6. Remote Servo Lock

Read locked or open from PxServ and move an SG90 servo between two defined angles. Requested and applied states remain separate.

Level: Intermediate · Time: 40 minutes

Power and wiring

ESP32, SG90 micro servo, ESP32Servo library
Stable external 5 V servo supply

Servo	Connection
Signal	GPIO 18
VCC	External 5 V
GND	External-supply and ESP32 GND shared

Never power the servo from ESP32 3V3. This is a desktop mechanism prototype, not a security-rated lock.

Complete sketch


#include <PxServ.h>
#include <ESP32Servo.h>
 
const char* WIFI_SSID = "your_wifi_ssid";
const char* WIFI_PASSWORD = "your_wifi_password";
const char* PXSERV_API_KEY = "your_pxserv_api_key";
const int SERVO_PIN = 18;
const int LOCKED_ANGLE = 15;
const int OPEN_ANGLE = 95;
 
PxServ client(PXSERV_API_KEY);
Servo lockServo;
String appliedState = "";
 
void applyState(String state) {
  if (state == "open") {
    lockServo.write(OPEN_ANGLE);
    appliedState = "open";
  } else {
    lockServo.write(LOCKED_ANGLE);
    appliedState = "locked";
  }
  delay(500);
  client.setData("servo-lock/status", appliedState);
}
 
void setup() {
  Serial.begin(115200);
  lockServo.setPeriodHertz(50);
  lockServo.attach(SERVO_PIN, 500, 2400);
  lockServo.write(LOCKED_ANGLE);
  appliedState = "locked";
  delay(500);
  PxServ::connectWifi(WIFI_SSID, WIFI_PASSWORD);
  client.setData("servo-lock/status", "locked");
}
 
void loop() {
  PxServ::Callback command = client.getData("servo-lock/command");
  if (command.status == 200 && command.data != appliedState) {
    applyState(command.data == "open" ? "open" : "locked");
  }
  delay(2000);
}

Test and production note

Test angles before attaching the horn to the mechanism. Reduce them if the servo stalls. The reported status confirms the target command was written, not the physical position; add a limit switch for verified locking.