Cheap air pressure switch?
 

I want to sense pressure in a line that feeds part clamps and turn on a
green light and/or have a red light go out so the operator will try to
remember to clamp the parts. (don't laugh) I could use a compressor switch
for about $30 and a search finds sensors for about $80. Can I use an
automotive oil pressure idiot light switch or something like those? They
are only $5-$10. Any other ideas?

Cheap air pressure switch?
 

Idiot light OPS are good to 100psi or so; usually NC, trigger at 3psi.
VW ones also can be NO to 1.8 bar.
JR
Dweller in the cellar

On Tue, 16 Sep 2008 20:29:35 -0400, "Tom Gardner"
wrote:

I want to sense pressure in a line that feeds part clamps and turn on a
green light and/or have a red light go out so the operator will try to
remember to clamp the parts. (don't laugh) I could use a compressor switch
for about $30 and a search finds sensors for about $80. Can I use an
automotive oil pressure idiot light switch or something like those? They
are only $5-$10. Any other ideas?

--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth
If you're not the lead dog, the view never changes
Doubt yourself, and the real world will eat you alive
The world doesn't revolve around you, it revolves around me
No skeletons in the closet; just decomposing corpses
--------------------------------------------------------------
Dependence is Vulnerability:
--------------------------------------------------------------
"Open the Pod Bay Doors please, Hal"
"I'm sorry, Dave, I'm afraid I can't do that.."

Cheap air pressure switch?
 

Tom Gardner wrote:
I want to sense pressure in a line that feeds part clamps and turn on a
green light and/or have a red light go out so the operator will try to
remember to clamp the parts.
(...)

Three bucks for a 100 PSI brake light switch. Only 911 are left.
http://www.surpluscenter.com/item.as...-2400&catname=

--Winston

Cheap air pressure switch?
 

On Tue, 16 Sep 2008 20:29:35 -0400, "Tom Gardner"
wrote:

I want to sense pressure in a line that feeds part clamps and turn on a
green light and/or have a red light go out so the operator will try to
remember to clamp the parts. (don't laugh) I could use a compressor switch
for about $30 and a search finds sensors for about $80. Can I use an
automotive oil pressure idiot light switch or something like those? They
are only $5-$10. Any other ideas?

Air cylinder, stiff return spring, flag on the cylinder's rod end that
pops up in the operator's face when the air pressure overcomes the
spring.

--
Ned Simmons

Cheap air pressure switch?
 

Tom Gardner wrote:
I want to sense pressure in a line that feeds part clamps and turn on a
green light and/or have a red light go out so the operator will try to
remember to clamp the parts. (don't laugh) I could use a compressor switch
for about $30 and a search finds sensors for about $80. Can I use an
automotive oil pressure idiot light switch or something like those? They
are only $5-$10. Any other ideas?



What pressure. There are A/C system switches as well as oil pressure
switches and even brake light switches that operate using brake
pressure. The OP idiot light switches usually turn OFF (NC contacts) at
about 5-8 PSI. The A/C switches depend on which end of the system they
are on. The high pressure switches usually turn on about 120-140 PSI
(and there are adjustable ones)
The brake pressure light switches turn on around 100-150 PSI. (Ford,
Chrysler)

--
Steve W.

Cheap air pressure switch?
 

"Winston" wrote in message
news:N_Zzk.367$8v5.105@trnddc01...
Tom Gardner wrote:
I want to sense pressure in a line that feeds part clamps and turn on a
green light and/or have a red light go out so the operator will try to
remember to clamp the parts.
(...)

Three bucks for a 100 PSI brake light switch. Only 911 are left.
http://www.surpluscenter.com/item.as...-2400&catname=

--Winston

Perfect! Thanks!

Cheap air pressure switch?
 

Tom Gardner wrote:
I want to sense pressure in a line that feeds part clamps and turn on a
green light and/or have a red light go out so the operator will try to
remember to clamp the parts. (don't laugh) I could use a compressor switch
for about $30 and a search finds sensors for about $80. Can I use an
automotive oil pressure idiot light switch or something like those? They
are only $5-$10. Any other ideas?


I'll bet that would work fine. It might eventually fail after 5 years
or so with the pressure going on/off/on all the time. Buy two.
There likely is a less expensive strain gauge type sensor available that
would last forever since there is no bellows constantly stretching.

Jon

Cheap air pressure switch?
 

Winston wrote:
Tom Gardner wrote:
I want to sense pressure in a line that feeds part clamps and turn on
a green light and/or have a red light go out so the operator will try
to remember to clamp the parts.
(...)

Three bucks for a 100 PSI brake light switch. Only 911 are left.
http://www.surpluscenter.com/item.as...-2400&catname=
Umm, these are good to thousands of PSI, my guess is the trip pressure
may be anywhere from 50 - 250 PSI on each unit. They may not work in a
system with just 100 PSI line pressure.

Jon

Cheap air pressure switch?
 

Jon Elson wrote:
Winston wrote:

Tom Gardner wrote:

I want to sense pressure in a line that feeds part clamps and turn on
a green light and/or have a red light go out so the operator will try
to remember to clamp the parts.

(...)

Three bucks for a 100 PSI brake light switch. Only 911 are left.
http://www.surpluscenter.com/item.as...-2400&catname=


Umm, these are good to thousands of PSI, my guess is the trip pressure
may be anywhere from 50 - 250 PSI on each unit. They may not work in a
system with just 100 PSI line pressure.

Jon

The part is spec'ed at "100 PSI", (+- something).

It looks to be a piston - activated device. What might cause the switch to
work properly yet activate at a pressure significantly different than 100 PSI?

The piston / cylinder could change diameter by more than a few percent. (Unlikely.)

The return spring behind the piston could change pressure.
(Possible with temperature change though we can be pretty sure Tom's shop stays
cooler than the temperature commonly found in the area of a car firewall).

Piston stiction caused by 1000's of wear cycles could cause it to activate at
different pressures from cycle to cycle.
(Possible. The replacement part is not expensive.)

At three bucks one could afford to buy 20 and cherry pick for actuation
pressure.

Tom, you can also try the 'low pressure' version. It's not cheap, though.
http://barrywhitesrrc.com/Merchant2/...gory_Code=PROD

Eighteen smackers, yikes!

--Winston

Cheap air pressure switch?
 

http://www.grainger.com/Grainger/items/2FBR7
AC-refer switch, look around, various pressures.
Greg

Cheap air pressure switch?
 

"Winston" wrote in message
news:_YbAk.275$UB3.130@trnddc07...
Jon Elson wrote:
Winston wrote:

Tom Gardner wrote:

I want to sense pressure in a line that feeds part clamps and turn on a
green light and/or have a red light go out so the operator will try to
remember to clamp the parts.

(...)

Three bucks for a 100 PSI brake light switch. Only 911 are left.
http://www.surpluscenter.com/item.as...-2400&catname=


Umm, these are good to thousands of PSI, my guess is the trip pressure
may be anywhere from 50 - 250 PSI on each unit. They may not work in a
system with just 100 PSI line pressure.

Jon

The part is spec'ed at "100 PSI", (+- something).

It looks to be a piston - activated device. What might cause the switch
to
work properly yet activate at a pressure significantly different than 100
PSI?

The piston / cylinder could change diameter by more than a few percent.
(Unlikely.)

The return spring behind the piston could change pressure.
(Possible with temperature change though we can be pretty sure Tom's shop
stays
cooler than the temperature commonly found in the area of a car
firewall).

Piston stiction caused by 1000's of wear cycles could cause it to activate
at
different pressures from cycle to cycle.
(Possible. The replacement part is not expensive.)

At three bucks one could afford to buy 20 and cherry pick for actuation
pressure.

Tom, you can also try the 'low pressure' version. It's not cheap, though.
http://barrywhitesrrc.com/Merchant2/...gory_Code=PROD

Eighteen smackers, yikes!

--Winston

I'll get a bunch of the $3 guys and test them. Shop air rarely falls below
110, but even at $18 they won't hurt my budget. (which is about $5k over
already)

Cheap air pressure switch?
 

"Greg O" wrote in message
m...
http://www.grainger.com/Grainger/items/2FBR7
AC-refer switch, look around, various pressures.
Greg

Excellent option if the $3 ones are problematic!

Cheap air pressure switch?
 

Tom Gardner wrote:

I'll get a bunch of the $3 guys and test them. Shop air rarely falls below
110, but even at $18 they won't hurt my budget.

Please let us know how it goes.

--Winston

Cheap air pressure switch?
 

On Sep 16, 5:29*pm, "Tom Gardner" wrote:
I want to sense pressure in a line that feeds part clamps and turn on a
green light and/or have a red light go out so the operator will try to
remember to clamp the parts. *(don't laugh) *I could use a compressor switch
for about $30 and a search finds sensors for about $80. *Can I use an
automotive oil pressure idiot light switch or something like those? *They
are only $5-$10. *Any other ideas?

I'm fond of Nason pressure switches. I needed a SPDT oil pressure
switch for my car that operated at 15psi but didn't want to pay an arm
and a leg for one. A standard oil pressure switch operates at 3-5
psi, which for me is way too late. The 15 psi gave me the warning I
needed, and on the engines I've used them on, the light would barely
flicker when the engine was really hot. Got it from my local Carquest
that ordered it for me. I think I paid in the $25 range, retail. The
thing is solid as a rock and very well built. I was never worried
about the stem breaking off from the vibration.

Anyway, the price was really good as well. A buddy of mine repeated
what I did, and they sampled him the one he wanted. Link is
http://www.nasonptc.com/pressure_switches.html You pick out the
pressure range, connection type, etc, rather than figuring out how to
make what's on the market wire up to your existing system. They also
have adjustable ones, too.