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Topic: any Ideas what kind of sensor this is? (Read 212 times) previous topic - next topic

BulldogLowell

Nov 15, 2017, 01:36 pm Last Edit: Nov 15, 2017, 01:37 pm by BulldogLowell
I'm doing a project that I would like to be able to sense a human hand through vitreous china like this sensor.

Does anyone know what kind of sensor it is?  There are no FCC markings on the box (USA model)


Delta_G

I'd bet it is a capacitive sensor but I'm just guessing. 
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wvmarle

Image on the packing makes me think IR based proximity, but if it's sensing through the lid it just has to be capacitive.
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Power_Broker

Since it is "touchless" I doubt it is capacitive and IR doesn't make any sense to me. Looking at the actual module and knowing it it touchless, I would of say it is an ultrasonic sensor (in the same form factor as a car backup ultrasonic sensor).
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BulldogLowell

...I would of say it is an ultrasonic sensor (in the same form factor as a car backup ultrasonic sensor).
not likely ultrasonic, sound  through air, through porcelain back through air, reflected off of skin, back through the air to the porcelain and so on...

It is definitely an electro-magnetic field but I cannot disrupt/trigger it (yet) with a coil.

I figured it it used microwaves, it would have to have an FCC license so that leads me to think it is capacitive.

capacitive sensors may not require a touch... by the way.



jremington

It would be quite a sophisticated capacitive sensor that could sense a human hand from that distance, and yet deal with changing water levels in the tank.  Perhaps problems with the sensor might explain the "phantom flush" that has been reported for this unit.

Take it apart and let us know what you find!

cattledog

From some Kohler literature
Quote
"Unlike a beam-based sensor, in which a beam of light is broken to trigger the actuation, the Kohler Touchless flush utilizes emerging sensing technology, which projects an electromagnetic field that is both extremely accurate and reliable. This type of sensor detects the user in the projected field and initiates the flush."
Here's a wikipedia link on Electric Field Proximity Sensing
https://en.wikipedia.org/wiki/Electric_field_proximity_sensing

jremington

#7
Nov 16, 2017, 07:58 pm Last Edit: Nov 16, 2017, 08:00 pm by jremington
As a followup to cattledog's post above on Electric Field Proximity Sensing, there is this very interesting Ph. D. thesis on "electric field imaging", which can be used to detect movement of humans through low frequency electric fields.

Still, changing water levels in the tank could be a problem.

BulldogLowell

#8
Nov 16, 2017, 08:43 pm Last Edit: Nov 16, 2017, 08:43 pm by BulldogLowell
Still, changing water levels in the tank could be a problem.
It seems like it is very directional.  that is, a wave over the top of the device is the only triggering event.  Perhaps plenty of filtering....

we've been testing this one on amazon, which we've not seen any phantom flushes in over two weeks of use.


Delta_G

Quote
Still, changing water levels in the tank could be a problem.
Unless something is wrong with the toilet, the water level shouldn't be changing except during a flush or right after while it's filling back up.  That could be handled by simply locking it out for a time after each flush. 
If at first you don't succeed, up - home - sudo - enter.

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