DIY membrane switch

[ignotus]

As I said in a previous post, aluminium foil isn't really a good option so I ordered some adhesive copper tape. It took ages to arrive, so I've only recently started to build a cymbal with it, but I'm now trying out another method for the edge, using a bicycle brake cable with some thread wrapped around it, which seems to work well and should be more durable. Here are a couple of pics:
First, I applied copper to the cymbal surface - this is the "ground" part of the switch so it's all connected. The 4 strips are to provide more connection points in case one fails.

switch_bottom.jpg

This is the bell switch with the top part added and held in place with some tape before putting a sheet of EVA on top.

bell_switch.jpg

And this is what the edge switch looks like:

edge_switch_cable_2.jpg

I'm still waiting to get some sheet rubber, which will go on top of this. I've done some testing with a piece I have and it seems to work well, but I can't say how it will perform in the long term - you'll have to ask again in a few months!

[ronyd]

Sorry for my confusion. In your testing step with multimeter, switch is in the open state? If so, how are the 2 foils separated enough with netting?
Also what is yhe purpose of the black covering atop of bell?

[ignotus]

Yes, the switch should be normally open until you press it. The idea of the thin netting is that it is just thick enough to separate the two sides of the switch so that a light press can close it.

Also what is yhe purpose of the black covering atop of bell?

I'm not sure I follow you. It's a (black) plastic cymbal and the copper tape is stuck onto it. It just doesn't fully cover the top of the bell area - the black bit you see is the cymbal itself.

[Nepo]

Hello Ignotus,
good Idear , exacly what I'm looking for.

I use simple no name brass cymbals, but unsuccessful piezo/piezo.
The separation is not so good and not stable.
I use a plastic cymbal too, but the metalcymbals damped with antinoisemat for carhifi are much quieter.

1. What do you think, can I use the metal cymbal as one part of the switch.
When I fix the net direct on the cymbal and the copper foil with rubber on top?

2. Works a choke on the same way , when I assemble the choke direct under the egdge switch (backsite
of the cymbal) ?

Then I have theoreticly a piezo-tip/switch-bell/switch-edge /switch-choke?

br
Nepo

[ignotus]

1. What do you think, can I use the metal cymbal as one part of the switch.
When I fix the net direct on the cymbal and the copper foil with rubber on top?

It should work, only you might have to sand the cymbal surface a bit to make it conductive; they usually have a protective coating that you might have to sand off. I was also going to use a real cymbal and do it like you're suggesting, but I didn't want to drill holes in it to pass the cables through... And as the surface is going to be covered with EVA and rubber (very silent, and aesthetically the same regardless of the cymbal you use), and as I got 14" plastic cymbals for €3.40 each, I thought it was a no-brainer. But yes, if you don't mind drilling it, a metal cymbal saves you the work of making one side of the switch.

2. Works a choke on the same way , when I assemble the choke direct under the egdge switch (backsite
of the cymbal) ?

You don't need to make another switch under the cymbal. If you squeeze the edge switch (or the bell switch even), it chokes the cymbal. See, if it just receives a short hit, it triggers an edge note, but if it is pressed for longer it sends a choke note.

I think I should point out that it might not be a good idea to apply the copper tape directly to any rubber to make the top part of the switch. The thing is, rubber flexes, but also stretches, while copper can flex somewhat but it can't stretch, so it's quite probable that over time, and with hard hits, the copper will crack and the switch will stop working. Also, and I found this out the hard way, it's damn difficult and messy to get the copper tape on a large piece of rubber in exactly the right position. You may think it's just a matter of drawing an outline of the cymbal perimeter on the rubber and then applying the copper there. Wrong. When you start sticking on the rubber, it has to contour around the bell, and suddenly the outline you drew doesn't coincide with where you thought it would... Then there are the practicalities of attaching leads for the bell and edge switches on the rubber and getting them to coincide with the holes so there aren't any lumps later... It looked good on paper but it's just too much hassle.

In short: make the switches using mylar on the cymbal and then cover it all with rubber or with whatever you choose, you'll save yourself a lot of grief; the profile of the switches is so small they will barely show through, if at all, depending on what you cover them with, and they should last longer than if you use rubber instead of mylar.

[stefan1982]

A couple of questions:
Why do you use so little copper tape? I think that if you simply cover half of the cymbal with copper tape, things will become much more reliable. Not?

I like the way you are doing this, and sharing things here. I ordered some stain white plexiglass a couple of days ago, to experiment a bit myself. The only thing I can't seem to find, a working and simple example of the wiring when you have a bell-zone (bell), bow-zone (bow sound), edge zone (crash sound) and a choke switch (choke everything).
With these switches you could easily separate the zones, although I still have no idea how to sire things up with piezo's which should tell Megadrum how hard you hit the cymbal/switches, which seems required to me.

And, what _exactly_ is EVA, and where does the letters EVA stand for, you use for the covering of the top of the cymbal?

[ignotus]

I only use a thin strip of copper around the edge because when you hit the edge, that's all you need to make contact. Same with the bell; I just cover the area I'm going to be striking. Covering half of the cymbal with copper doesn't make any sense - what about bow hits? The cymbal works like this:

- Bow hit (piezo): no switches close; MD sends bow note.
- Edge hit: Edge switch momentarily closes; MD takes velocity from bow piezo and knows it was an edge hit because this switch has a 10k resistor; MD sends edge note.
- Bell hit: Same as edge hit, only with bell switch; no resistor; MD sends bell note.
- Press edge switch: As switch is closed for longer than a hit, MD recognises it as a choke press and chokes all sounds.

This topic has diagrams explaining how to wire a piezo/switch/switch cymbal. The switches use a different design but the principle and the wiring are the same.

EVA foam: EVA stands for "Ethylene-vinyl acetate". It is used for many applications but the stuff I'm using is widely avaialble in sheets. Example. Here in Spain you can even buy it in many supermarkets in the paper and office material section. Costs less than a euro for a 50x50 cm sheet.

[Nepo]

Hello,
I saw this video and may be it is interesting for this project.
I never look inside on a comercial cymbal and was astonished about the small switchfoil that "R" use.
Looks really simple, a touch poor, but it works.

https://www.youtube.com/watch?v=RBNh_sqJyCU

br
Nepo

[airflamesred]

No product recall for them then?!

[ignotus]

Yeah, I saw that fix on the vdrums forum some time ago. Must be annoying to have to fix a cymbal that costs an arm and a leg with something as simple as a strip of tape, possibly invalidating the warranty. You'd think Roland would have sorted that out before they launched them. They'll probably just launch a "new" cymbal "with hi-tech innovations to improve bell triggering" for a few $100 more...