DPST momentary tactile switches - do they even exist?

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Hi - I'm looking for a very small and low profile DPST momentary
tactile switch. Problem is - I can't find *any*. Naturally a DPDT would
be ok as well. Best I've been able to find is some DPDTs that stick up
maybe 15mm. I'm looking for something of the ~8x8x5mm variety. Does
such a beast exist? Thanks,

-Noone


Re: DPST momentary tactile switches - do they even exist?


On 26 Dec 2005 15:40:40 -0800, the renowned "M. Noone"

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Tact switches are 'naturally' SPST-NO. Can't you stick some circuitry
or even a small relay on there to get the functionality you need?


Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
snipped-for-privacy@interlog.com             Info for manufacturers: http://www.trexon.com
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Re: DPST momentary tactile switches - do they even exist?


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You reminded me that I do want them to be NO, which I forgot to mention
in my OP. I'm sure it would be possible to add in some additional
circuitry to make a SPST work - but it would be complicated. The
problem is that this button will be acting as a reset. It will be
grounded and then each pole will be connected to the active low disable
input of two power regulators. (low = off, high/high impedance = on).
Thus when the button is pressed all regulated power on the board is
gone, so driving a relay or other supporting logic gets tricky. I'd
have to use the unregulated power.

It seems the standard package for a low profile tactile switch has 4
contacts - it just seems a natural to me that there'd be some DPSTs...
Thanks,

-Noone


Re: DPST momentary tactile switches - do they even exist?


On 26 Dec 2005 15:58:19 -0800, the renowned "M. Noone"

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Tricky is the way to go, IMO. Can you isolate the /disables with a
dual Schottky diode or something?

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They mostly do that so that you can make an X-Y matrix easily on a
cheap-as-dirt single-layer board. For mechanical support + built-in
jumpers.



Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
snipped-for-privacy@interlog.com             Info for manufacturers: http://www.trexon.com
We've slightly trimmed the long signature. Click to see the full one.
Re: DPST momentary tactile switches - do they even exist?



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See mouser electronics page 1123 SKRNPCE010

MFGR  page
http://www3.alps.co.jp/WebObjects/catalog.woa/PDF/E/Switch/Tact/SKRN/SKRN.PDF
--
JosephKK


Re: DPST momentary tactile switches - do they even exist?


Hello M.,

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Can you use two BSS123? Sources to GND, drains to the respective
regulator control pins, gates tied together, resistor from gate node to
ground and then the button sends unregulated VCC onto the gate node for
the shut-off function. If the unregulated VCC is higher than the gate
breakdown you'd need one more resistor to create a voltage divider. The
BSS123 comes in SOT23 which should be small enough.


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If Digikey doesn't have any they might really be unobtanium.

Regards, Joerg

http://www.analogconsultants.com

Re: DPST momentary tactile switches - do they even exist?



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If that were really the case, and it were I who needed the DPST function,
I might mount two side-by-side and epoxy a little piece of plastic, like
the way they do ganged circuit breakers.

If I were really desperate, of course. :-)

Good Luck!
Rich


Re: DPST momentary tactile switches - do they even exist?


Hello Rich,

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Thought about that as well. But it will be a bear in production because
you'd have to glue the bar on top or engage in some elaborate molding to
hold it in place. Glueing will cause grief such as the glue running into
the switch and so on.

Then there is the issue of veered and incomplete button pressing. That
can cause one regulator to stop while the other keeps cranking.

Regards, Joerg

http://www.analogconsultants.com

Re: DPST momentary tactile switches - do they even exist?



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I presume your mounting space is too thin for an ordinary microswitch:
http://www.mouser.com/catalog/624/1116.pdf
but I've seen inside the guts of them, and the mech could be done in
probably less than 1/4" (6-7 mm) depth.

And I think if you shop around, you could find a double-pole version.

Good Luck!
Rich


Re: DPST momentary tactile switches - do they even exist?


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Normally you'd design around the fact that tac switches are single pole
NO. But if you must have a 2 pole one, its not difficult. The black
conductive material is a thin layer on the underside of the switch.
Simply cut out a strip across the middle. You now have 2 conductive
pads. Design the PCB pads accordingly, and you have a 2 pole switch.

The one issue you need to watch for is that it might in some cases
enable a user to squish the rubber over to short the 2 poles together.
Attention to detail.

NT


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