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.

Ohm Brew

My electronic home brew thermal controller is called the Ohm Brew. It is not online all the time, just when I am actually brewing.

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.

There is a bug with this plot. It first appears blank. The data will appear after a minute or so. I need to fix that.

Heat Pump Refrigerant

Temperature of refrigerant arriving at and leaving the indoor heat exchanger coil. I.e., 'supply' will be warm when heating the house and cold when chilling. 'Ambient' is ambient in the crawlspace near the furnace, not the duct temperature of air entering the heat exchanger.

Heat Pump Function

Duct air temperatures either side of the heat exchanger so you can see how much the heat pump is heating or cooling the air. Also shown are outdoor temperature and my dimentionless metric that is intended to identify at which of its three power levels the heat pump is running or if the natural gas furnace has kicked in instead.
Free01 is house air temperature, entering the heat exchanger.
Free04 is heated/cooled air in duct, leaving the heat exchanger.
Free02 is outdoors.
HP_stage is my dimentionless estimate of heat pump mode. Stage 1,2,3 on heat pump and 5 means gas furnace. I do not have a direct signal from the heat pump itself. This is purely my own cooked-up algorithmic estimate of which power level is currently running.

Humidifier Run Time

This plot shows the percentage of the time that the flow control valve is open on the humidifier so indirectly estimates the amount of water being used.

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'.

Radon monitor. Plot shorts short-term and long-term averages of the radon measurement. The grey line labeled "Inches H2O" shows the measured depressurisation below the radon membrane in units inches-of-water. Typcal value is around 1 and this purely serves to alert me if the extraction fan dies.
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

2022-04-24 4:03 PM