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Automated Pet Feeder with ESP32, a Servo, and an RTC Module
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Traveling for a few days while worrying whether your cat or dog is getting fed on time is a familiar kind of anxiety. This automated feeder uses a servo to rotate a food-dispensing wheel, a DS3231 RTC module to keep accurate time even without WiFi, and a small web server running right on the ESP32 so you can tap “feed now” from your phone.
How it works
- The ESP32 checks the current time from a DS3231 RTC module (independent of any Internet/NTP connection, since the RTC has its own coin-cell battery to keep time through power loss).
- At each scheduled time (say, 7am and 6pm), the ESP32 drives the servo through a fixed angle to open the dispensing wheel, dropping one portion of food into the bowl.
- Alongside that, the ESP32 runs a small web server with a
/feed-nowendpoint — just open a phone browser to the ESP32’s IP address and tap the button to trigger an extra feeding immediately.
Parts list
- ESP32 DevKit
- SG90 or MG90S servo (MG90S holds up better if the dispensing wheel carries a heavier load)
- DS3231 RTC module (far more accurate than a DS1307, with built-in temperature compensation)
- A food hopper (3D-printed, or repurposed from a cut plastic bottle/container) connected to a notched dispensing wheel that scoops a portion of food per rotation
- A stable 5V supply for the servo (avoid sharing the ESP32’s 5V pin if the servo causes a startup surge; a 470-1000µF buffer capacitor can help if needed)
Sample code
#include <WiFi.h>
#include <WebServer.h>
#include <ESP32Servo.h>
#include <Wire.h>
#include <RTClib.h>
const char* WIFI_SSID = "your-wifi-name";
const char* WIFI_PASS = "your-wifi-password";
Servo feederServo;
RTC_DS3231 rtc;
WebServer server(80);
const int SERVO_PIN = 18;
const int FEED_HOURS[] = {7, 18}; // 7am and 6pm
const int FEED_MINUTE = 0;
int lastFedDay[2] = {-1, -1}; // tracks the day already fed to avoid double-triggering within the same minute
void rotateFeederServo() {
feederServo.write(90); // open position, rotating 90 degrees
delay(700); // enough time for the wheel to rotate and drop food
feederServo.write(0); // back to closed position
Serial.println("Fed!");
}
void handleFeedNow() {
rotateFeederServo();
server.send(200, "text/plain", "Fed on demand!");
}
void handleRoot() {
DateTime now = rtc.now();
String html = "<html><body style='font-family:sans-serif'>";
html += "<h2>Automated Pet Feeder</h2>";
html += "<p>Current time: " + String(now.hour()) + ":" + String(now.minute()) + "</p>";
html += "<button onclick=\"fetch('/feed-now')\">Feed now</button>";
html += "</body></html>";
server.send(200, "text/html", html);
}
void setup() {
Serial.begin(115200);
feederServo.attach(SERVO_PIN);
feederServo.write(0);
Wire.begin();
if (!rtc.begin()) {
Serial.println("Could not find RTC module!");
}
WiFi.begin(WIFI_SSID, WIFI_PASS);
while (WiFi.status() != WL_CONNECTED) {
delay(300);
Serial.print(".");
}
Serial.println("\nIP address: " + WiFi.localIP().toString());
server.on("/", handleRoot);
server.on("/feed-now", handleFeedNow);
server.begin();
}
void loop() {
server.handleClient();
DateTime now = rtc.now();
for (int i = 0; i < 2; i++) {
if (now.hour() == FEED_HOURS[i] && now.minute() == FEED_MINUTE && lastFedDay[i] != now.day()) {
rotateFeederServo();
lastFedDay[i] = now.day(); // mark today as fed for this slot, prevents repeating
}
}
delay(1000); // checking once a second is plenty, no need to poll continuously
}The servo angle (90 degrees in the example) and hold time (700ms) both need tuning to your specific dispensing wheel design — 3D-print a few wheel variants with different notch sizes to find the portion size you actually want per rotation.
Common pitfalls
- Using NTP/WiFi for timekeeping instead of the RTC sounds simpler but leaves the feeder completely lost on time if the router happens to reboot at the wrong moment — a DS3231 with its own CR2032 battery keeps accurate time through power loss or dropped WiFi.
- Sharing servo power with the ESP32 can cause a voltage sag when the servo starts moving, resetting the board — use a separate 5V supply with a shared ground between the two.
- Skipping duplicate-feed protection: without tracking
lastFedDay, the servo can trigger repeatedly within the same minute since the loop runs far faster than 60 seconds. - An open hopper absorbs moisture, clumping the food and jamming the wheel — use a sealed lid and store it somewhere dry.
Where to go from here
Add a weight sensor under the food bowl to confirm the pet actually ate (not just that food landed in the bowl), or attach an ESP32-CAM to snap a confirmation photo of every feeding and push it through a messaging app.
Tags:#esp32#servo#automation
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