VREL #1 and #3: General Purpose IoT Laboratory, air receiving nodes 1 and 3

The laboratory is located at Silesian University of Technology, Gliwice, Poland, Akademicka 16, room 310. There are two nodes of this kind: Node 1 and 3, one per two air ducts, constituting a pair of working devices along with Nodes 2 and 4 respectively.

The lab consists of a mechanical airflow indicator going from the pipe (connected to a neighbour, TX lab). The indicator is a vertical flap, which changes position depends on airflow. The position of the flap is observable, using the camera and measurable using a photoelectric proximity sensor. The signal from the sensor is sent to the AD converter and additionally is displayed on needle gauge.

The user needs to know:

• physical effect of the airflow,
• elementary rules od light propagation,
• work of the unbalanced bridge.

The sensor of flap position is made which photoresistors. For reference, next to the flap there is an immovable surface made with the same material like the flap. Like in case of flaps, here is an identical photoresistor. Both of resistor make an unbalanced bridge, with is balanced, if the flap is in the start position (without airflow). For balancing bridge in the start position, two another resistors in the bridge, are build which potentiometer.

The end of the air duct is fitted to a rectangle flap, The flap is hanging loosely and can be pushed by the airflow. The flap is lighted by LED form the top, and at the opposite side of the flap, there is the photoresistor, which measures light intensity, reflected from the flap. The flap sensing system is connected to the analogue input A0.

Independent, in the lab there is a sensor of temperature and humidity, DHT11, connected to the D4/GPIO2.

There are no mechanical actuators in this laboratory.
LCD Display is 4×20 characters. LCD is controlled via I2C extender: LCM1602. The I2C extender address is 0x3F and the I2C bus is connected to the pins D1/GPIO5 and D2/GPIO4 (D1 is SCL and D2 is SDA).
As you do not have any access to the serial console, use LCD to visually trace the progress of your program, connection status, etc. By the LCD display, there are two LEDs that can be used to trace status. One LED is connected to the pin GPIO 16 while the other one to the GPIO pin 2. The former one (GPIO 2) is connected to the Serial Port TX as well so expect it flashing when communicating over serial protocol (i.e. flashing new firmware that is beyond the control of your code).

LCD display requires a dedicated library. Of course, you can control it on the low-level programming, writing directly to the I2C registers, but we do suggest using a library first. As there are many universal libraries, and many of them are incompatible with this display, we strongly recommend using ''LiquidCrystal_I2C by Tony Kambourakis''. The LCD I2C control library can be imported to the source code via:

#include <LiquidCrystal_I2C.h>

Then configure your LCD controller:

LiquidCrystal_I2C lcd(0x3F,20,4);  // set the LCD address to 0x3F 
                                   // for a 20 chars and 4 line display

You can connect your ESP8266 microcontroller via its integrated WiFi interface to the separated IoT network. Then you can communicate with other nodes and players, already connected devices and even provide some information to the cloud. In details, there is a dedicated MQTT broker waiting for you. You can also set up your soft Access Point and connect another node directly to yours.

The communication among the devices can be done using MQTT messages, exchanging data among other nodes (M2M) and you can even push them to the Internet via MQTT broker.

Using your Node, you can access it and publish/subscribe to the messages once you connect your ESP to the existing wireless network (this network does not provide access to the global internet and is separated but please note there are other developers and IoT nodes connected to this access point:

• SSID: internal.IOT
• Passkey: IoTlab32768
• Setup your microcontroller for DHCP, to automatically obtain an IP address, your ESP will obtain the address from the 192.168.90.X pool.
• MQTT server is available under the fixed address: 192.168.90.5, and the credentials to publish/subscribe are:
  • User: vrel
  • Password: vrel2018

The same MQTT server/broker is visible under public IP: 157.158.56.54 port 1883 (non-secure) and 8883 (secure) to let you exchange data with the world and control your devices remotely.

At the same time, only one user can be programming the controller, although analysing the signal by others (unlimited number) the user has sense. Model is provided to work continuously, without service breaks. For more interesting experiments, the user should be access to complementary Tx lab at the same time.

In case the LCD display hangs and you are sure that your code should work but it does not, it may be the case the I2C bus is stuck and hang the I2C to LCD controller converter.
In this case, please use the following code to reset the I2C bus (you can embed it to your source code or run separately, then run your original code, again):

#include <Arduino.h>
#include <LiquidCrystal_I2C.h>
 
LiquidCrystal_I2C lcd(0x3F,20,4); 
 
void setup()
{
  pinMode(4,OUTPUT);
  pinMode(5, OUTPUT);
  digitalWrite(4,LOW);
  digitalWrite(5,LOW);
  delay(2000);
  pinMode(5, INPUT);       // reset pin
  pinMode(4, INPUT);
  delay(2050);
  lcd.init(D2,D1);
  lcd.backlight();
  lcd.home();
  lcd.print("Hello world...");
}
void loop()
{
 
}

Finally, you should see Hello World message on the LCD and I2C bus should be recovered now.