Design experience with rubber switches?

[Joerg]

Hello Folks,

A while ago I asked about cheap tact switches. I found that none of the
usual ones works well for handheld gear if you don't want to have an
extra cap. Plus they don't come in round to avoid enclosure milling.
After asking the same question in a German forum one of the guys there
(Gunther Mannigel) suggested these:

http://www.ittcannon.com/media/pdf/catalogs/e22.23.pdf

These are arrays of 36 rubber switches that can be cut into individual
switches, or selectively cut to make a semi-custom keyboard array if
desired. The really good news is that they come in round, allowing
simple drilling of an enclosure to accommodate a switch.

At Arrow they list for just under $10/36 which comes to about
25c/switch. Right on BOM budget. Sweet. But: There is scant information
about these, no app notes, no recommended drill patterns, thicknesses,
etc. IOW, nada.

The rep promised me a file with recommended land patterns. My question:
Has anyone designed with stuff like this? Share experiences? Are there
other large manufacturers?

Regards, Joerg

 

[John Larkin]

Hello Folks,

A while ago I asked about cheap tact switches. I found that none of the
usual ones works well for handheld gear if you don't want to have an
extra cap. Plus they don't come in round to avoid enclosure milling.
After asking the same question in a German forum one of the guys there
(Gunther Mannigel) suggested these:

http://www.ittcannon.com/media/pdf/catalogs/e22.23.pdf

These are arrays of 36 rubber switches that can be cut into individual
switches, or selectively cut to make a semi-custom keyboard array if
desired. The really good news is that they come in round, allowing
simple drilling of an enclosure to accommodate a switch.

At Arrow they list for just under $10/36 which comes to about
25c/switch. Right on BOM budget. Sweet. But: There is scant information
about these, no app notes, no recommended drill patterns, thicknesses,
etc. IOW, nada.

The rep promised me a file with recommended land patterns. My question:
Has anyone designed with stuff like this? Share experiences? Are there
other large manufacturers?

Regards, Joerg

Do you need rubber? We use pcb mount mechanical pushbuttons, Panasonic
and Omron, in the 15-19 cent range in fairly small quantities. They
have a nice snappy feel.

http://www.highlandtechnology.com/DSS/P400DS.html

John

 

[Rich Grise]

Do you need rubber? We use pcb mount mechanical pushbuttons, Panasonic
and Omron, in the 15-19 cent range in fairly small quantities. They
have a nice snappy feel.

http://www.highlandtechnology.com/DSS/P400DS.html

Nice product blurb, but how about a link to the switches?

Thanks,
Rich

 

[John Larkin]

Nice product blurb, but how about a link to the switches?

Thanks,
Rich

Oh. Yes. That.

Try Panasonic EVQ-PAC04M sort of stuff, and Omron B3F-1052 ishness.

Also see disgusting relay watchdog circuits in a.b.s.e.

John

 

[Joerg]

Hello John,


Nice system that you've built there.

Try Panasonic EVQ-PAC04M sort of stuff, and Omron B3F-1052 ishness.

I had looked at all those kinds. Up and down Digikey, Mouser, Newark,
Arrow and so on. The problem is that they are only about 3.5mm in push
surface diameter. I have to keep the button surface flush with the front
cover, or rather a tad recessed to deal with tolerances. This in order
to prevent accidental turn-on of the unit when someone lays it down on
the face, tosses a newspaper on top or carries it in a messy briefcase.
The messiness factor of an average briefcase can be quite extreme

The Cannon is 9.5mm diameter so an average finger tip can press it into
a hole without breaking a nail. I really need something wide and round.
Now if women would finally give up on those ugly glued-on nails this
design task would be a lot easier.

Regards, Joerg

 

[Rich Grise, but drunk]

Hello John,
Nice system that you've built there.
I had looked at all those kinds. Up and down Digikey, Mouser, Newark,
Arrow and so on. The problem is that they are only about 3.5mm in push
surface diameter. I have to keep the button surface flush with the front
cover, or rather a tad recessed to deal with tolerances. This in order
to prevent accidental turn-on of the unit when someone lays it down on
the face, tosses a newspaper on top or carries it in a messy briefcase.
The messiness factor of an average briefcase can be quite extreme

The Cannon is 9.5mm diameter so an average finger tip can press it into
a hole without breaking a nail. I really need something wide and round.
Now if women would finally give up on those ugly glued-on nails this
design task would be a lot easier.

How about the stuff they use for the front panels of microwave ovens?
They're zero depth, and big enough for a finger or two. ;-)

Oh, but wait - you don't want them to get accidentally pressed when
the customer tosses the unit into their gym bag.

What to do, what to do....

How big is the front panel? How about a .032" Al sheet, with a .375"
(or so) hole over each "button"? And spec the domes on the topsheet
for "hard-press"? ;-) Ya got a trade-off between "easy to press on
purpose" and "hard to press accidentally, no?"

[Hi Rich, that'd be prohibitively expensive, but thanks for the image!
I'll be tracking down that sort of technology right away! Thanks!
-- Joerg]
</fantasy /\;\-\)\ >

Good Luck!
Rich
--
-----BEGIN GEEK CODE BLOCK-----
Version: 3.1
GAT(E P) dpu s: a++ C++@ P+ L++>+ !E W+ N++ o? K? w-- !O !M !V PS+++
PE Y+ PGP- t 5+++)-; X- R- tv+ b+ DI++++>+ D-? G e+$ h+ r-- z+
------END GEEK CODE BLOCK------

 

[Joerg]

Hello Rich,

What to do, what to do....

How big is the front panel? How about a .032" Al sheet, with a .375"
(or so) hole over each "button"? And spec the domes on the topsheet
for "hard-press"? ;-) Ya got a trade-off between "easy to press on
purpose" and "hard to press accidentally, no?"

[Hi Rich, that'd be prohibitively expensive, but thanks ...

It is too expensive :-(

It's going to be an ABS case, no domes although in the long run we could
do that. Initially it needs to work with a regular flat off-the-shelf
thingie. The rubber buttons might work if we can find an ABS case with a
thick enough front so the button can't be pressed 'under'. That's why I
asked whether anyone has experience with these. However, the fact that
none of the Digikey type businesses carries them does not create a warm
and fuzzy.

Regards, Joerg

 

[Pooh Bear]

Hello Folks,

A while ago I asked about cheap tact switches. I found that none of the
usual ones works well for handheld gear if you don't want to have an
extra cap. Plus they don't come in round to avoid enclosure milling.
After asking the same question in a German forum one of the guys there
(Gunther Mannigel) suggested these:

http://www.ittcannon.com/media/pdf/catalogs/e22.23.pdf

These are arrays of 36 rubber switches that can be cut into individual
switches, or selectively cut to make a semi-custom keyboard array if
desired. The really good news is that they come in round, allowing
simple drilling of an enclosure to accommodate a switch.

At Arrow they list for just under $10/36 which comes to about
25c/switch. Right on BOM budget. Sweet. But: There is scant information
about these, no app notes, no recommended drill patterns, thicknesses,
etc. IOW, nada.

The rep promised me a file with recommended land patterns. My question:
Has anyone designed with stuff like this? Share experiences? Are there
other large manufacturers?

I've had a little experience.

You can make up your own pattern to be honest.

Try googling 'elastomeric switch' and 'membrane switch' for more suppliers.

Graham

 

[Joerg]

Hello Graham,

I've had a little experience.

With the ITT Cannon switches or similar ones?

You can make up your own pattern to be honest.

This is the first series where I saw that being done by just cutting
away switches. Anything else was full custom mold making and the whoile
nine yeards, high up front NRE costs.

Try googling 'elastomeric switch' and 'membrane switch' for more suppliers.

I had tried that. Membrane switches are usually the flat polyester film
layers, not very suitable for a single push button. Elastomeric yields
other companies but typically smaller custom outfitters. The Cannon is,
so far, the only one that I have seen coming standardized off-the-shelf
from a major manufacturer. I was a bit surprised that Omron or Panasonic
don't make them.

Regards, Joerg

 

[Rich Grise]

Hello Rich,

What to do, what to do....

How big is the front panel? How about a .032" Al sheet, with a .375"
(or so) hole over each "button"? And spec the domes on the topsheet
for "hard-press"? ;-) Ya got a trade-off between "easy to press on
purpose" and "hard to press accidentally, no?"

[Hi Rich, that'd be prohibitively expensive, but thanks ...

It is too expensive :-(

It's going to be an ABS case, no domes although in the long run we could
do that. Initially it needs to work with a regular flat off-the-shelf
thingie. The rubber buttons might work if we can find an ABS case with a
thick enough front so the button can't be pressed 'under'. That's why I
asked whether anyone has experience with these. However, the fact that
none of the Digikey type businesses carries them does not create a warm
and fuzzy.

Well, look at the front panel of your microwave. Or, for that matter,
inside a keyboard:
http://www.neodruid.net/KeyZilla/Keyboard1.html
http://www.neodruid.net/KeyZilla/Keyboard2.html

That'd give you your flat switch array, and then just put whatever
size holes you want in your front panel.

Have Fun!
Rich

 

[Joerg]

Hello Rich,

Well, look at the front panel of your microwave. Or, for that matter,
inside a keyboard:
http://www.neodruid.net/KeyZilla/Keyboard1.html
http://www.neodruid.net/KeyZilla/Keyboard2.html

I know, I just had to take mine apart for cleaning. Washed all the
layers and carefully dried them near the wood stove. Now all the keys
work again.

That'd give you your flat switch array, and then just put whatever
size holes you want in your front panel.

You can't easily get this for a one-button situation. Also, look at the
number of parts: Two silver trace layers, one membrane spacer layer, a
rubber post plus a cap. I'd rather have a one-piece solution instead of
five parts.

Regards, Joerg

 

[Pooh Bear]

Hello Rich,


I know, I just had to take mine apart for cleaning. Washed all the
layers and carefully dried them near the wood stove. Now all the keys
work again.


You can't easily get this for a one-button situation. Also, look at the
number of parts: Two silver trace layers, one membrane spacer layer, a
rubber post plus a cap. I'd rather have a one-piece solution instead of
five parts.

Eh ?

What's all this about layers ?

The switch contact fingers are formed by traces on the pcb and the switch (
the contact pill ) sits above it. That's all.

Try taking a TV remote apart. The traces in the switch area will be carbon
coated ( cheaper than gold ).

Graham

 

[Michael A. Terrell]

Eh ?

What's all this about layers ?

The switch contact fingers are formed by traces on the pcb and the switch (
the contact pill ) sits above it. That's all.

Try taking a TV remote apart. The traces in the switch area will be carbon
coated ( cheaper than gold ).

Graham

And a lot less reliable.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Pooh Bear]

And a lot less reliable.

Stop and think how often a TV remote button gets pressed !

Graham

 

[Joerg]

Hello Graham,

Eh ?

What's all this about layers ?

Well, that's what the Rich's link was describing. It's how most lower
cost PC keyboards work or at least used to work.

The switch contact fingers are formed by traces on the pcb and the switch (
the contact pill ) sits above it. That's all.

Try taking a TV remote apart. The traces in the switch area will be carbon
coated ( cheaper than gold ).

That's exactly how the ITT Cannon rubber switches work. I just wanted to
know whether someone had used them and whether the experience was on the
positive side.

Regards, Joerg

 

[Richard H.]

The rep promised me a file with recommended land patterns. My question:
Has anyone designed with stuff like this? Share experiences? Are there
other large manufacturers?

Not yet, but heading down this path. I've dissected a mass-market
product (a flashing toy ring) that uses a similar but smaller single
switchpad. I can share how they implemented it, FWIW...

For a button 10.5mm square with a 5mm round top and a 4mm carbon contact
pad, they laid out a set of 12/12 tinned (?) finger traces 4.5mm long (2
fingers on one net, 3 on the other).

What I can't speak to is longevity of the traces or the contact pad. So
far, oxidation on the traces isn't an issue.

Richard

 

[Joerg]

Hello Richard,

Not yet, but heading down this path. I've dissected a mass-market
product (a flashing toy ring) that uses a similar but smaller single
switchpad. I can share how they implemented it, FWIW...

For a button 10.5mm square with a 5mm round top and a 4mm carbon contact
pad, they laid out a set of 12/12 tinned (?) finger traces 4.5mm long (2
fingers on one net, 3 on the other).

I have seen the 2/3 comb pattern on a remote. Another used 1/2 comb and
failed quite early on. Yet another had them meandered and this also
failed. But these failures could be related to the carbon content
rubbing off.

Tinned? Yuck. That doesn't seem right. Ideally it should be gold plated
but that probably wasn't in the cards. Tinning can lead to problems with
residue like rubbed off post material, dust, Cheerio crumbs, pretzel
parts and so on lodging in between.

What I can't speak to is longevity of the traces or the contact pad. So
far, oxidation on the traces isn't an issue.

Depends on how long you have that toy ring and where it's usually
stored. I found that even the difference between the garage and inside
the house is very noticeable.

If you know other sources beside ITT Cannon please let us all know. I am
pretty sure we won't be the only ones for too long who need this stuff.

Regards, Joerg

 

[Richard H.]

Tinned? Yuck. That doesn't seem right. Ideally it should be gold plated
but that probably wasn't in the cards. Tinning can lead to problems with
residue like rubbed off post material, dust, Cheerio crumbs, pretzel
parts and so on lodging in between.

Yep. This is new turf, so I haven't explored alternatives to gold
plating yet. At the moment, I'm just looking to get a prototype working
with similar parts (e.g., packaged IC instead of die), expecting that
it'll be re-designed by those more knowledgable in commodity products
before it goes to production, if ever. I doubt gold will make the BOM
in the final product due to cost.

Depends on how long you have that toy ring and where it's usually
stored. I found that even the difference between the garage and inside
the house is very noticeable.

Actually, looking closer, it looks like the whole PCB is plated with a
silvery material under the mask; there's no HASL. Whatever it is, it's
very cheap, as you'd expect of a toy - every part of it has clearly been
optimized for cost (down to the commodity mini-LEDs with u-bent leads so
they could use a single-sided PCB).

If you know other sources beside ITT Cannon please let us all know. I am
pretty sure we won't be the only ones for too long who need this stuff.

Hadn't gotten that far yet. Frankly, I was planning to scavenge the
part for the protos and let the re-design guys worry about the source.
The ITT ones are bigger than I need, but may be a workable option too.
I'll let you know if I come across any others.

Cheers,
Richard

 

[Joerg]

Hello Richard,

Yep. This is new turf, so I haven't explored alternatives to gold
plating yet. At the moment, I'm just looking to get a prototype working
with similar parts (e.g., packaged IC instead of die), expecting that
it'll be re-designed by those more knowledgable in commodity products
before it goes to production, if ever. I doubt gold will make the BOM
in the final product due to cost.

Gold or nickel are pretty standard these days but not in very low cost
gear because it is an extra production step. Probably the PCB in your
toy model isn't even FR4 but phenolic. Believe it or not, even large TV
sets often have a phenolic main board to squish the last 10c in cost out
of them.

I'll let you know if I come across any others.

That would be nice.

Regards, Joerg