IoT-Based Smart Cradle with Cry Detection and Automatic Swinging

New parents often cannot stay beside a cradle all day, and a baby who wakes and cries may wait several minutes before anyone in another room hears and responds. Manual cradles need a hand to keep rocking, so a parent busy in the next room has no way to know the baby has woken until the crying grows loud. The IoT-Based Smart Cradle with Cry Detection and Automatic Swinging answers this with a small wooden cradle carrying a sound sensor, a servo motor and an ESP32 controller. When the sensor hears sustained crying, the controller starts the cradle swinging and sends an alert to a parent dashboard over Wi-Fi, so the baby is soothed while the parent is notified. The project is an academic prototype demonstrating sound sensing, threshold-based detection, servo motion control and IoT alerting in one build, made for demonstration and learning — it is not a medical device and never replaces adult supervision of an infant.

The smart cradle works as a short chain from sound to motion to alert. The KY-038 sound sensor, mounted at the head end of the cradle, converts room sound into an analogue voltage that the ESP32 reads every 500 ms (design target). The ESP32 compares each reading with the configured cry threshold of 65 dB (design target) and counts consecutive samples above it; only three in a row count as a cry, which separates sustained crying from a single loud noise. Once a cry is confirmed, the ESP32 drives the MG996R servo through a slow sweep that rocks the cradle, starts the auto-stop timer, sounds the buzzer and sends the cry event and live readings to the parent dashboard over Wi-Fi. The dashboard shows the sound graph, swing state, temperature, humidity and event log, and the parent can stop the swing or change its speed from the same screen.

1. The KY-038 sound sensor continuously measures the sound level near the cradle and sends an analogue signal to the ESP32.
2. The ESP32 samples the signal every 500 ms (design target) and compares each reading with the 65 dB cry threshold (design target).
3. When 3 consecutive samples stay above the threshold, the ESP32 confirms a cry; a single loud noise below 3 samples is ignored.
4. The ESP32 drives the MG996R servo motor through a slow sweep, rocking the cradle through its linkage arm, and starts the auto-stop timer.
5. The buzzer sounds a short alert and the 16x2 LCD updates to show the swinging state.
6. The ESP32 sends the cry event, live sound level, temperature and humidity to the parent dashboard over Wi-Fi.
7. The parent sees the alert on the dashboard, can stop the swing or change its speed, and the swing stops by itself when the timer ends.

Tech stack:

• ESP32-WROOM-32
• Arduino IDE
• KY-038 sound sensor module
• MG996R servo motor
• DHT11 temperature sensor
• HTML · CSS · JavaScript dashboard
• 16x2 LCD display
• 12 V power adapter

The smart cradle combines four capabilities that work together as one system. First, cry detection: a KY-038 sound sensor watches the sound level and flags a cry only when the level stays above a set threshold for three consecutive samples, so a single clap or door knock does not trigger it. Second, automatic swinging: an MG996R servo motor drives the cradle through a linkage arm as soon as a cry is confirmed, and stops by itself after a configurable timer. Third, the parent dashboard: the ESP32 sends live sound levels, swing status, room temperature and an event log to a web dashboard over Wi-Fi, so a parent in another room sees the alert immediately. Fourth, room monitoring: a DHT11 sensor reports temperature and humidity on the same dashboard, giving the parent one screen for the baby's surroundings.

• [Cry detection with 3-sample confirmation] The KY-038 sound sensor samples the sound level every 500 ms (design target), and the ESP32 flags a cry only after 3 consecutive samples above the 65 dB threshold (design target), so brief household noises do not start the swing.
• [Automatic swinging on cry] An MG996R servo motor drives the cradle through a metal linkage arm as soon as a cry is confirmed, with a configurable auto-stop timer (default 10 minutes, design target) and 5 speed levels set from the dashboard.
• [Parent dashboard over Wi-Fi] The ESP32 hosts a web dashboard showing the live sound-level graph, swing status, room temperature and humidity, and an event log of every cry and swing, viewable from any device on the same Wi-Fi network.
• [Room temperature and humidity display] A DHT11 sensor measures room temperature and humidity and shows them on the dashboard and on the 16x2 LCD, so the parent can check whether the room is comfortable.
• [Manual swing control] Swinging can also be started and stopped by hand from the dashboard or a push button, independent of cry detection, for testing and demonstration.
• [Local alert buzzer and LCD status] A buzzer sounds a short alert when a cry is detected and the 16x2 LCD shows the cradle state, so the system gives feedback even when no phone or dashboard is open.
• [Configurable thresholds] The cry threshold, sample count, swing speed and auto-stop time are all set in the firmware, so the student can tune the behaviour for the demo room and explain each setting in the viva.

• Working smart cradle prototype (wooden frame, ESP32, KY-038 sound sensor, MG996R servo, DHT11, LCD, buzzer)
• Complete firmware source code with configurable threshold, speed and timer settings
• Companion parent dashboard (single-file web app with live sound graph and event log)
• Circuit diagram and wiring documentation
• Component list with part numbers
• Project report PDF (background, methodology, architecture, results)
• Project abstract PDF
• PPT presentation for final review
• Viva Q&A preparation document