

Show HN: Cookoo – Whistle Counter for Pressure Cookers - sagargv
http://s-gv.github.io/cookoo/

======
srean
I have noticed that pressure cookers are often not used efficiently. Its quite
common to run them on high flame or heat throughout. This is wasteful. Once
the water starts boiling in that high pressure, the interiors are a constant
pressure constant pressure system. The heat needed to sustain it is
surprisingly and significantly lower, just need to cover for the losses. All
that extra heat is just heating your kitchen. This is relevant to the
discussion because whistle count is strongly dependent on the flame: too high
and you would need more whistles, rather counterintuitive. A timer that's set
off after the first whistle would be closer to what one needs. Finally too
cook fast, set the flame high till the first whistle and then let it simmer

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baxter001
Is the whole whistle counting thing typically an Indian usage of a pressure
cooker?

I often see whistle counts mentioned in recipes from the country but all of
the more local recipes I have seen relied more upon strict timings.

~~~
tomkinstinch
American here. I've never heard of this usage of pressure cookers, and I'm not
sure I really understand it. Can anyone explain why whistle counting works?

Does the pressure-temperature relation of the combined gas law hold in the
steam regime, considering the weight clamps the cooker to a maximum pressure?
It seems like the whistle frequency would be a function of heat input to the
system (or rather heat lost) while temperature would mostly be determined by
the letoff pressure value. You'd think a longer time or higher temperature
would shorten cooking time, not the amount of heat escaping the system. Below
the letoff pressure, temperature is a great proxy for pressure (via the
combined gas law), and indeed this is how many of the electric pressure
cookers "sense" pressure; they have thermistors thermally coupled to the cook
pot. Could it be that pressure recovers to the letoff value more quickly at
higher temp? That would make whistle counting for temperature roughly similar
to the light measurement method of the modulo camera that was discussed a
couple days ago[2]. It seems like the diameter of the pot might impact
pressure recovery time though.

All that said, it is GREAT to see more cooking tech, OP. Anything that helps
people to cook more (or better) can only be a good thing.

Perhaps worth knowing is that there are three types[1] of pressure cookers,
and it seems like OP's product could only potentially work for one (?) of
them: old-school weight-clamped. Fagor-type pressure cookers release steam
constantly, old-school weight-on-top pressure cookers release steam
intermittently, and Kuhn Rikon pressure cookers release no steam at all (best
for flavor since no volatiles are lost to the kitchen with escaping steam).

1\.
[http://www.cookingissues.com/index.html%3Fp=2561.html](http://www.cookingissues.com/index.html%3Fp=2561.html)

2\.
[https://news.ycombinator.com/item?id=10053691](https://news.ycombinator.com/item?id=10053691)

~~~
baxter001
By that reasoning determining cooking time by the number of whistles would be
a very coarse and inaccurate measure of "time spent at optimal cooking
temprature" very sensitive to heating temperature.

If the weighted valve and letoff system is succeeding in staying close to a
constant pressure/temperature surely a simple timer would be a better
solution.

------
cstrat
I didn't know that this is how other pressure cookers worked.

Mine just releases steam constantly through a valve once it gets to a certain
temperature/pressure... but I might just be using it wrong :P

~~~
bgdam
I think your safety valve is gone. The safety valve should not be releasing
pressure constantly once the whistle is on top of the lid.

~~~
tomkinstinch
That's not necessarily true; there are three types of popular pressure
cookers[1]. Fagor-type pressure cookers release steam constantly (this could
be the kind GP has), old-school weight-on-top pressure cookers release steam
intermittently (this may be what you have in mind), and Kuhn Rikon pressure
cookers release no steam at all (this third type is best for flavor since no
volatiles are lost to the kitchen with escaping steam).

1\.
[http://www.cookingissues.com/index.html%3Fp=2561.html](http://www.cookingissues.com/index.html%3Fp=2561.html)

~~~
batbomb
Correction: They release steam if they are over-pressure, but that's not
supposed to happen in normal cooking conditions

------
rbosinger
It's neat to see someone solve a problem that you didn't have any clue existed
in the first place.

I have a pressure cooker that I've never used. Am I understanding (from the
rest of this thread) that I could be attempting to make some sweet Indian
dishes with it?

------
paddi91
Would it be possible to release the PCB and schematic source files?

~~~
sagargv
They are in the repo:

Schematic -
[https://github.com/s-gv/cookoo/blob/master/schematic/whistle...](https://github.com/s-gv/cookoo/blob/master/schematic/whistle_counter.png)

PCB -
[https://github.com/s-gv/cookoo/tree/master/pcb/gerber](https://github.com/s-gv/cookoo/tree/master/pcb/gerber)

~~~
fordh
These aren't really the source files, because they aren't easily editable. I
believe the parent was asking for the KiCad files.

~~~
sagargv
KiCAD files:

[https://dl.dropboxusercontent.com/u/53155453/cookoo_kicad.zi...](https://dl.dropboxusercontent.com/u/53155453/cookoo_kicad.zip)

Not sure if this is the latest version.

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a8da6b0c91d
If tending the stove is a problem why wouldn't you just buy a digital electric
pressure cooker in the first place? They're great.

