TSL2561 on OLED: Light Level (Broadband + IR)
Overview & Wiring
What it is: The TSL2561 is a light sensor with two photodiodes — one for visible+IR and one for IR only — so it can compute lux accurately across a huge range (0.1 to 40000 lux) and auto-range for both dim and bright scenes.
How it works: I2C device (default address 0x39). The Adafruit Unified Sensor library combines the two channels into a calibrated lux value and can auto-select gain and integration time. Shares SDA/SCL with the OLED.
Wiring (shared I2C bus with the OLED):
TSL2561 SDA -> GPIO4
TSL2561 SCL -> GPIO5
TSL2561 VCC -> 3V3
TSL2561 GND -> GND
OLED VCC=3V3, GND=GND, SDA=GPIO4, SCL=GPIO5
Libraries: "Adafruit TSL2561" and "Adafruit Unified Sensor" (installs "Adafruit BusIO"), plus "Adafruit SSD1306" and "Adafruit GFX Library".
On screen / Serial: light in lux. A reading of 0 in a very bright scene usually means saturation — auto-range handles most cases.
Gotchas: Address is 0x39 by default (0x29 if ADDR to GND, 0x49 if to VCC). Keep the plastic window clean; fingerprints skew the lux.
Circuit Diagram
Parts You Need
Source Code (Arduino / ESP32)
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_TSL2561_U.h>
Adafruit_SSD1306 display(128, 64, &Wire, -1);
Adafruit_TSL2561_Unified tsl = Adafruit_TSL2561_Unified(TSL2561_ADDR_FLOAT, 12345);
void setup() {
Serial.begin(115200);
Wire.begin(4, 5);
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
if (!tsl.begin()) {
Serial.println("TSL2561 not found");
display.setTextColor(SSD1306_WHITE);
display.setCursor(0, 28); display.println("TSL2561 not found");
display.display();
while (1) delay(10);
}
tsl.enableAutoRange(true);
tsl.setIntegrationTime(TSL2561_INTEGRATIONTIME_101MS);
}
void loop() {
sensors_event_t event;
tsl.getEvent(&event);
float lux = event.light; // 0 if overloaded
display.clearDisplay();
display.setTextColor(SSD1306_WHITE);
display.setTextSize(1);
display.setCursor(0, 0);
display.println("TSL2561 Light");
display.setTextSize(3);
display.setCursor(0, 22);
display.printf("%.0f", lux);
display.setTextSize(1);
display.setCursor(0, 54); display.print("lux");
display.display();
Serial.printf("Light: %.1f lux\n", lux);
delay(500);
}