On Thu, 20 Jul 2017 09:57:42 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
>On Wed, 19 Jul 2017 09:04:37 -0700, John Larkin
><jjlarkin@highlandtechnology.com> wrote:
>
>>Our silicone thing will have little cylindrical posty things that drop
>>into holes on the PCB, for alignment. Then the alignment is dominated
>>by how the user pushes the button, dead center or off-center.
>>
>>https://www.dropbox.com/s/jxcfj8jyy9jt1xs/2p5detail.jpg?raw=1
>
>That should work. Where things go awry is when the keypad sandwich is
>assembled. If over-tightened, the silicone will compress and the flat
>areas of the keypad will migrate outwards. For the small keypad that
>you are using, it's probably not going to be a problem. However,
>better to be safe and put some extra alignment pins near the outside
>edge of the keypad.
Compression is controlled by PEMs between the front pabel and the PCB.
The silicone thing has features that make it somewhat compressible.
>
>>>Incidentally, most of my experience is in marine radio, where such
>>>things are a very real problem.
>
>>The keys will be backlit, and there will be a hole in the PCB, in the
>>middle of the contact pattern (see my pic) that will let the light
>>through and ventilate the backside of the key.
>
>Ugh. You're going to have all kinds of shadows from the center pylon
>along with variations in brightness caused by different wall
>thickness. I suggest dark buttons and clear (laser gouged) lettering
>instead.
I think that will be OK. The silicone will be milky-white and should
diffuse the light pretty well. There is no center pylon; the back side
of the key will be flat. We're getting a couple of prototypes to
evaluate, so we can iterate.
>
>>Some of the keys are not backlit, so maybe I should add vent holes to
>>those. The instrument will dissipate from roughly 15 to maybe 30
>>watts, so it will be nice and warm inside.
>
>I don't think the extra vent holes will be necessary. The heat from
>the instrument will prevent condensation.
>
>However, you still may have a moisture problem if someone decides to
>clean the front of the instrument. I had this problem with marine
>radios that were sold to the USCG (US Coast Guard). The average
>fisherman cleans his radios exactly once, just before he sells the
>vessel. However, the USCG is very much into keeping things clean. For
>example, on the 44ft MLB (motor life boat):
><https://www.google.com/search?q=uscg+44+ft+mlb&tbm=isch>
>the deck and everything on it would be hosed down with fresh water. If
>the equipment was dirty, someone would clean it with some kind of
>household ammonia and alcohol cleaner. Both of these were problems.
>The wash down would drive water past any marginal seals and into the
>radio. The magic cleaner would dissolve off screening and keypad
>labels.
>
>I wouldn't expect your customers to hose down your instrument.
>However, they might decide that clean the front panel. Done
>vigorously and too often, it might do some damage. I while back, I
>used some 409 cleaner to wipe the front of some instrument and had all
>the white paint rub off. Painted lettering is going to be a problem
>because the paint needs to be flexible to survive on the flexible
>silicone rubber surface. If it's too hard, it will flake off. If too
>soft, it will dissolve off with cleaners. I suggest you look into
>laser scribing the silicone keypad:
><https://www.youtube.com/watch?v=OXwWGXazuBM>
><https://www.youtube.com/watch?v=ZDWaKUX160Q>
I could include cleaning guidelines in the manual.
The non-illuminated keys will look better with black lettering.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Reply by Jeff Liebermann●July 20, 20172017-07-20
On Wed, 19 Jul 2017 09:04:37 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:
>Our silicone thing will have little cylindrical posty things that drop
>into holes on the PCB, for alignment. Then the alignment is dominated
>by how the user pushes the button, dead center or off-center.
>
>https://www.dropbox.com/s/jxcfj8jyy9jt1xs/2p5detail.jpg?raw=1
That should work. Where things go awry is when the keypad sandwich is
assembled. If over-tightened, the silicone will compress and the flat
areas of the keypad will migrate outwards. For the small keypad that
you are using, it's probably not going to be a problem. However,
better to be safe and put some extra alignment pins near the outside
edge of the keypad.
>>Incidentally, most of my experience is in marine radio, where such
>>things are a very real problem.
>The keys will be backlit, and there will be a hole in the PCB, in the
>middle of the contact pattern (see my pic) that will let the light
>through and ventilate the backside of the key.
Ugh. You're going to have all kinds of shadows from the center pylon
along with variations in brightness caused by different wall
thickness. I suggest dark buttons and clear (laser gouged) lettering
instead.
>Some of the keys are not backlit, so maybe I should add vent holes to
>those. The instrument will dissipate from roughly 15 to maybe 30
>watts, so it will be nice and warm inside.
I don't think the extra vent holes will be necessary. The heat from
the instrument will prevent condensation.
However, you still may have a moisture problem if someone decides to
clean the front of the instrument. I had this problem with marine
radios that were sold to the USCG (US Coast Guard). The average
fisherman cleans his radios exactly once, just before he sells the
vessel. However, the USCG is very much into keeping things clean. For
example, on the 44ft MLB (motor life boat):
<https://www.google.com/search?q=uscg+44+ft+mlb&tbm=isch>
the deck and everything on it would be hosed down with fresh water. If
the equipment was dirty, someone would clean it with some kind of
household ammonia and alcohol cleaner. Both of these were problems.
The wash down would drive water past any marginal seals and into the
radio. The magic cleaner would dissolve off screening and keypad
labels.
I wouldn't expect your customers to hose down your instrument.
However, they might decide that clean the front panel. Done
vigorously and too often, it might do some damage. I while back, I
used some 409 cleaner to wipe the front of some instrument and had all
the white paint rub off. Painted lettering is going to be a problem
because the paint needs to be flexible to survive on the flexible
silicone rubber surface. If it's too hard, it will flake off. If too
soft, it will dissolve off with cleaners. I suggest you look into
laser scribing the silicone keypad:
<https://www.youtube.com/watch?v=OXwWGXazuBM>
<https://www.youtube.com/watch?v=ZDWaKUX160Q>
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Reply by John Larkin●July 19, 20172017-07-19
On Wed, 19 Jul 2017 12:44:36 -0700 (PDT), Klaus Kragelund
<klauskvik@hotmail.com> wrote:
>Just out of curiosity why would you use low quality keypad for a high quality instrument?
>
>Cheers
>
>Klaus
We're not. The pic was just an example we have around. Melrose is
making us a custom silicone button thing. Tek, Keysight, Fluke use
similar buttons.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Reply by Klaus Kragelund●July 19, 20172017-07-19
Just out of curiosity why would you use low quality keypad for a high quality instrument?
Cheers
Klaus
Reply by John Larkin●July 19, 20172017-07-19
On Wed, 19 Jul 2017 08:39:58 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
>On Wed, 19 Jul 2017 10:29:23 -0400, "Carl Ijames"
><carl.ijamesDDD@EEEverizon.net> wrote:
>
>>Wonder why they don't simply mold ridges into the rubber sheet around each
>>button, on both sides?
>
>The ridge is present, but on the front panel or bezel. That's because
>there are far more silicone keypads found on cordless phones, TV
>remotes, radios, toys, test equipment, etc, than on test equipment.
>All of these devices tend to have a custom molded front panel, while
>test equipment tends to get a flat aluminum plate. Putting the seal
>(ridge) on the keypad would work, but then they couldn't use the same
>silicone keypad on both plastic molded and flat aluminum front panels.
>
>>That would make sort of an oring that would keep
>>stuff from between panel and keypad on the outside, and keep moisture off
>>the button contact on the inside. (Just like GM and others make intake
>>manifold gaskets these days :-).)
>
>Actually, sealing the entire keypad is also a bad idea unless you can
>figure out a way to do a hermitic seal. Water will condense out of
>"thin air" inside the keypad anyway. If one can't have a totally
>sealed and pressurized keypad, the next best thing is one that drips
>accumulated water out the bottom. That's why I like to add solder
>mask on the back PCB under the entire keypad, so that any accumulated
>water, will not short the traces. However, the current fashion is to
>punch small holes in the silicone keypad that mate with pins in the
>front panel or back PCB to align the keypad so that the carbon buttons
>hit dead center on the contacts. These holes will cause problems if
>one wants to seal the keypad.
Our silicone thing will have little cylindrical posty things that drop
into holes on the PCB, for alignment. Then the alignment is dominated
by how the user pushes the button, dead center or off-center.
https://www.dropbox.com/s/jxcfj8jyy9jt1xs/2p5detail.jpg?raw=1
Incidentally, Autocad has a decent online STEP file viewer
https://a360.autodesk.com/viewer/
but the measurement tool makes no sense to me.
>
>I once suspected that simply pushing the buttons will produced enough
>positive pressure to pump out some of this accumulated water, but
>never bothered to test or calculate it.
>
>Incidentally, most of my experience is in marine radio, where such
>things are a very real problem.
The keys will be backlit, and there will be a hole in the PCB, in the
middle of the contact pattern (see my pic) that will let the light
through and ventilate the backside of the key.
Some of the keys are not backlit, so maybe I should add vent holes to
those. The instrument will dissipate from roughly 15 to maybe 30
watts, so it will be nice and warm inside.
--
John Larkin Highland Technology, Inc
lunatic fringe electronics
>Wonder why they don't simply mold ridges into the rubber sheet around each
>button, on both sides?
The ridge is present, but on the front panel or bezel. That's because
there are far more silicone keypads found on cordless phones, TV
remotes, radios, toys, test equipment, etc, than on test equipment.
All of these devices tend to have a custom molded front panel, while
test equipment tends to get a flat aluminum plate. Putting the seal
(ridge) on the keypad would work, but then they couldn't use the same
silicone keypad on both plastic molded and flat aluminum front panels.
>That would make sort of an oring that would keep
>stuff from between panel and keypad on the outside, and keep moisture off
>the button contact on the inside. (Just like GM and others make intake
>manifold gaskets these days :-).)
Actually, sealing the entire keypad is also a bad idea unless you can
figure out a way to do a hermitic seal. Water will condense out of
"thin air" inside the keypad anyway. If one can't have a totally
sealed and pressurized keypad, the next best thing is one that drips
accumulated water out the bottom. That's why I like to add solder
mask on the back PCB under the entire keypad, so that any accumulated
water, will not short the traces. However, the current fashion is to
punch small holes in the silicone keypad that mate with pins in the
front panel or back PCB to align the keypad so that the carbon buttons
hit dead center on the contacts. These holes will cause problems if
one wants to seal the keypad.
I once suspected that simply pushing the buttons will produced enough
positive pressure to pump out some of this accumulated water, but
never bothered to test or calculate it.
Incidentally, most of my experience is in marine radio, where such
things are a very real problem.
>Would work best if the raised ring didn't
>cross any traces on the pcb, which would require using vias to connect each
>switch, but it would probably seal ok even without that.
"John Larkin" wrote in message
news:r3qumctepgcqs1idd272qc7aho1gpd2dv9@4ax.com...
On Tue, 18 Jul 2017 22:48:10 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
>Got any TV remotes, cordless phones, or other devices that use
>rubberish keypads? If you take them apart and look at how they're
>built, you'll notice that the back of the front panel has ridges
>around each button. These ridges prevent water, dust, or debris from
>getting between the front panel and the silicon keypad. The ridge is
>under compression from the keypad PCB mounting hardware to the front
>panel, thus providing a very good seal. However, doing the same thing
>with an aluminum front panel is not going to happen. There's just no
>way to coin a ridge into the front panel. It might be possible to
>glue a frame with similar ridges to the front panel, but that costs
>money and is labor intensive. I don't know if you're going to need
>any environmental protection, but I thought it might help to explain
>why and how it's done.
The one in that pic was just something we pulled off a dead
instrument. Ours will be bigger (1/2 rack instrument) and better. The
silicone will be squeezed between the aluminum panel and the PCB, so
should seal pretty well. We always specify our temperature range as
something like "0-50C non-condensing"
=========================================================
Wonder why they don't simply mold ridges into the rubber sheet around each
button, on both sides? That would make sort of an oring that would keep
stuff from between panel and keypad on the outside, and keep moisture off
the button contact on the inside. (Just like GM and others make intake
manifold gaskets these days :-).) Would work best if the raised ring didn't
cross any traces on the pcb, which would require using vias to connect each
switch, but it would probably seal ok even without that.
--
Regards,
Carl Ijames
>On Tue, 18 Jul 2017 14:05:02 -0700, the renowned John Larkin
><jjlarkin@highland_snip_technology.com> wrote:
>
>>
>>
>>We're doing a custom silicone pushbutton thing, sort of like this one:
>>
>>https://www.dropbox.com/s/8hihd888w7rtxmx/Fingers_2.JPG?raw=1
>>
>>https://www.dropbox.com/s/ruo7zujvx7mxerz/Fingers_3.JPG?raw=1
>>
>>The pcb below the keypad will look something like
>>
>>https://www.dropbox.com/s/qyu2nrkhom78wkl/Fingers_1.jpg?raw=1
>>
>>where the center hole lets light through to back-light the key, and
>>the two finger patterns are where the carbon buttons land when the key
>>is pressed. This will be ENIG, gold flash over nickel over PCB copper.
>>
>>The left and right finger patterns will be electrically in parallel.
>>It's possible for one carbon button to contact, or both, depending on
>>how the button is pushed.
>>
>>Googling, I find zillions of different and bizarre PCB patterns for
>>the buttons to land on. Crazy shapes.
>>
>>Has anyone done this? Any opinions on the optimum PCB pattern?
>
>Do the silicon keyboard design guides (there are several out there)
>provide any guidance to the PCB patterns?
>
>--sp
Yes, a wide array of sensible and bizarre patterns.
--
John Larkin Highland Technology, Inc
lunatic fringe electronics
Reply by John Larkin●July 19, 20172017-07-19
On Tue, 18 Jul 2017 22:48:10 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
>On Tue, 18 Jul 2017 17:35:12 -0700, John Larkin
><jjlarkin@highland_snip_technology.com> wrote:
>
>>I don't think I'll worry about water. My pullup resistors will be 10K!
>
>What, me worry? Here's a simple test to try. Put the keyboard and
>associated electronics into your environmental chamber or fridge and
>drop the temperature to well below the dew point. Bring the device
>out of the chamber or fridge into the warm room. Water will condense
>on everything but the real question will be will it condense inside
>the keypad and simulate a keypress.
>
>One of my early jobs was for a company that made communications
>accessories. In this case, it was a touch tone encoder for 2way
>radios in skool buses. Everything worked just fine until they were
>installed in the buses. The buses would sit outside in the cold
>night. At the crack-o-dawn, the engines would be started and the
>interiors warmed up in preparation for picking up the students. Water
>would condense inside the keypad, which would cause the transmitters
>to key up. Having about 50 transmitters stuck on the air just as the
>buses were leaving the yard was not a good thing.
>
>>The silicone pad will be difficult to remove, sandwiched between a PCB
>>and an aluminum panel, so I hope it won't need cleaning. I'll ask the
>>vendor about that oozing gunk possibility.
>
>Yep, that's the way most of them are built, with the silicon keyboard
>sandwiched between an expensive decorative front panel, and an
>expensive PCB full of electronics.
That's OK, we'll charge a lot too.
>
>Got any TV remotes, cordless phones, or other devices that use
>rubberish keypads? If you take them apart and look at how they're
>built, you'll notice that the back of the front panel has ridges
>around each button. These ridges prevent water, dust, or debris from
>getting between the front panel and the silicon keypad. The ridge is
>under compression from the keypad PCB mounting hardware to the front
>panel, thus providing a very good seal. However, doing the same thing
>with an aluminum front panel is not going to happen. There's just no
>way to coin a ridge into the front panel. It might be possible to
>glue a frame with similar ridges to the front panel, but that costs
>money and is labor intensive. I don't know if you're going to need
>any environmental protection, but I thought it might help to explain
>why and how it's done.
>
>>I'll ask the
>>vendor about that oozing gunk possibility.
>
>It's quite real:
><https://groups.google.com/forum/#!topic/sci.electronics.repair/wU2OlitgXpc>
><http://www.michaelshell.org/gadgetsandfixes/keypadsiliconeoil.html>
><http://p1repair.com/blog/2013/05/28/rubber-keypad-problems-liquid-oil-moisture-found-inside-the-buttons-what-is-it-where-does-it-come-from/>
>
>Two other potential problems. Women and some men with very sharp
>fingernails will cut into the soft silicone with their fingernails.
>That's another reason for an easily replaceable keypad. In the
>photos, your buttons look small enough that I would not expect a
>problem but you might want to make sure that the buttons stick out
>from the front panel far enough that the typical fingernail doesn't
>scratch the front panel. I also noticed that the silk screened or
>painted lettering on the buttons uses rather narrow lines. The rubber
>stretches and moves sufficiently that the lettering might flake off.
>Try wider line widths for better adhesion.
The one in that pic was just something we pulled off a dead
instrument. Ours will be bigger (1/2 rack instrument) and better. The
silicone will be squeezed between the aluminum panel and the PCB, so
should seal pretty well. We always specify our temperature range as
something like "0-50C non-condensing"
--
John Larkin Highland Technology, Inc
lunatic fringe electronics
Reply by ●July 19, 20172017-07-19
> >
> >Has anyone done this? Any opinions on the optimum PCB pattern?
>
seems the critical issue for long term reliability is
what and how the conductive stuff is attached to the buttons.
m