I needed a filament dryer so after checking various reviews, notably the one from My Tech Fun, I bought a refurbished (with warranty) Gratkit Firefly V2, which costs just 35 Euro plus shipment.
The dryer works really well and it has a (quiet) fan to circulate the air inside for uniform heating. It also has WiFi connectivity so that Tuya app can be used to control it.
For completeness, it doesn’t really support 72 mm spools as stated, but only 70 mm.
In my case the Tuya app was not useful, but I could connect it to Home Assistant using a specific custom integration (not all Tuya integrations work with it). This allows me to read and control various parameters locally, without the need for the cloud (not all of them work).
The interesting ones are humidity and temperature, which can be used to monitor the point where the humidity stops decreasing, indicating that the filament is mostly dry. If desired, an automation could be used to stop the dryer and save power.
I also wanted to monitor the power consumption, so I connected the dryer via a smart plug SP111 with energy monitoring, flashed with ESPhome. It performs power measurements at 10 seconds intervals.
I was then surprised to notice that the power consumption was in the range of 80 W, not 48 W as per official rating, see graph and power adapter:
This is a combined graph with power consumption and internal temperatures:
The 1 minute average shows that after the initial 10 minutes at almost twice the rated power, the averages return more or less within specifications, which is likely why the power adaptor is still functioning.
The heater element probably was indeed rated at about 50 W in the first revision, which was therefore unable to reach the nominal 70 °C temperature. In the second revision they must have updated the heater element, without updating the power supply. I wonder how the power consumption would look like if I connected a 24 V power supply actually rated at 96 W (4 A).
As a bonus graph, the plot of fan speed and internal temperature:
