ESP32 and GA1A12S202 light sensor example

In this example we will connect a GA1A12S202 Log-Scale Analog Light Sensor to an ESP32 LOLIN32 module from Wemos.

The features of this sensor are as follows

Output voltage increases with light on the sensor
Logarithmic response not only gives more sensitivity in low light, its also almost impossible to “max-out” the sensor
Dynamic range of 3 to 55,000 Lux
Use indoors and outdoors without needing to recalibrate

Again these are typically best used in breakout/module form. Here is a picture of the module

GA1A12S202

Parts Required

Here are the parts I used

Name	Link
ESP32		Aliexpress link Amazon Ebay
GA1A12S202		Ebay link
Connecting cables		Aliexpress link Amazon Ebay

Connection

Vcc – 3v
Gnd – Gnd
Out – 36

LOLIN32 and GA1A12S202

Code

int sensorPin = 36; //
float rawRange = 4096;
float logRange = 5.0;

void setup()
{
Serial.begin(9600);
}

void loop()
{
// read the raw value from the sensor:
int rawValue = analogRead(sensorPin);

Serial.print("Raw = ");
Serial.print(rawValue);
Serial.print(" - Lux = ");
Serial.println(RawToLux(rawValue));
delay(1000);
}

float RawToLux(int raw)
{
float logLux = raw * logRange / rawRange;
return pow(10, logLux);
}

Results

Open the Serial monitor and you should something like this

Raw = 1235 – Lux = 32.18
Raw = 1227 – Lux = 31.46
Raw = 192 – Lux = 1.72
Raw = 26 – Lux = 1.08
Raw = 1216 – Lux = 30.51
Raw = 720 – Lux = 7.57
Raw = 2001 – Lux = 277.09
Raw = 1759 – Lux = 140.35
Raw = 1259 – Lux = 34.42

The sensor was covered and moved close to a desktop lamp – the higher values