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'[EE] need suggestions for low-force double pole sw'
2006\02\22@110943 by peiserma

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face
As the subject indicates, I am looking for a low-force switch. The
switch serves as an interlock for a bed-of-nails tester: The tester has
a plastic cover with a protruding pin. The pin actuates the switch when
the cover is closed. It is important that the switch be a double-pole
type so it breaks both sides of the line. Picture can be provided if it
helps.

The problem I'm running into is that the only double-pole switches I've
found are 15+ Amps and require a significant amount of force to actuate.
The plastic cover's weight is not enough to actuate the current switch
that was selected. In this case, a Cherry E20-series with a lever,
specified actuating force is 312 gram. (Of course, force should be
measured in Newton, not gram, but I didn't write the datasheet) I
measured the effective weight of the cover at 120 grams (the cover is on
a hinge. 'effective' in this case means the weight seen by the switch).
So the switch needs to be activated with less than 1.18N

The tester will be used on both AC and DC powered boards. So i need a
switch that is rated for 3A 250V, and one that can handle around 8A at
15V. Would be a bonus if the same switch could be used. Doesn't matter
if it's a plunger or lever style. Must be double-pole (doesn't have to
be double-throw. a NO-type would do). Must be activated by less than 120
grams/1.18N.

Any suggestions or pointers would be appreciated. One possibility is
taking two single-pole switches and linking them mechanically, but that
seems less reliable/more troublesome than a single switch.

Phil Eisermann
Electronics Engineer
Ridge Tool Co
(440)329-4680

2006\02\22@112657 by Alan B. Pearce

face picon face
>The tester will be used on both AC and DC powered boards.
>So i need a switch that is rated for 3A 250V, and one that
>can handle around 8A at 15V. Would be a bonus if the same
>switch could be used. Doesn't matter if it's a plunger or
>lever style. Must be double-pole (doesn't have to be
>double-throw. a NO-type would do). Must be activated by
>less than 120 grams/1.18N.

Why not use a suitable relay operated by a microswitch? It sounds like
whatever supply drives the UUT should have enough spare power for a relay
coil.

2006\02\22@113449 by Wouter van Ooijen

face picon face
> Any suggestions or pointers would be appreciated. One possibility is
> taking two single-pole switches and linking them
> mechanically, but that
> seems less reliable/more troublesome than a single switch.

use a low-force SPST switch and a relais?

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2006\02\22@114051 by David VanHorn

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>
>
> The tester will be used on both AC and DC powered boards. So i need a
> switch that is rated for 3A 250V, and one that can handle around 8A at
> 15V. Would be a bonus if the same switch could be used. Doesn't matter
> if it's a plunger or lever style. Must be double-pole (doesn't have to
> be double-throw. a NO-type would do). Must be activated by less than 120
> grams/1.18N.


High current switches typically require larger contact force, and therefore
more actuation force.  I think you need to export that function to a relay.
Also, do you really want to bring line current up to that point?

2006\02\22@114052 by Geo

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On 22 Feb 2006, at 11:08, spam_OUTpeisermaTakeThisOuTspamridgid.com wrote:

> The problem I'm running into is that the only double-pole switches I've
> found are 15+ Amps and require a significant amount of force to actuate.
Sounds like a use for a relay.
You could then use magnet on the lid and reed relay to operate the main contactor.

George Smith

2006\02\22@121337 by Bob Axtell

face picon face
peiserma@ridgid.com wrote:

{Quote hidden}

Mount a piece of metal than will bring a magnet near a reed switch. The
current thru the
reed will be very small, but is enough to actuate a sturdy DPST relay.

--Bob

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Note: To protect our network,
attachments must be sent to
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2006\02\22@134718 by peiserma

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piclist-bounces@mit.edu wrote:
>> The tester will be used on both AC and DC powered boards. So i need a
>> switch that is rated for 3A 250V, and one that can handle around 8A
>> at 15V. Would be a bonus if the same switch could be used. Doesn't
>> matter if it's a plunger or lever style. Must be double-pole
>> (doesn't have to be double-throw. a NO-type would do). Must be
>> activated by less than 120 grams/1.18N.
>
>
> High current switches typically require larger contact force,
> and therefore more actuation force.  I think you need to
> export that function to a relay.

it sounds like that's the right fix in this case. I like the
reed-relay (or a prox. sensor) triggering a larger relay.

> Also, do you really want to bring line current up to that point?

well, no. But the wiring is all internal, away from human hands. There's
a hole in the case for the pin. The switch is inside the case, also.

Thanks for the suggestions. Will have to check with the designers how
much room is left.

2006\02\22@145318 by Paul Hutchinson

picon face
>-----Original Message-----
>From: piclist-bouncesspamKILLspammit.edu On Behalf Of .....peisermaKILLspamspam.....ridgid.com
>Sent: Wednesday, February 22, 2006 11:09 AM
>
<snip>
>
>The problem I'm running into is that the only double-pole switches I've
>found are 15+ Amps and require a significant amount of force to actuate.
>The plastic cover's weight is not enough to actuate the current switch
>that was selected. In this case, a Cherry E20-series with a lever,
>specified actuating force is 312 gram. (Of course, force should be
>measured in Newton, not gram, but I didn't write the datasheet) I
>measured the effective weight of the cover at 120 grams (the cover is on
>a hinge. 'effective' in this case means the weight seen by the switch).
>So the switch needs to be activated with less than 1.18N
<snip>

How about adding a 250g lead weight to the cover at the pin that should
operate the 312g switch reliably. Another thought is to use a spring loaded
hinge on the cover to give the cover more force.

Paul

2006\02\22@150649 by Geo

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face
On 22 Feb 2006, at 14:53, Paul Hutchinson wrote:

> How about adding a 250g lead weight to the cover at the pin that should
> operate the 312g switch reliably. Another thought is to use a spring loaded
> hinge on the cover to give the cover more force.

I thought for a while there was not going to be an alternative
and for once no arguments - nice one, Paul...



George

2006\02\22@161120 by Peter

picon face

reed switch + magnet + relay

leaf switch + relay

Peter

2006\02\22@163852 by peiserma
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face
piclist-bounces@mit.edu wrote:
>> -----Original Message-----
>> From: EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu On Behalf Of peisermaspamspam_OUTridgid.com
>> Sent: Wednesday, February 22, 2006 11:09 AM
>>
> <snip>
>>
>> The problem I'm running into is that the only double-pole switches
>> I've found are 15+ Amps and require a significant amount of force to
>> actuate.
>
> How about adding a 250g lead weight to the cover at the pin
> that should operate the 312g switch reliably.

yeah, that was a thought, but was thought to be lacking aesthetics.

> Another thought is to use a spring loaded hinge on the cover to give
> the cover more force.

now that sounds potentially promising. Nice idea!

2006\02\22@224133 by Bill & Pookie

picon face
Combining the micro switch and the relay, have the "protruding pin" push
down the movable contact on the relay instead of the coil pulling it down.

Pookie

{Original Message removed}

2006\02\22@225307 by Bill & Pookie

picon face
protruding pin  -->  relay = switch

Pookie

----- Original Message -----
From: "Peter" <@spam@plpKILLspamspamactcom.co.il>
To: "Microcontroller discussion list - Public." <KILLspampiclistKILLspamspammit.edu>
Sent: Wednesday, February 22, 2006 1:11 PM
Subject: Re: [EE] need suggestions for low-force double pole switch


>
> reed switch + magnet + relay
>
> leaf switch + relay
>
> Peter
> --

2006\02\23@091812 by Mark Scoville

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> Of Bill & Pookie
> Sent: Wednesday, February 22, 2006 10:41 PM
>
> Combining the micro switch and the relay, have the "protruding pin" push
> down the movable contact on the relay instead of the coil pulling it down.
>
> Pookie

There are relays made with "push-to-test" buttons built-in that mechanicaly
move the relay "wiper" contacts. We use them here. An example is a SongChuan
703XBM - DPDT unit rated for 10A @ 120Vac. I can't seem to locate a good
picture. The relay is about 1" x 1" X 2" (We call them ice cube relays since
they are in clear plastic cases and look a little like ice-cubes). The test
button is about 1/8" dia and sticks out from the case about 1/8". I don't
know the actuation force needed on the test button though. I suppose I could
measure it if you're interested. I'm sure other relay people make similar
units.

Maybe as Pookie suggest, you could have the pin on your tester simply push
the test button on the relay - simple solution.

-- Mark

P.S. Hey peisermann - I see you are in the 440 area code - you must be
nearby. I work in Parma, OH.



2006\02\23@150207 by Peter

picon face

On Wed, 22 Feb 2006, Bill & Pookie wrote:

> protruding pin  -->  relay = switch

But not enough force and not fast-closing (he switches mains). It would
work with a bistable switch with the spring tuned so it takes much less
force to 'make' than to 'break'. Think mousetrap.

Peter

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