Backyard Aquaponics
A place to discuss aquaponics

One place I use to work had a commercial coffee maker hooked to the water line (like a refrigerator). It held a pots worth of water in it at all times, and monday morning you would only get half a pot because of evaporation over the weekend. You pushed a button to start it making coffee.

My question is: it somehow knows how much the coffee pot can hold, how does it know when to stop brewing and when to stop refilling itself with water? It can't always float the water refill or it would overflow the pot and never stop brewing.

umm could be a couple of things. depends on where the water was connected. most probable, is that it had a sonar level detector installed, that sensed the level of the coffee. these are worth about $1 to manufacturers, so it wouldn't be pricey
level can also be measured by pressure, electrical conductivity, floats on potentiometers. But for this application, I'll be betting on ultrasonic.

I expect there must be some sort of clockwork timer that functions on the assumption of a particular flow rate on the inlet. When you brew a pot of coffee, it then re-fills the storage chamber for the set length of time it takes to get a pot full of water ready for the next brew. We know it isn't a float valve since the evaporation doesn't cause it to top up over the weekend.

This is only an auto fill in that it fills back up after some manual action is taken. Pushing the button to start brewing the coffee. Or like the toilet flush, it fills back up after you flush.

There are ways to make a toilet flush valve work as an automatic flood and drain device though.

Our coffee maker here at work starts re-loading the reservoir at the top when it is brewing and also when you use the tap for hot water for tea. There must be some pressure or vacuum mechanism to reload it automatically when the heat is on. It would be worthwhile to get a broken one and open it up to find out how it works...

A toilet start refilling the second it starts flushing. The coffee pot (I'm guessing) doesn't start refilling until it has become empty (hence the half a first pot on monday). Maybe like an autopot smartvalve? Or perhaps a moisture indicator/scale near the bottom with a float cutoff at the top? Could be timed inlet too but that would seem more cumbersome for installation.

Being that I imagine the pot is removable, and has no connections on the bottom (imagined a glass just style) I'm sure it would measure the level from the top. Non contact is better for health reasons, and there are only a couple of ways to do that.
Ultrasonics could give a 'low' reading, and measured flow could ensure no overfilling. It's the cheapest most reliable solution I can think of.

What about a load cell ?

weight... yes that's true...
a loadcell (electronic scale) would have to be 'imprecise' or the action of removing and replacing the pot could overload it and blow it up, but if we're talking 2kg with 100g variance it's not too bad, and it will fill to within 100ml of the same place every time.
It's continuous (so it can give a varying output easily for half full, empty etc) and it's reasonably cheap.
I'm starting to like a loadcell for this app.

PS is this just curiosity? or are we looking at a cool invention imminent?

Whatever the sensor is, it is on or measuring an internal compartment for the water waiting to be heated, not the coffee level in the craft.

The question is, how does it not overload the jug, when the jug is half full already.
It must be sensing the jug.

No the auto fill doesn't fill the coffee jug. It fills a holding tank in the machine what will then heat the water the next time a fresh pot of coffee is to be made. So it must re-fill that holding tank right after a fresh pot of coffee is made and if there is a long period of time since the last pot of coffee was made, the evaporation will leave you with only a half pot of coffee being made after the weekend since the tank hasn't re-filled since Friday morning and it's just been sitting there.

autopot

It was more of a curiosity thing to see if any good ideas could develop from it. AP is always looking for ways to alternate drain and fill and regulate the timing of them.

Hmmm really? Then I completely misunderstood the entire problem

My Boema has a circuit board that controls the water. But this one is under pressure all the time and has a high pressure pump to get the water into the steam chamber. Pressure and temp sensors. Nice coffee tho.