/diy/ - Do It Yourself

>>1541121
The point is that there will be a small gap for the steam to get out, and since the steam has a finite viscosity there will be a small pressure drop between the inside and the outside as the hole in the lid basically acts like a resistor. I did the calculation with the Darcy–Weisbach (with a 4mm wide and 4mm deep hole) equation and it gave me a pressure drop of 84Pa if the boiling rate is 1L/5minutes (a very fast boil) and 0.55Pa for a boiling rate of 1L/12hours (probably a slow boil). This hole size would probably be too small for a rapid boil, so making it even tighter to get higher pressures is out of the question. Humidity sensors anywhere would probably lead to too much hysteresis.

A simple fan in a hole on the lid to measure the speed of the escaping steam would work fine, but having moving parts in the presence of liquid (especially something that needs cleaning) sounds like a bad idea. A pressure sensor can simply be gated behind a rubber membrane that will couple the pressure change without exposing the electronics to ingress.

I just now thought of this, but a rotameter like this image could be electronically encoded fairly easily if the floating piece itself were ferromagnetic, and a coil were placed at one end of the sensor, such that an increase or decrease in airflow would present itself as a change in inductance. The ball could easily be removed for cleaning, and would be easier than the rubber membrane to clean. The only problem is I doubt it would work in the case of an induction hob, but feeding some sort of control signal back into one of those beasts is probably beyond me anyhow. The idea is to build this (and a temperature sensor) into an electric frying pan so you can set the boil rate and forget about it. The thing would probably be controlled by an SCR or FET on full-wave rectified unfiltered mains, since that sounds easier than trying to control a TRIAC with an op-amp and what.