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--- pm:prj2025:iotelea:alexa_andreea.voicu [2025/05/26 00:21]
alexa_andreea.voicu [Component list]
+++ pm:prj2025:iotelea:alexa_andreea.voicu [2025/05/26 21:44] (current)
alexa_andreea.voicu [Software Design]
@@ Line 41: / Line 41: @@
 The LCD display shows live values of temperature and humidity and the alerts for the user, while LEDs indicate status:
-Green = optimal
-Yellow = warning
+  * Green = optimal
+  * Yellow = warning
-Red = out of range
+  * Red = out of range
 The buzzer notifies the user when human intervention is needed.
@@ Line 124: / Line 123: @@
 ===== Software Design =====
-The Arduino sketch uses the following libraries:
+=== Libraries ===
+The program was developed using the Arduino IDE, and relies on several key libraries for sensor communication, display control, data logging, and peripheral management:
-DHT sensor library
+DHT.h – for reading temperature and humidity values from the DHT22 sensor
-Adafruit SSD1306 (for OLED)
+Wire.h & LiquidCrystal_I2C.h – for controlling the I2C 1602 LCD display
-SD library
+SD.h – for writing environmental data to the microSD card
-Wire (I2C communication)
+tone() – native Arduino function used to control the passive buzzer with PWM audio signals
-Functional logic:
-Read DHT22 values every 2 seconds
+=== The flow ===
-Log data to SD every 60 seconds
+In each cycle it performs the following tasks:
-Compare values against threshold:
+Read data from the DHT22 sensor
-If temp < 37°C → turn ON heat
+Evaluate both temperature and humidity and assign status flags:
-If humidity < 50% → turn ON humidifier
+= optimal (green)
-If values are too low/high → buzzer + red LED
+= medium (yellow)
-If values are optimal → green LED
+= critical (red)
+Determine the worst case (maximum of the two flags) to define the overall system status
-===== Probleme întâmpinate =====
+Temperature and humidity evaluation:
+If temperature or humidity drops below/above certain thresholds, the corresponding flag is set to red (2).
+If values are within an acceptable but not ideal range, yellow (1) is assigned.
+Ideal values result in green (0).
+The worst of the two flags determines the LED status and whether a buzzer or fan should be activated and displays the message accordingly.
+The buzzer is passive, meaning it needs a signal with a defined frequency.
+It only activates when the system transitions into the red alert state
+It emits three tones with decreasing frequency (1000 Hz → 800 Hz → 600 Hz), each followed by a short pause.
+Total alert duration is approx. 2 seconds.
+The tone is played using Arduino’s tone() function and not repeated unless a new red alert is triggered.
+The fan is connected via an IRF520 module and is triggered only if the temperature exceeds 27°C.
+It automatically shuts off once the temperature returns to the safe range.
+The I2C LCD shows:
+Alerts, "Low/High temperature!", "Low/High humidity!" when entering critical states
+Live readings, Temp: ... C, Hum: ..% when values are stable
+Logging confirmation, "Logging data..." when writing to SD
+Priority is given to alert messages, which override live readings for 2 seconds
+===== Rezultate obținute =====
+The project was successfully implemented and tested and all major functionalities work as intended.
+Demo:
+[[https://www.youtube.com/shorts/_8tk-wFxubc|Smart Egg Incubator]]
 ===== Concluzii =====
+While my project wasn’t very complex, it gave me the opportunity to integrate multiple hardware components and manage real-time system logic. The availability of the libraries for the DHT22 sensor, LCD, and SD card modules helped me a lot with my work, allowing me to focus more on logic and the incubator's behavior.
-===== Resurse =====
+The biggest challenge was controlling the fan. I initially underestimated the current it needed, and quickly realized that driving it directly from a digital pin was not possible. So I needed to used a 12V battery, but wasn't sure how i would actually connect it so that it would work without any risks. After some research, I added an IRF520 Mosfet module, and thinking now, a flyback diode would have been a great addition to protect against voltage spikes when switching off the fan.
+Another issue was that I didn't know what the timing conflicts would be between SD card access and LCD updates. At one point, I
+was trying to write to the SD card while displaying messages caused flickering and delays. I had to be careful about when and how often updates happened, and add short delays to give each module time to operate without interfering.
+Overall, the project helped me learn how to integrate sensors, fans and storage, and how to troubleshoot the small issues that appear only when everything is running at the same time.
+===== Resurse =====
+  * [[https://www.arduino.cc/reference/en/|Arduino Official Documentation]] – language reference and built-in functions
+  * [[https://github.com/adafruit/DHT-sensor-library|DHT Sensor Library by Adafruit]] – for reading temperature and humidity values
+  * [[https://github.com/johnrickman/LiquidCrystal_I2C|LiquidCrystal I2C Library]] – used to control the 1602 I2C LCD display
+  * [[https://www.arduino.cc/en/Reference/SD|Arduino SD Library]] – for reading/writing data to the microSD card
+  * [[https://www.arduino.cc/reference/en/language/functions/advanced-io/tone/|tone() – Arduino Function]] – used to generate PWM audio signals for passive buzzers
+  * [[https://cdn-shop.adafruit.com/datasheets/Digital+humidity+and+temperature+sensor+AM2302.pdf|DHT22 Datasheet]] – for technical specifications of the sensor
+  * [[https://www.youtube.com/watch?v=17vqLv508Uw|Using IRF520 Mosfet]] – for connection to the fan