Leah C Tech Stuff

 Today I am going to add a DHT22 temperature humidity sensor to my existing battery voltage monitor project. Uploading and testing the code is done over USB cable, the HC-05 needs to be disconnected for this to work. The DHT22 is connected to +5v, gnd and Digital Pin 10, I only chose pin10 as it is convenient for my veroboard layout. The code for this is very simple : <code> #include "DHT.h" #define DHTPIN 2 // The pin that your DHT is connected to DHT dht(DHTPIN, DHT22); void setup() { dht.begin(); } void loop(){ float h = dht.readHumidity();     //stores humidity value in float variable h float t = dht.readTemperature();// temperature value } </code> Don't forget to import the "DHT sensor library" in library manager in the Arduino IDE.  We can then do whatever we need to with the values. I am going to send request them over serial via a HC-05 Bluetooth device from a Python script on a Raspberry Pi.  For testing  am using a laptop running ...

 After getting a serial connection to work between an Arduino Nano and Pi Zero in a previous project I purchased a HC-05 Bluetooth module so that the Pi can be removed from the enclosure, this should reduce the power requirement significantly resulting in increased battery life. Power requirements : Pi Zero, Arduino Nano 290mA Arduino Nano, HC-05 module Bluetooth Module 50mA The power reduction is huge but it is a bid of a mess when soldered onto veroboard. (I have ordered a few ESP32 for a future improved version.) The wiring diagram is very similar, just replace the Pi Zero with the HC-05 as below. You can ignore everything to the right of the Nano, it is not required for Bluetooth but i am using it to retrieve a battery level reading. When powered up the led on the HC-05 should flash rapidly indicating ready to connect. To test you can use the Android app "Serial Bluetooth Terminal". The default pairing code is "1234". I will be using Python to communicate with t...