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--- pm:prj2025:abirlica:macedoniu.pacuraru [2025/05/29 20:00]
macedoniu.pacuraru [Hardware Design]
+++ pm:prj2025:abirlica:macedoniu.pacuraru [2025/05/29 22:20] (current)
macedoniu.pacuraru [Bibliography/Resources]
@@ Line 33: / Line 33: @@
 {{:pm:prj2025:abirlica:schematicdefoc.png?500|}}
+Schematic made in Fusion 360. The ESP8266 was made manually because there seems to be no schematic for it on the internet.
 ===Connections Between Components===
@@ Line 44: / Line 46: @@
 - **Button (Reset Alarm)**
-  * One pin → pin D1 (GPIO5) of the ESP8266
+  * First pin → pin D1 (GPIO5) of the ESP8266
-  * Other pin → GND
+  * Second pin → 3.3V
-  * Software configuration: internal pull-up resistor is enabled with pinMode(D1, INPUT_PULLUP);
+  * Third pin → GND
-  * Purpose: Temporarily stops the alarm and resets the alert state.
+  * Software configuration: internal pull-up resistor is enabled with pinMode(D1, INPUT_PULLUP);
 - **Passive Buzzer**
   * Signal pin → pin D0 (GPIO16)
   * GND → GND
-  * Purpose: Emits a warning sound when the temperature exceeds the threshold. Controlled with tone() and noTone().
 - **SIM800L GSM Module**
@@ Line 59: / Line 60: @@
   * TX (SIM800L output) → pin D7 (ESP8266 RX)
   * RX (SIM800L input) → pin D8 (ESP8266 TX)
-  * Note: A voltage divider is recommended on ESP8266 TX → SIM800L RX, as the ESP outputs 3.3V and the SIM800L is sensitive.
   * VCC → separate 3.7V power source (Li-ion battery) or stabilized step-down converter
   * GND → Common GND with ESP8266
-  * Purpose: Sends a warning SMS only once for each alarm trigger.
+<note>
+  * Note: A voltage divider is recommended on ESP8266 TX → SIM800L RX, as the ESP outputs 3.3V and the SIM800L is sensitive.
+</note>
 - **ESP8266 (NodeMCU)**
   * USB → PC (for power and serial communication)
-  * Purpose: Acts as the system's control unit. It receives data from the sensor, decides whether to activate the alarm, and communicates via GSM.
 ===== Software Design =====
-The firmware is developed in the Arduino IDE targeting the ESP8266 platform. It follows these steps:
+The firmware is developed in the Arduino IDE targeting the ESP8266 platform.
+===Purpose of the Code===
+- **DHT11 Temperature Sensor**
+  * Reads the ambient temperature through digital pin D2 (GPIO4).
+  * If the temperature exceeds 26.1°C, an alarm state is triggered.
+  * The reading is done using the `Adafruit_Sensor`, `DHT`, and `DHT_U` libraries.
+  * Temperature is read periodically (every ~0.5 seconds) and logged to the serial monitor.
+- **Alarm System (Passive Buzzer and Button)**
+  * The buzzer is connected to pin D0 (GPIO16) and activated using the `tone()` function when an alarm is triggered.
+  * A push button connected to D1 (GPIO5) is configured with an internal pull-up resistor (`INPUT_PULLUP`).
+  * When the button is pressed, the alarm is silenced, and the system enters a cooldown period of 1 minute to prevent retriggering.
+  * `alarmActive` and `smsSent` boolean flags are used to manage system state.
+- **SIM800L GSM Module**
+  * Communicates with the ESP8266 via `SoftwareSerial` on pins D7 (RX) and D8 (TX).
+  * During setup, AT commands are used to initialize the module and verify signal/SIM status.
+  * Sends an SMS alert **once** per alarm event using the `sendSMS()` function.
+  * The SMS content is: *"ALERTA: Temperatura depaseste 26.1C!"*
+===Flow Overview===
+  * Upon startup:
+    - Serial communication is initialized.
+    - The DHT11 and SIM800L modules are set up.
+    - AT commands check SIM status, signal quality, and configure SMS mode.
+  * In the main loop:
+    - The system reads temperature from the DHT11 sensor.
+    - If temperature > 26.1°C and no alarm is active:
+      - The buzzer is activated.
+      - An SMS is sent (only once per event).
+    - If the user presses the button:
+      - The alarm stops.
+      - A 60-second cooldown prevents immediate retriggering.
+  * Messages and debug information are printed to the serial monitor for monitoring and troubleshooting.
+**Libraries Used**
+- `Adafruit_Sensor.h`, `DHT.h`, `DHT_U.h`: For interfacing with the DHT11 temperature sensor.
+- `SoftwareSerial.h`: Enables serial communication between the ESP8266 and the SIM800L GSM module.
-. Initialize the DHT11 sensor, buzzer pin, and UART communication with the SIM800L.
-. Enter a loop where temperature is read every two seconds.
-. If the temperature reading exceeds 50 °C, activate the buzzer and transmit an SMS alert via the GSM module using standard AT commands.
-. Otherwise, keep the buzzer silent and continue monitoring.
 ===== Results =====
+{{:pm:prj2025:abirlica:pozaresults.jpeg?500|}}
 ===== Conclusions =====
+Working on this project was both challenging and fun. At first, I wasn’t sure if everything would work together, especially the SIM800L module, which needed a lot of trial and error to set up properly. I also had to be careful with wiring and power, since I didn’t want to damage any components.
+I learned a lot about how to use interrupts, how UART communication works, and how to read data from the DHT11 sensor. I also got some practice debugging both hardware and software issues, which sometimes took a while but felt great once they were solved.
+In the end, I managed to build a system that detects high temperatures, triggers an alarm, and sends an SMS alert. It even has a button to silence the alarm, which works using interrupts.
+Even though it’s a simple version, I think it’s a good starting point, and I’m happy with how it turned out. With more time, I’d like to improve the design and maybe add more features. Overall, it was a great learning experience.
 ===== Bibliography/Resources =====
+[[https://newbiely.com/tutorials/esp8266/esp8266-dht11|ESP8266 with DHT11 – Newbiely guide]]
+– A detailed tutorial on how to connect and read temperature from a DHT11 sensor using the ESP8266.
+[[https://lastminuteengineers.com/sim800l-gsm-module-arduino-tutorial/|SIM800L GSM Module with Arduino – Last Minute Engineers]]
+– A complete guide for using the SIM800L module to send SMS messages via AT commands.
+[[https://arduino-esp8266.readthedocs.io/en/latest/reference.html|ESP8266 Interrupts – Official Documentation]]
+– Official Arduino documentation on using interrupts.
+[[https://www.theengineeringprojects.com/2020/09/lm2596-buck-converter-datasheet-pinout-features-applications.html|LM2596 datasheet and guide]]
+– Technical overview of the LM2596 buck converter module