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[General] Water level senso for kettle

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piotr_jan

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Water level sensor for kettle

Hi. I am working on an uC kettle and have a problem with water level sensor. It has to be something very simple, reliable and temperature resistant. It does not have to be to precise as it only is used as a guide for the micro. Have you heard about such a sensors?

Thx
Peter
 

Re: Water level sensor for kettle

Hi

I think a simple magnetic float switch is quite good for your purpose. it has a floating part with magnet sealed on it and comes up and down . when th water level reaches the desired level the floating part comes up makes a reed relay to close and that can be used to detect with uc.

something like this : Untitled.jpg
 
Thank you - but i think it is to big for me. I think that the limescale will be a problem as well. Actually I have no idea how to measure the water level in the kettle.
 
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It is a reliable and direct method if you use a float switch of some kind.
But perhaps the water is for drinking? Then it may be distasteful to drop objects into it.
So perhaps an optical sensor is suitable.

7229877000_1474828210.gif


The beam strikes a different detector, depending on the liquid level.
 

I don't think you will find a sensor that will be cheap and reliable that works at ~100C.

By far the easiest and cheapest method is to weigh it. Weigh the empty kettle and subtract it from the weight with water in it. I think we know how much water weighs so the volume calculation is easy.

Brian.
 

Float switch is industry standard solution e.g. for steam generators or engine oil pans, designed for > 100 °C. If the sensor must be very small, I would think about capacitive or conductive sensing.
 

There are all sorts of problems here.
Minimal water depth, extreme boiling turbulence, steam, heat, it a pretty hostile place in there.

My approach would be a horizontal stainless steel probe a few mm above the floor of the kettle. That would be connected to the gate of a mosfet and a very high value pullup resistor to the +ve dc supply.

When the kettle boils dry the pullup resistor turns on the mosfet.
With the probe submerged, the water "shorts" the gate down to ground and the mosfet remains turned off.

The probe could be a "L" shape or "U" shape supported up high, with the lower horizontal part at the required water detection height.
 

Hi Sorry for the long delay, and thank you for help. Actually I have sorted it another way: I just measure the temperature of the heating element and the speed of changes indicates the water level. Accuracy is good enough for the kettle (about +-15%)
 

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