1. Automatic Night Light

Increase LED brightness as the room gets darker, or switch to a remotely controlled manual mode. This combines a local sensor and a cloud command in one predictable behavior.

Level: Intermediate · Time: 40 minutes

Parts and wiring

ESP32, LDR, 10 kΩ resistor, LED, and 220–330 Ω resistor

Part	ESP32 connection
LDR measurement	`3V3 → LDR → GPIO34 → 10 kΩ → GND`
LED anode	GPIO 23 through 220–330 Ω
LED cathode	GND

PxServ keys

Key	Value
`night-light/mode`	`automatic` or `manual`
`night-light/manual-brightness`	`0–100`
`night-light/light`	Measured percentage
`night-light/brightness`	Applied percentage

Complete sketch


#include <PxServ.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 LDR_PIN = 34;
const int LED_PIN = 23;
 
PxServ client(PXSERV_API_KEY);
String mode = "automatic";
int manualBrightness = 0;
unsigned long lastCommandAt = 0;
unsigned long lastTelemetryAt = 0;
 
void readCommands() {
  PxServ::Callback modeResult = client.getData("night-light/mode");
  if (modeResult.status == 200) mode = modeResult.data;
 
  PxServ::Callback brightnessResult = client.getData(
    "night-light/manual-brightness"
  );
  if (brightnessResult.status == 200) {
    manualBrightness = constrain(brightnessResult.data.toInt(), 0, 100);
  }
}
 
void setup() {
  Serial.begin(115200);
  pinMode(LED_PIN, OUTPUT);
  analogReadResolution(12);
  PxServ::connectWifi(WIFI_SSID, WIFI_PASSWORD);
}
 
void loop() {
  unsigned long now = millis();
  if (now - lastCommandAt >= 3000) {
    lastCommandAt = now;
    readCommands();
  }
 
  int rawLight = analogRead(LDR_PIN);
  int lightPercent = constrain(map(rawLight, 0, 4095, 0, 100), 0, 100);
  int brightness = mode == "manual" ? manualBrightness : 100 - lightPercent;
  brightness = constrain(brightness, 0, 100);
  analogWrite(LED_PIN, map(brightness, 0, 100, 0, 255));
 
  if (now - lastTelemetryAt >= 10000) {
    lastTelemetryAt = now;
    client.setData("night-light/light", String(lightPercent));
    client.setData("night-light/brightness", String(brightness));
    client.setData("night-light/active-mode", mode);
  }
  delay(20);
}

Test

Cover the LDR in automatic mode, then set manual mode and brightness 25. A value outside 0–100 is safely constrained. If automatic behavior is reversed, swap the divider direction or remove 100 - from the calculation.