If you’ve lived in many apartments or houses, you have probably noticed that you end up setting your thermostat to different temperatures. A comfortable temperature in one home might be 72 degrees, while you might need to crank it down to 68 degrees in another home. That is partially because of thermometer inaccuracies in the thermostats, but is more heavily influenced by where the thermostat is placed. If you have a two-story house, for example, the second floor will be significantly hotter than the first floor. That’s why ValentinJ2 built these cheap ESP8266-based temperature and humidity sensors that can be dispersed throughout his home.
ValentinJ2 felt like some rooms in his home were colder than others and wanted a way to check in order to find out for sure. The devices he designed can measure both temperature and humidity throughout the day and can be plugged right into a USB charger in any outlet. They let him collect data 24/7, which he can then compare to see when specific rooms vary in temperature and by how much. That, in turn, can help him set his thermostat appropriately and could even yield valuable information about where insulation can be added or if his HVAC system needs work or adjustment. ValentinJ2 has also provided instructions on how to build these devices yourself, so you can monitor your own home.
Each device is based on an ESP8266 microcontroller, which was chosen because it is affordable and has built-in WiFi. That ESP8266 is soldered onto a custom PCB with a DHT22 temperature and humidity sensor. Power comes through a USB-A male connector and then goes to the ESP8266 via a 3.3V LD1117V33 voltage regulator. The only other components are a couple of capacitors, a resistor, and some female headers. ValentinJ2 is using a couple of pieces of acrylic with stand-offs to protect the PCB, but you could 3D-print an enclosure or leave the PCB exposed. The provided codes lets each ESP8266 connect to your WiFi network and will send the collected data to the Blynk service. Blynk provides a handy smartphone app that you can use to check the data. That makes it really easy to compare the temperature and humidity in each room in order to determine your home’s average temperature and which rooms are chilly or hot.