diff --git a/README.md b/README.md
index bb87121..e843155 100644
--- a/README.md
+++ b/README.md
@@ -7,3 +7,6 @@ The measured parameters are sent to the ZeroIoT server once per minute.
 ### List of components
 * ESP8266 WeMos D1 mini board
 * DHT21 temperature and humidity sensor (AM2301)
+
+### Breadboard circuit diagram
+![circuit](/img/air_state_sensor.png)
diff --git a/air_state.ino b/air_state.ino
index c253b14..c6fd5c1 100644
--- a/air_state.ino
+++ b/air_state.ino
@@ -11,14 +11,15 @@
 #include <ESP8266HTTPClient.h>
 #include <DHT.h>
 
+// WiFi settings.
 const char* ssid   = "****";
 const char* passwd = "****";
 String iot_server_url = "http://your_zeroiot_server_address:3000/air_state"; // zeroiot
 String device_id = "esp8266_wemos_2";
 String location = "kitchen";
 
-#define DHTTYPE DHT21 
-DHT dht(D2, DHTTYPE);
+// Sensor settings.
+DHT dht(D2, DHT21);
 
 // For proper working section for avoiding data contamination
 // I need remember previous measurement results.
diff --git a/img/air_state_sensor.png b/img/air_state_sensor.png
new file mode 100644
index 0000000..6d5b6a1
Binary files /dev/null and b/img/air_state_sensor.png differ