HeaterMeter v4.2 or v4.3
There are two active versions of HeaterMeter, v4.2 (aka 4.2.4) and v4.3 (aka 4.3.3, 4.3.4, 4.3.5, or 4.3.6). Both are equivalent in terms of functionality, their only difference is the form factor of the finished device. The largest difference is that v4.2 supports old (original) Raspberry Pi Model B and the v4.3 supports more modern Raspberry Pi.
- Raspberry Pi Model A or B (original), Raspberry Pi Zero / Zero W, or Raspberry Pi Model A+ (with modification)
- Wider, thinner form factor
- Dimensions: 127mm x 92mm x 29mm (339cm3)
- Single 4-way directional button
- Slightly cheaper due to single PCB design
- Raspberry Pi 3 Model B, 3A+, and 3B+, Raspberry Pi 2 Model B, Raspberry Pi Model B+, Raspberry Pi Model A+, Raspberry Pi Zero / Zero W
- Narrower, fatter form factor
- Dimensions: 100mm x 101mm x 36mm (363cm3)
- Four (4x) discrete buttons
- Slightly more expensive due to dual stacked PCB design
For the Raspberry Pi, if you have a MicroCenter store location near you, the cheapest solution is the Pi Zero W for a shockingly low $5. These can also be found online for about $15-20 shipped. They only have 2.4GHz wifi, so if you need wired Ethernet or 5GHz wifi, then the Raspberry Pi 3 B+ (2018) is what you want which runs at $35 (but usually over $40 shipped). The HeaterMeter experience on either is virtually indistinguishable.
I'd recommend the Zero W if you can get one and can live without wired Ethernet just because it saves a buncha money. If you get the Zero W, note that it doesn't include the pins needed to connect it to anything so you'll also need to pick up male header (0.1"/2.54mm pinheader, in 1x40 or 2x20 or 2x13 arrangement). I believe MicroCenter sells those and they're also up on the official store, or eBay has a thousand listings for them.
Note that there are many Raspberry Pi boards with the "B" model designation. Verify the model number (1, 2, 3, 4) and letter (B, B+)
- Raspberry Pi 1 B (original) - HeaterMeter 4.2
- Raspberry Pi 1 B+ - HeaterMeter 4.3
- Raspberry Pi 2 B - HeaterMeter 4.3
- Raspberry Pi 3 B (wifi) - HeaterMeter 4.3
- Raspberry Pi 3 B+ (2018 dual band wifi) - HeaterMeter 4.3
- Raspberry Pi 4 B (2019) - NOT SUPPORTED
There are also a few Raspberry Pi Zero boards
- Raspberry Pi Zero - HeaterMeter 4.3 requires external wifi adapter
- Raspberry Pi Zero W - HeaterMeter 4.3
- Raspberry Pi Zero WH - HeaterMeter 4.3
- Raspberry Pi Zero 2 W (2021) - NOT SUPPORTED
Not supported. This is actually not even the same sort of device the other Raspberry Pi are, it is strictly a microcontroller (like the ATmega) and not a full computer, which is what the Pi needs to be for a HeaterMeter.