Home Assistant and ESPHome are awesome - Smartifying my chest freezer

Problem
I had a chest freezer that went out a couple weeks ago, it was 5 years old. These things are very cheap, many less than $300, but of course the food loss was more than that. They hold temp pretty well without power or while broken, so I have no idea how long it was busted before we realized things were thawing out.

Freezer alarms are cheap and easy, but also basic, and I wanted something that I could tie into other systems. I also thought that I could detect earlier signs of failure than just monitoring temperature.


Solution
NodeMCU, a couple of sensors, a breadboard (for now), ESPHome, and Home Assistant. I'm not a pro with all this stuff, but I have fiddled with most of it enough that it was all pretty easy. I already had a current transformer on hand, but it outputs a current signal instead of voltage so I had to add a burden resistor. It's also 100amp, so if I were ordering new for this project I would have chosen a different one. However, even though the freezer only draws 1.5 amps, I'm getting pretty good resolution and consistent readings out of this CT.

ESPHome is really easy to use. It's not even programming really, you just write config files and ESPHome generates and flashes the code for you. You can even update it over the air, so once installed you don't have to keep hooking your device up to a computer to make changes. It also integrates really nicely with Home Assistant.


Results so far
I'm getting good readings on freezer temp and current draw. I don't know how accurate the temp probe is in this temp range, nor do I know how accurate the current readings are (I just calibrated it to the freezer nameplate data), but I'm not so much interested in absolute accuracy as I am in how these values change over time.

Temperature over time:



As you can maybe tell, it was working well for most of the night, but then I started fiddling this morning and my quick and dirty wiring came loose. Did a little bit more solid job (though still dirty) and readings are stable again.

Current draw:



You can clearly see when the unit was cooling and when it was not, as well as the big current spikes when the compressor first starts up. I have it taking readings every second, which is far more than I need, so I'll probably turn that down to every few seconds or a minute or something.

Anyway, it runs far more often than I was expecting, but I don't know if that's because it's mostly empty right now, or because I've been opening it a lot, or if my expectations were just wrong. It's running about 2/3 of the time, and at 1.5 amps that's nearly 3 kwh per day, which will cost about $10/month. I was hoping for half that. I will see how it goes as it fills up and I stop messing with it. My calibration could also be wrong and it may be drawing more or less than what is listed on the nameplate, so I will calibrate to a known load when I get a chance.

Basic dashboard card:




Going forward
I definitely need to clean up all the wiring and print an enclosure, but the point of all this was to make it useful. To do that, I will have to write some HA automations to let me know when these values start creeping out of line. My hope is that should this thing start to fail in a few years, I will be able to detect it well ahead of time to save the contents. I can't be sure just yet, but I would think that the runtimes would start creeping up days/weeks leading up to failure. I can also add a second temp probe to monitor the compressor temp, as well as a lid open/close sensor to alert when the kids leave it open after grabbing a popsicle.


Cost
NodeMCU $4
Current transformer $8
Temp probe $2.50
3.5mm stereo jack $0.75
Power adapter $10
Breadboard, misc wiring & components ~$1
3d printed enclosure (future) ~$1

Total BOM $27.25

Keep in mind these are Amazon retail prices, and the costs could easily be cut in half by ordering from overseas.



I'll be busy this afternoon, but maybe tomorrow or over the weekend I will post some photos, diagrams, and/or code if anyone is interested.