I'm looking for a 120VAC proximity switch, SPST NO, something like alarms
use on doors and windows. Has anyone seen anything like this?

The application is to determine if an x-ray shield is in place.
Unfortunately there is no AC in the area to be able to use a relay and low
voltage sensors. There are just the two wire that need to be shorted when
the shield/door is in the correct position. The previous solution was a reed
switch, but the geometry of the shield/door makes this a very difficult
solution and the sensor get's destroyed if the user doesn't manipulate the
shield correctly. I'm hoping to change to a proximity senor to keep this
from happening again.

Thanks,
Bernie

"Bernie Hunt" wrote in message
...
I'm looking for a 120VAC proximity switch, SPST NO, something like alarms
use on doors and windows. Has anyone seen anything like this?

The application is to determine if an x-ray shield is in place.
Unfortunately there is no AC in the area to be able to use a relay and low
voltage sensors. There are just the two wire that need to be shorted when
the shield/door is in the correct position. The previous solution was a
reed switch, but the geometry of the shield/door makes this a very
difficult solution and the sensor get's destroyed if the user doesn't
manipulate the shield correctly. I'm hoping to change to a proximity senor
to keep this from happening again.

Thanks,
Bernie





Bernie,

Perhaps an optical sensor using a reflective tape target, an ultrasound
sensor which measures a nearby shield's reflection / echo, a ferric /
magnetic sensor if the shield has any iron / ferric content, or some other
form of non-contact approach or, instead, a weight sensor which relies on
the mass of the shield / door using a solid state or other strain gauge?

Smarty

On Thu, 23 Oct 2008 20:23:30 -0400, "Bernie Hunt"
wrote:

I'm looking for a 120VAC proximity switch, SPST NO, something like alarms
use on doors and windows. Has anyone seen anything like this?

The application is to determine if an x-ray shield is in place.
Unfortunately there is no AC in the area to be able to use a relay and low
voltage sensors. There are just the two wire that need to be shorted when
the shield/door is in the correct position. The previous solution was a reed
switch, but the geometry of the shield/door makes this a very difficult
solution and the sensor get's destroyed if the user doesn't manipulate the
shield correctly. I'm hoping to change to a proximity senor to keep this
from happening again.

Thanks,
Bernie


Do you know how much current you need to control? If it's not too
much, say 200-400 ma, you can use an AC prox switch.

www.mcmaster.com search for AC proximity Switch. They are available
in NC and NO and change state when close to a metal object.

More $$ than a reed or mechanical limit switch, but very reliable.

If you need more current, just use a mechanical limit switch.

HTH,

Paul F.

Bernie Hunt wrote:
I'm looking for a 120VAC proximity switch, SPST NO, something like alarms
use on doors and windows. Has anyone seen anything like this?

The application is to determine if an x-ray shield is in place.
Unfortunately there is no AC in the area to be able to use a relay and low
voltage sensors. There are just the two wire that need to be shorted when
the shield/door is in the correct position. The previous solution was a reed
switch, but the geometry of the shield/door makes this a very difficult
solution and the sensor get's destroyed if the user doesn't manipulate the
shield correctly. I'm hoping to change to a proximity senor to keep this
from happening again.

Thanks,
Bernie


There are industrial limit switches that will handle
the voltage. You might look at a limit switch that
has a nylon rod or flexible spring actuator. I've
used the nylon rod type and the rod can bend all sorts
of ways without damage. Google "nylon rod limit switch".

TDD

In article ,
"Bernie Hunt" wrote:

I'm looking for a 120VAC proximity switch


Unfortunately there is no AC in the area

Thanks,
Bernie

You sound a little confused, Bernie.

Smitty,

"no AC in the area" meaning a complete circuit with a hot wire and a neutral
so I could run a transformer. I have two wires in the box but neither are a
neutral, so no complete AC circuit. The switch makes contact on the hot side
of a cirucit that runs on 120VAC, therefore I need a high voltage switch.

Think of this like light switch boxes in older houses where they didn't pull
neutral wires. Does this make sense now?

Bernie


"Smitty Two" wrote in message
news
In article ,
"Bernie Hunt" wrote:

I'm looking for a 120VAC proximity switch


Unfortunately there is no AC in the area

Thanks,
Bernie

You sound a little confused, Bernie.

Not knowing your profession, I'll point out that there's a whole world
of 'industrial controls' from people like Omron, Square-D,
Allen-Bradley. (It's been a long time since I was involved, so the
names may have changed.)

But, it sounds like you want a non-contact, line-voltage, proximity
switch that operates without power. (ie, the absent neutral.) It's not
my area of expertise, but I think the pickings will be slim - maybe just
reed magnets.

Finally, I don't know if this is a cross-post, so I'll also suggest
sci.electronics.design. Not their primary focus, but there's a lot of
knowledge there.

G


On Thu, 23 Oct 2008 20:23:30 -0400, "Bernie Hunt"
wrote:

I'm looking for a 120VAC proximity switch, SPST NO, something like alarms
use on doors and windows. Has anyone seen anything like this?

The application is to determine if an x-ray shield is in place.
Unfortunately there is no AC in the area to be able to use a relay and low
voltage sensors. There are just the two wire that need to be shorted when
the shield/door is in the correct position. The previous solution was a reed
switch, but the geometry of the shield/door makes this a very difficult
solution and the sensor get's destroyed if the user doesn't manipulate the
shield correctly. I'm hoping to change to a proximity senor to keep this
from happening again.

Thanks,
Bernie

In article ,
"Bernie Hunt" wrote:

Smitty,

"no AC in the area" meaning a complete circuit with a hot wire and a neutral
so I could run a transformer. I have two wires in the box but neither are a
neutral, so no complete AC circuit. The switch makes contact on the hot side
of a cirucit that runs on 120VAC, therefore I need a high voltage switch.

Think of this like light switch boxes in older houses where they didn't pull
neutral wires. Does this make sense now?

Bernie



Got it, thanks for the clarification. I'm having trouble visualizing the
gadget and the problems associated with it. Isn't a reed switch a
"proximity sensor?" Why can't that work now? How about a micro switch?
What about a mercury switch? Or a battery operated emitter-detector with
relay?

"Bernie Hunt" wrote in message
...
Smitty,

"no AC in the area" meaning a complete circuit with a hot wire and a
neutral so I could run a transformer. I have two wires in the box but
neither are a neutral, so no complete AC circuit. The switch makes contact
on the hot side of a cirucit that runs on 120VAC, therefore I need a high
voltage switch.

Think of this like light switch boxes in older houses where they didn't
pull neutral wires. Does this make sense now?

Bernie


"Smitty Two" wrote in message
news
In article ,
"Bernie Hunt" wrote:

I'm looking for a 120VAC proximity switch


Unfortunately there is no AC in the area

Thanks,
Bernie

You sound a little confused, Bernie.




Pick one
http://www.grainger.com/Grainger/wwg...elected=Switch

Thanks everyone for thier input!

The general problem with a regular type switch is that it has to be
triggered when the shield is swung into it's correct place, but has to let
the shield over swing it's correct place and not trigger.

TDD get the cookie prize for this one. Both Grainer and MSC have a number of
whisker tipped limit switchs that I think will do the job. I have to call
MSC on monday to make sure their less expensive model has a normally open
condition. (It seems normally closed is normal for limit switches, at least
that's what Double D's catalog implies) If they do, then that's the chose.
If not, then its the more expensive Telemecanique model from Grainger, but I
figure it's worth waiting till monday to maybe save $50.

Thanks again everyone, it's great to have a resourse of thinking minds to
access.

Bernie

"The Daring Dufas" wrote in message
...
Bernie Hunt wrote:
I'm looking for a 120VAC proximity switch, SPST NO, something like alarms
use on doors and windows. Has anyone seen anything like this?

The application is to determine if an x-ray shield is in place.
Unfortunately there is no AC in the area to be able to use a relay and
low voltage sensors. There are just the two wire that need to be shorted
when the shield/door is in the correct position. The previous solution
was a reed switch, but the geometry of the shield/door makes this a very
difficult solution and the sensor get's destroyed if the user doesn't
manipulate the shield correctly. I'm hoping to change to a proximity
senor to keep this from happening again.

Thanks,
Bernie


There are industrial limit switches that will handle
the voltage. You might look at a limit switch that
has a nylon rod or flexible spring actuator. I've
used the nylon rod type and the rod can bend all sorts
of ways without damage. Google "nylon rod limit switch".

TDD