Hi , i want to set a 3 levels sensor for a drinking water in a kettle,the water is dispensing from the kettle to a cup; the two high levels have a led for indication and the low level have an output to Arduino to run a small pump, by the way, i want to use an ultrasonic sensor but it will be destroyed by the vapor from the hot water and the capacitive sensor is expensive, so how can i do that?
Can You measure the level when it is cold, before heating it? Then an arrangement using a float carrying some sensors could work.
Railroader:
Can You measure the level when it is cold, before heating it? Then an arrangement using a float carrying some sensors could work.
It's not a practical way, i need measure the temperature then measuring the level , i need a method that works in boiling temperature
you could put 4 aluminium probes into the water 1 common and 3 for each of the levels that you want to test at.
3 level probes will be connected to the base of 3 transistors through a current limiting resistor. collectors would have a resistors connected to +ve . common probe would be connected to +ve and go to below all other probes.
emitter would have led's for indicator or would go to Arduino.
resistors would need to be calculated when you've built the circuit as would depend on how far apart the probes are and the type of water.
different areas have different water and this will change the resistance. don't go down this road if you are using pure water as it doesn't conduct as good.
Measuring temperature is one matter. Is the kettel refilled or drained during heating?
suttle0577:
you could put 4 aluminium probes into the water 1 common and 3 for each of the levels that you want to test at.3 level probes will be connected to the base of 3 transistors through a current limiting resistor. collectors would have a resistors connected to +ve . common probe would be connected to +ve and go to below all other probes.
emitter would have led's for indicator or would go to Arduino.
There is a problem of electrolyzes;
Railroader:
Measuring temperature is one matter. Is the kettel refilled or drained during heating?
When heating is finished the water is dispensing to cup of the user .
The circuit wouldn’t need to be on all the time. The Arduino would turn it on and off. Would only need to be on for a split second when reading.
I would put a load sensor under it and you can tell near exact how much water is in it by the combined weight.
Capacitive sensors are not expensive - the equivalent of maybe 5 USD a piece - and can measure from the outside of the kettle. That will do the job for sure. You can also construct them quite easily yourself, for little money - just some pieces of aluminium foil are needed (on the outside of the kettle).
Aluminium sensors inside will be electrolysed over time, stainless steel will do a lot better. A cheap solution, but only suitable for a short term demo.
But the kettle as you show on the image is the type that's supposed to be picked up from its base, and moved around. That doesn't go well when there are sensors wired to it, and that's another vote for the weight sensor in the base.
Slumpert:
I would put a load sensor under it and you can tell near exact how much water is in it by the combined weight.
wvmarle:
But the kettle as you show on the image is the type that's supposed to be picked up from its base, and moved around. That doesn't go well when there are sensors wired to it, and that's another vote for the weight sensor in the base.
That is a good idea , the weight of the kettle is about 1kg and the max volume of the water is 1.7L so the weight of both is 2.7kg, so i will take a load sensor > than 2.7kg, but i have found many load sensor from 3kg to 20kg , i don't know which one i will take it ? and what is the difference between them?
A 3-5 kg one will do.
Higher range means lower resolution normally.
There will be difference in how you interface with them, stability, accuracy, etc... read the data sheets. Typical strategy: make a short list of those that fulfil your requirements, and get the cheapest of those.
You can always use a 2.2kilo bar weight as base plate...
Or since this is such a lightweight project a force resistor would be useful in your range.
An FSR would be able to tell you whether the pot is more than half full or not. With some calibration you may get a bit higher precision, like 1/4 full steps, but not too much more than that.
If that's good enough for OP, it'd be a fairly inexpensive solution indeed, though he'd still need at least three of those sensors to make sure the full weight of the pot is carried by them (and then calculate the total weight using the output of the three of them).
Yep. Maybe weighing would be the best option. If it were that easy to monitor the kettle water level using sensors ..... cheap and reliable etc, they probably would have it on the market by now. Worth trying though. Since the feature would be quite nice.
If the scales/weight method is used, then probably need to make sure that the vibrations of the kettle don't interfere with the readings too much. Maybe ok.
Should be easy to filter out.
Fast movements: ignore the readings entirely (it's quite safe to assume that the water level doesn't change much during the boiling process). Maybe do a long time average, like a couple hundred readings, should also give a good overall number.
Slow movements, or big steps: pot removed/replaced; water filled/drained.
OTOH a capacitive sensor should be pretty cheap and easy to implement (strip in the side of the pot), and they're pretty reliable as well. Retrofitting one in a kettle is of course much harder than adding it from the get go, and connecting it to the electronics in the pot itself (some wireless kettles have electronics in the kettle itself, which then only work when it's placed on the base, as that's where they get the power from).
wvmarle:
(some wireless kettles have electronics in the kettle itself, which then only work when it's placed on the base, as that's where they get the power from).
Excellent points wvmarle. The retrofit could be tricky. I agree. The idea of coming up with a nice way to reliably measure the water level is a decent challenge. Nice projects could come out of this.
Thanks all, I had bought a 5kg load cell