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Need ideas to prevent steam influencing Proximity sensors

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userx2

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I am having huge issues with steam condensation influencing my Proximity values from my IR sensors.
I have not found any usable solution.
Problem is that this sensor sits over a kitchen sink.

Perhaps someone else out there has some creative ideas?

Regards
X
 

stenzer

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Hi,

are you interested in a solution for your existing IR sensor or an alternative? An ultrasonic sensor migt be a suitable replacement as it can be used to determine proximity and it is not prone to steam.

BR
 

KlausST

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Hi,

What about a magnet and a reed relay,
Or an inductive sensor and metal
Or a mechanical switch
....

Klaus
 

userx2

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Ok,
Not quite. I have a pcb design with multiple IR sensors on it for an application.

They need to detect 3 levels of range from a person's hand.
So a reed switch will not work.

I have looked at ultra sonic but I am not sure I can get them in a pcb mount smd miniature component.

What do you think?
 

stenzer

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Hi,

there are SMD ultrasonic transducers available e.g. [1], but with abaout 25 USD at digikey they are pretty pricy.

Is the steam itself causing troubles as the wavelength of the emitted light is in the range of the size/diameter of the steam/water "droplets"? This is a common issue for optical communication links operated in foggy environments. Or is the condensate on the surface of your IR sensor an issue?

[1] **broken link removed**

BR
 

userx2

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Unclear exactly what the physics behind the trouble is.

I observe the proximity values dropping a lot from the baseline when the puff of steam hits the windows (call it negative).
Thereafter, it becomes totally unpredictable in that the values suddenly flip positive into the normal detection ranges and then negative again, etc.
This is with just a single 2second puff of steam.
This can last up to 55 seconds.

It is the condensation doing it (fog on IR window). Although that dissipates in a few seconds and the window looks dry, the values stay upset.

I have no explanation why the values go negtative instead of the expected positive. It is as if the window becomes more transparent.
 

stenzer

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Hi,

it might be helpful if you upload a picture of your measurement system as well as a schematic of the circuitry. Of special interest is the used IR sensor.

I assume your circuitry is well sheltered by an apropriate housing. Although destilled water should be (ideally) electrical non-conductive, it is still a little bit conductive (conductivity increases with higher frequencies and depends on temperature).

BR
 

Akanimo

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Hi,

Please give more info about your sensor.
 

userx2

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Sensor is Vishay VCNL4020.
There is a IR filter cover window on the housing.

The window gets the condensation problem.

I am looking at heating the IR cover windows but I worry about the additional energy use 24/7/365 just to heat 4 windows.

Technically this is also a huge challenge because the window is a plastic / silicon combination and is curved.

Thanks for the suggestion of the transparent heaters. I will look into it

x
 
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stenzer

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Hi,

something you migth try is how the sensor is affected by smoke i.e. from a cigarette. There are smoke detectores utilizing IR sensors based on the scattering of smoke particles. If your IR sensor shows a similar behaviour as mentioned previously, you might include the vapour as a contributing problem. Or using a pump sprayer to create some small water droplets in the vicinity of your sensor (do not spray the water on the sensor).

BR
 

stenzer

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.... you may also cover the sensor with a little bit of water, to imitate the effect of condensated water.

BR
 

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