[neilep (OP)]

Dearest Door Releaseologists !...Ewe know who ewe are !...Hanging around door release mechanisms all day dreaming up new ways to release doors !!..oh yes !!

Lookee here.........here's one for ya !!

 [ Invalid Attachment ]

A Door Release Mechanism Being A
 Door Release Mechanism Earlier Today !





Nice eh ?...as far as door release mechanisms go..this ones a real looker eh ?...it's well fit !!


As a sheepy who works in a place that uses one of these mechanisms I would like to know why ,that where it says 'Touch ' ..that my finger need not actually make contact with it for it to work...however...any other non finger/appendage object must make contact with it !

Why's that then ?...Why Does This Door Release NOT Require Contact From My Finger But Does Require Contact From Non Organic Stuff ?




Hugs and shmishes

mwah mwah mwah !



Neil
Touché
xxxxxx

[imatfaal]

Same reason an iphone will not respond to any input with a fingernail or pen; but will to a nose, finger, or other sheepy appendage that is fleshy

[neilep (OP)]

Same reason an iphone will not respond to any input with a fingernail or pen; but will to a nose, finger, or other sheepy appendage that is fleshy

Thanks Imatfaaly chum !  []...Thing is ..This DOES operate with the touch of a pen or side of phone as well as the closeness (but no need for physical contact) of a fleshy appendage !..oooerrr !!

[Geezer]

Maybe it's a "heat seeking" button. What happens if you are wearing gloves (other than gettting warm hands)?

[CliffordK]

Or...
you could dangle an ice cube from a string.  See if it likes that.

It could sense movement although I don't see an obvious aperture.  Perhaps sonar. 

I've seen similar wireless badge readers, but that is a whole different device.

[Geezer]

It could be similar to this

http://www.smarthome.com/77410/Enforcer-Single-Gang-No-Touch-Request-to-Exit-Sensor-Switch/p.aspx

[RD]

My money is on capacitance (rather than IR) ...



http://pcbheaven.com

[Geezer]

My money is on capacitance (rather than IR) ...



http://pcbheaven.com

Maybe, but I rather doubt it. The sheepy appendage at a distance of a couple of inches would not present much capacitance to ground. If it was sensitive enough to detect the difference it would tend to get confused easily by electrical interference and humidity.

(We may need to get Neil to dismantle the thing and send us piccys to solve this one.)

[RD]

... The sheepy appendage at a distance of a couple of inches would not present much capacitance to ground. If it was sensitive enough to detect the difference it would tend to get confused easily by electrical interference and humidity.

Yes if set too high it would be triggered at a distance, somewhat like an L-C circuit metal detector, (but with a fleshy object affecting C rather than a metal one affecting L) ...

A capacitance switch needs only one electrode to function. The electrode can be placed behind a non-conductive panel such as wood, glass, or plastic. The switch works using body capacitance ... When a person touches it, it increases the capacitance and triggers the switch ... These devices can also be used as a short-range proximity sensor.

https://en.wikipedia.org/wiki/Touch_switch#Capacitance_touch_switch

https://en.wikipedia.org/wiki/Capacitive_sensing

[Geezer]

Here you go!

http://www.jwsltd.co.uk/touch-to-exit-touch-switch-178-p.asp

(Don't waste your time downloading the data sheet.)

[neilep (OP)]

Maybe it's a "heat seeking" button. What happens if you are wearing gloves (other than gettting warm hands)?

This is a great suggestion Dr Geezer...next time I am at this locale within my place of work I will wear my gloves and will report back here asap !...I know ewe can barely contain your eagerness-to-know but please be patient !  []

[neilep (OP)]

Or...
you could dangle an ice cube from a string.  See if it likes that.

It could sense movement although I don't see an obvious aperture.  Perhaps sonar. 

I've seen similar wireless badge readers, but that is a whole different device.

Thank ewe Monsieur CliffordK...I'd luff to try the dangling ice cube from a string test but they'd think I'm one of those new age hippie crystal peeps and I can't risk that !....

Ewe are right..there is no aperture.

Sonar ?..I will check....perhaps I have been remiss in my observation skills and not realised that my pace of work is a submarine !!  []...It happens ewe know !

[neilep (OP)]

It could be similar to this

http://www.smarthome.com/77410/Enforcer-Single-Gang-No-Touch-Request-to-Exit-Sensor-Switch/p.aspx

I would dearly luff it to be one of those but it needs to be in very close proximity..say..a few mm for the non-contactness to work !...Thanks though !

[neilep (OP)]

My money is on capacitance (rather than IR) ...



http://pcbheaven.com

Gosh !..that could be it...thanks RD

[neilep (OP)]

Here you go!

http://www.jwsltd.co.uk/touch-to-exit-touch-switch-178-p.asp

(Don't waste your time downloading the data sheet.)

Woo !!...looks like ewe have found the actual  item !....sheesh !!..Only £21 !!!.....don't these people know who they are dealing with here ?....Someone's going to get fired about this !  (probably me !...DOH !!)

[SeanB]

Capacitive touch switches work by sensing the slight increase of current caused by you approaching the sensor plate. The plate is driven with a high frequency signal through a very high resistance, so that it is going to have the same signal level as the drive side when the plate is untouched. If you come near with your body the plate forms a very small capacitor, one plate being the sensor, the other being you connected to ground ( either because you are barefoot on an antistatic floor or you having a much larger capacitor formed by your feet and shoes to the floor) with the dielectric being air and the front plastic cover. This small capacitance is enough to lower the signal level and this is detected to operate the door.

There are trade offs between the size of plate ( a bigger one means you only have to come near the sensor to trigger it) and sensitivity ( a bigger plate is more prone to false triggering caused by moisture films forming inside or outside the sensor housing, so often they are either heated by a dedicated low wattage heater or the power supply is designed to do the same heating as well) along with how robust and vandal resistant they are. These can be made very tough, such that it is almost impossible to damage them without tools.

[Geezer]

If I was a "no touch" sensor, would you hold it against me?

(Good grief, I just realized the VAT on that thing is 20%!!)