The fridge

This page now has little to do with our fridge. The title refers to the fact that when I started playing with power monitoring I used our fridge as the test case. What follows is acually a disorganized assortment of environmental and power monitoring. These plots are mainly tests and experiments for my own entertainment. There is nothing here that is likely to enthrall you.

Coffee machine

I remember when I was working in Cambridge back in early 90s being amazed by the Trojan Room Coffee Pot. The idea of hooking up devices that were not themselves computer workstations to the internet seemed radical and exciting. It was the first time I got a hint that the internet might be more than an academic data distribution, communication and research tool. In honour of the Trojan Room Coffee Pot which was afterall an inspiration to virtually everything else on these pages, and twenty years after that went online, here's the current temperature of the boiler on my coffee machine at home.

Just like the Trojan Room Coffee Pot often was, offline until I replace the network card in the coffee machine.


Test runs for calibration of electronic hydrometer.

Gravity test plot

Display up to 1 hour of real time scrolling data.

Power (Watts)

The system is still in testing so, what is being logged to each channel can change. As of writing this I have the house air circulation fan, the fridge and a combined total for one side of the supply.

Circulation fan


Half of total supply

Two DS18B20 thermometers. They tend to move around a bit depending what I am playing with. They have been in the fridge, the freezer and Kimberly's closet, but at time of writing (Dec 2015) are one each in the garage and the 'brew cupboard'.

Six AM2302 electronic hygrometers in my prototype calibration vessel. These devices are factory calibrated with no easy way for the user to modify the internal calibration. We can however compare the factory calbrations to see how consistent they are and apply a rescaling in software to fine tune the output numbers if we wish. First impressions are that though there are measurable differences, these extremely cheap devices are impressively linear and consistent for the price. (An incomplete write-up of this experiment.)

Prototype radon monitor. Not stable. Expect this to come and go as it gets tinkered with.
See also: Monitoring household radon to test the efficacy of our home radon mitigation.


Longer term historical data (up to 1 year) but not updating in real time. Comparing two different kinds of sensor attached to the same power feed.


Mains Voltage RMS

2017-02-24 11:43 PM