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Topic: Checking water level in an electric kettle (Read 2 times) previous topic - next topic

jrmedd

Hi all,

So I've been looking at this thread: http://forum.arduino.cc/index.php/topic,14691.0.html trying to work out how best to measure how much water is in my kettle before switching it on remotely.

One of the solutions offered in the aforementioned thread is to probe the water with two wires and measure conductivity via an analog pin. I've seen this technique used for moisture measuring elsewhere too, but I'm not sure how well it will play with two key factors in the kettle scenario:

1) It contains drinking water, which I don't want to contaminate.

2) It'll get very hot, so I'm not sure how that'll affect things.

Any recommendations for monitoring the water level in any electric kettle?

mirith

While maybe not ideal, possibly a floater of some form (easily kept clean/safe), that has a magnet in it with a series of reed switches on the outside.  However you do have temperature issues since the water will be warmer than most consumer electronics (thus a higher ambient temperature).  Otherwise maybe a sensitive water pressure sensor and some calibration curves.

bigred1212

Maybe there is a way to reframe the problem??

If the kettle is left empty each time, you know that quantity=0 at all starts.  When you want to switch it on, the turn-it-on process instead both adds a known quantity of water (pump?) and switches the heat on.  This might avert the the problem of measuring an unknown quantity.

Just a thought. 

mmcp42

you could just measure the rate of change of temperature
fast rise = not much water
slow rise = enough water
there are only 10 types of people
them that understands binary
and them that doesn't

PeterH

I only provide help via the forum - please do not contact me for private consultancy.

radman

The scales and the magnet both sound good. Most kettles have a visible level gauge, you could just train a webcam on it.

jrmedd

#6
Jul 03, 2013, 02:49 pm Last Edit: Jul 03, 2013, 02:52 pm by jrmedd Reason: 1
Thanks for all of the replies.

An external solution such as weight/load sensor sounds like a brilliant plan. Any recommendations on that?

To clarify the project (if anyone's interested): my remote input will be offset by how far I am from the kettle - determined by GPS on my phone - how much water is currently in it, and the temperature.

Henry_Best


Thanks for all of the replies.

An external solution such as weight/load sensor sounds like a brilliant plan. Any recommendations on that?

To clarify the project (if anyone's interested): my remote input will be offset by how far I am from the kettle - determined by GPS on my phone - how much water is currently in it, and the temperature.


Temperature of the water in the kettle or the external temperature (or both)? You're unlikely to want a hot drink if it's over 80 degrees F outside! Cold water takes longer to boil.

wizdum

Would you be able to use something like an ultrasonic sensor? I'm not sure if it will give you an accurate reading bouncing off water.
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dc42

Is it a metal or a plastic kettle? If it is a metal kettle then a vertical stainless steel wire inside the kettle could be used. Measure the resistance between the wire and the kettle body, which will be grounded. However, limescale buildup on the wire may be a problem. If it is a plastic kettle, put a vertical strip of metal foil on the outside and measure the capacitance to ground. Search the forums for nichrome and capacitive sensing to find a thread about this. The weight sensor also sounds like a good idea to me.
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jrmedd

I think I've decided on the weight sensing idea, although I'm not sure how best to go about it. I've seen some examples using a Flexiforce sensor, but the requirement for regular calibration might scupper me.

If I use a load sensor I understand I'll need some sort of an amplifier?

PeterH


I'm not sure how best to go about it


Buying complete scales would probably cost a lot more that just buying the sensor, but if you don't mind spending $60-70 it would make the project a heck of a lot easier.

http://learn.adafruit.com/digital-shipping-scales/
I only provide help via the forum - please do not contact me for private consultancy.

dc42


If I use a load sensor I understand I'll need some sort of an amplifier?


Yes. A single supply instrumentation amplifier such as INA122 would be easiest to use.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

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