardware and it costs less then the microswitch would. If there is a failure it is easy to repair.

Another point which probably applies more to me as a manufacture then the DIY hobbyist is the contact screw points also serve as mounting points for the circuit board so no need to come up with some mounting schem for the board. Since the board is mounted to the contact points by running connections to the board mounting holes all the wiring is done on the board. No need for extra manual wiring. Just drop the board in and tighten the nuts. Clean, easy, fast, cheap.

Andrew

[R.G.]

Yes you can use a microswitch if you want. With that though you have mount the switch which can be difficult and as good as microswitches are it is a possible failure point. Fewer moving parts means fewer failures so adding a microswitch which has multiple parts internally is adding unneeded complexity. By turning the actuator into the switch contact you only have one moving part. Isolating the screw from the case is not that hard with the right hardware and it costs less then the microswitch would. If there is a failure it is easy to repair.

To each his own. One man's fish is another man's poisson.

[mac]

I have to figure out how to re-arrange the circuit to send the input of the fx to gnd when bypassed.

Use a P-channel JFET.

Thx!

mac

[tysonlt]

To each his own. One man's fish is another man's poisson.

LOL, I got it, R.G!

[tysonlt]

Hey Andrew,

I think your touch plates might be what I need for my midi controller project. I want to have 30+ switches so a cheaper alternative would be great. These plates sound so simple!

A couple of questions:

1) If I understand correctly, there are two screws that are wired as a simple SPST momentary contact? I would wire this directly to my PIC.

2) Does the plate have to be large enough to flex in the middle? I would want it to be much smaller than the ones shown (beer-cap sized!)

3) Pardon my mechanical ignorance, but if the plate is screwed down at the corners, how does the plate get depressed? OR are the holes big enough for the plate to move over the screw shaft?

THANKS!!! This could be a great solution for me to build my midi controller under budget!

[tempus]

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.

[tysonlt]

Hey, thanks for that input. Sounds nice and simple. So I guess you didn't have to cut a hole in the mousepad at all, just sit the 'pancake' on top of a microswitch?

My application is a midi pedal board with lots of switches. I want 20-30 switches but need to keep costs down.

Based on your idea, I am thinking of maybe having a microswitch just barely poking out of a hole in the board's chassis, and then just glue a foam square on it with a hard plastic layer on that. Reckon that would work?

[amptramp]

There used to be a number of capacitive touch plate controls based on the touch plate being connected to the resonant LC circuit of an oscillator.  When the plate was touched, the load stopped the oscillator and therefore reduced the bias, allowing a relay in the plate circuit to pull in.  Many were built based on a 117L7GT and the Miller 695 capacitive relay coil.  You really don't need anything that big.  If you want multiple switches, have a single oscillator and an amplifier for each switch that is detuned and loses bias, causing more current drain.  You could afford to do an entire touch keyboard this way.

[tysonlt]

Sounds interesting, and frightening! :-) that's probably a bit beyond my ability at the moment. Besides I need to push it with my feet.

[tempus]

Hey, thanks for that input. Sounds nice and simple. So I guess you didn't have to cut a hole in the mousepad at all, just sit the 'pancake' on top of a microswitch?

My application is a midi pedal board with lots of switches. I want 20-30 switches but need to keep costs down.

Based on your idea, I am thinking of maybe having a microswitch just barely poking out of a hole in the board's chassis, and then just glue a foam square on it with a hard plastic layer on that. Reckon that would work?

Right - no hole in the mousepad, and what you're thinking is exactly what I did - the microswitch was mounted just below the chassis surface and protruded through just enough to be pushed. You have to test it a bit to make sure you don't have them too close because you can (and I did on 1 switch) squash and break them. You also need to make sure they aren't too far from the surface or they won't click. It really wasn't hard nor did it take too long to do, and it literally cost me nothing to build them (and not a lot of time either). The mousepad was something I had lying around from when I used to have a ball mouse and was of no more use to me, the melamine was free sampled, and the switches were pulled from old garbage electronics.

I don't know how fancy a setup you have, but if you're etching a board, you could solder the switches to the board and mount the board below the surface with spacers. I should also mention that I only ever had to replace or reset one switch (or maybe 2..) out of the 15 that I had on the board, and my mounting setup sucked. It was very reliable, so with only a little more effort and forethought that I put into it, you should be able to get something pretty solid.

[DavenPaget]

If you're going digital , hall effect sensors are the way to go .
http://singapore.rs-online.com/web/p/hall-effect-sensors/1811479/
And a "touch" plate with a weak magnet spaced far enough so the sensor doesn't sense the magnet normally , and just use it as a momentary switch , switched by CMOS ,
http://www.thetonegod.com/tech/switches/switches.html under flip-flop momentary . This way reliability issues ? 0 .

[tysonlt]

Looks interesting, but they are still a couple of aussie dollars each. My main goal is to make it cheap enough to use 30-40 of them.

[DavenPaget]

Looks interesting, but they are still a couple of aussie dollars each. My main goal is to make it cheap enough to use 30-40 of them.

They are for reliability sake , something TTG/Andrew will appreciate 
As for you bottle caps and latching tactile switches makes sense .

[tysonlt]

At that, I could just glue a coke bottle cap onto the shaft of a push-button switch... the bottle hitting the chassis would prevent excessive travel on the switch.

One of these:

http://taydaelectronics.com/media/catalog/product/cache/1/image/500x/9df78eab33525d08d6e5fb8d27136e95/T/C/TC-A0109-X_3.jpg

with one of these:

http://en.wikipedia.org/wiki/File:Plastic_Bottle_Cap.JPG

[DavenPaget]

At that, I could just glue a coke bottle cap onto the shaft of a push-button switch... the bottle hitting the chassis would prevent excessive travel on the switch.

One of these:

http://taydaelectronics.com/media/catalog/product/cache/1/image/500x/9df78eab33525d08d6e5fb8d27136e95/T/C/TC-A0109-X_3.jpg

with one of these:

http://en.wikipedia.org/wiki/File:Plastic_Bottle_Cap.JPG

Just remember to flush them , nobody wants to see a bottle cap on the outside 
( I.E : A hole saw and some deburring or a unibit .)

[tysonlt]

Just remember to flush them , nobody wants to see a bottle cap on the outside 
( I.E : A hole saw and some deburring or a unibit .)

OK!

... Now you'll have to explain what you mean, I'm not so familiar with the hardware side!

Do you mean make them flush with the chassis?

[DavenPaget]

Just remember to flush them , nobody wants to see a bottle cap on the outside 
( I.E : A hole saw and some deburring or a unibit .)

OK!

... Now you'll have to explain what you mean, I'm not so familiar with the hardware side!

Do you mean make them flush with the chassis?

The cap should be slightly poking out , sorry , not flush .