1 Technophile

I have built an external sensor so as to monitor temperature, air humidity, soil humidity of my garden and the battery voltage. The requirements was: waterproof long battery life, the atmega328p run at 8mhz with minimal components and functions under 10€ wireless (433Mhz) with good range (2 walls to cross and 10 meters) Here is the final view: And some reports from OpenHab displaying the sensor data: Air humidity Soil humidity Air temperature We can of course imagine to use these values to control a water pump. Now let's see hpw to build this. Bill of material The sensors is based on atmega328p (3€),  a 433 Mhz transmitter (1,5€) , a DHT11 (1€) or a DHT22 temperature and humidity sensor, a soil moisture sensor  (1,6€), an electrical box (1€)  a 433 mhz antenna (0,18€) DIP socket adaptor for the ATmega (1€) an electronic prototype printed circuit board (0,5€) a recycled  tube At total we are around 10€ ...