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© 2017 Ian Watts

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Milk Saver

... safeguarding my coffee (and the pan)...

Like I say, I like my coffee and things never turned out too great when I needed to heat my milk in a saucepan !

In the end, I made this 'Milk Saver'. VERY simple : a battery (CR2032) a buzzer, a thermistor, a 1K variable pot, some bits of wire and a mechanical thermometer from Amazon (£2.99).

The whole thing took less than a day to complete and has been REALLY effective.

I tried out the idea on a breadboard / veroboard first - just to get the right value pot and make sure the idea worked.

The pot / variable resistor is there to enable the correct temperature to be set. To be fair, once the circuit is set up to howl at the right temperature, the pot could be swapped out for a fixed-value resistor. I never did, I simply designed the pot into the plastic enclosure.

There is no On/Off switch and the CR2032 lasts around 5 months before needing replacing. I have a new / upgraded design in the pipeline that uses an smd AVR as the 'brain', 2xLR44 batteries (much smaller / better form factor) and a 'tilt' switch to wake the AVR for a pre-defined (5 minute) period. This approach (on veroboard at the moment has the benefit of extending battery life to, so far, more that 12 months and enables switching out the flat-panel enclosure for a smaller, in-line, tubular enclosure that doesn't hang over the edge of the pan and heat up...

In this image, the buzzer can the clearly seen. The pot is located at the opposite end. The plastics are PLA (non-hazardous but melts at a lower temperature that ABS).

The thermistor is connected to 80mm of wire and sits at the bottom end of the stainless stell tube / spike which is placed in the milk. The whole thing is kept in place on the saucepan by the spring clip that came with the original mechanical gauge.

The mk1 design :

The new, redesigned, mk2 unit SHOULD be much neater (and not get so hot when I carelessly place it over the gas burner ! )  but I now need to finish it off !! Which is hard to find the time to do - given that the current version works so well !