2022-07-21

Why buy a $10 thermometer when you can spend $100 and build one yourself in 15-20 hours?

Caitlin kept saying the thermostat was off so I build this to find out. As a bonus, it also tells me my house is too humid so now I have to also figure that out. Fun.

I was stubborn and wanted to use an attiny85 regardless of whether it was a good idea or not. 5 pins isn’t enough to control the display so I used a shift register as an IO expander to talk to the 1602 led display using SPI.

The temp/humidity sensor originally was an aht11 but apparently that unit is extremely sensitive to timing and I couldn’t quite get it right with the attiny. I switched to an AM2301B and that used i2c for communication and worked really well.

First try I soldered everything backwards but I eventually got it right.

The packing took forever and I ended up having to buy multiple project boxes to get the right size.

All done!