ATmega2560 Smart Room Monitor

A simple embedded monitoring system built on the ATmega2560 using AVR Assembly.

Overview

This project monitors environmental conditions in a small room or study-area model using three analog sensors:

• LM35 temperature sensor
• LDR light sensor
• KY-038 analog sound sensor

According to the detected conditions, the system activates different outputs:

• Red warning LED for high temperature
• Yellow warning LED for low light
• Green warning LED for sound events
• 5V cooling fan
• Active buzzer alarm

Project Objective

The objective of this project was to design and implement an embedded room-monitoring prototype using the ATmega2560 and AVR Assembly, integrating analog sensing and actuator control under predefined alarm conditions.

This work was developed as part of my Embedded Systems course project.

Main Features

• Reads three analog sensors through the ADC
• Controls LEDs, fan, and buzzer directly from the microcontroller
• Built almost entirely in AVR Assembly
• Works as a standalone embedded system without requiring a PC during operation

System Logic

Temperature

If temperature exceeds the configured threshold:

• Red LED turns on
• Fan turns on

Light

If the environment is dark:

• Yellow LED turns on

Sound

If a strong sound event is detected:

• Green LED turns on

To improve event visibility, the sound indicator now uses a short hold window:

• After a valid sound event, the green LED remains active briefly even if the next sample falls below threshold.

Alarm Conditions

• If three abnormal conditions are active at the same time, the buzzer sounds intermittently while active condition LEDs remain on
• If zero, one, or two abnormal conditions are active, the buzzer stays off

Hardware Used

• Arduino Mega 2560 / ATmega2560
• LM35
• LDR
• KY-038
• Active 5V buzzer
• 5V fan
• 2N2222 transistor
• 1N4007 diode
• LEDs
• Resistors
• Breadboard and jumper wires

ADC Channels

• A0 -> LM35
• A1 -> LDR
• A2 -> KY-038 analog output

Output Pins

• D12 -> Red temperature LED
• D11 -> Fan control
• D10 -> Yellow light warning LED
• D9 -> Green sound warning LED
• D8 -> Buzzer

Notes

• Presentation files are available in docs/.
• Build/reference photos are available in img/.
• The printable enclosure models are available in 3d/.
• The LDR was used as the sensor selected for the technical explanation of non-linear behavior.
• Threshold values were adjusted experimentally during testing.
• The sound sensor responds better to sharp nearby acoustic events than to continuous speech.
• Current firmware includes a short noise hold (HOLD_RUIDO) to avoid losing brief sound events between ADC cycles.