Chipkit Uno and GA1A12S202 light sensor example

In this example we will connect a GA1A12S202 Log-Scale Analog Light Sensor to a Chipkit Uno

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

Illuminance	Example
0.002 lux	Moonless clear night sky
0.2 lux	Design minimum for emergency lighting
0.27 – 1 lux	Full moon on a clear night
3.4 lux	twilight under a clear sky
50 lux	Family living room
80 lux	Hallway/toilet
100 lux	Very dark overcast day
300 – 500 lux	Sunrise or sunset on a clear day.
1,000 lux	Overcast day
10,000 – 25,000 lux	Full daylight
32,000 – 130,000 lux	Direct sunlight

 

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

Connection

Vcc – 3v
Gnd – Gnd
Out – A0

Code

 

[codesyntax lang=”cpp”]

int sensorPin = A0; //
float rawRange = 1023;
float logRange = 3.3;

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);
}

[/codesyntax]

 

Results

Open the Serial monitor and you should something like this

Raw = 198 – Lux = 4.35
Raw = 195 – Lux = 4.26
Raw = 181 – Lux = 3.84
Raw = 195 – Lux = 4.26
Raw = 9 – Lux = 1.07
Raw = 13 – Lux = 1.10
Raw = 186 – Lux = 3.98
Raw = 204 – Lux = 4.55
Raw = 195 – Lux = 4.26

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

Links

Adafruit GA1A12S202 Log-scale Analog Light Sensor [ADA1384]