Spectral Measurement Platform

This is my Bachelorthesis: "Entwicklung und Realisierung eines Messsystems mit den Sensoren AS7261 und AS72651 von AMS"

The goal of this work is to develop a spectral sensor platform using the AS7261 and AS72651, which can be used modularly for different research purposes, but especially for sky measurements. Since it is not possible to measure in several directions in the sky at the same time with only one of the AS7261 (or AS72651) sensors without mechanical components, it must be ensured that a large number of sensors can be combined into a sensor array in order to be able to measure with directional resolution. The resulting sensor platform uses a Raspberry Pi 4 as central control unit, which communicates with external sensor boards via I2C.

The final sensor platform will be able to differentiate 21 spectral channels of incident light from up to 20 different directions.

Grafana WebInterface

Auto Gain

To increase the usable light intensity range, the AutoGain mode can be used.
Measurements are made in all 4 possible gains, the most accurate measured value is selected for each channel. This value is adjusted to the maximum gain with the function matchValueTo-MaxGain to allow a continuous representation of the output.

for (uint8_t gain_i = 0; gain_i < 4; ++gain_i){         // going through every gain
                settings(s[i].address, integrationValue, gain_i); // apply settings integrationValue is fix gain is 0-3
                MeasurementFromAdress(s[i].address);            // initiate measurement from current adress
                AS7261_measurement[gain_i] = getAS7261Measurement(s[i].address, measurement_time, gain_i, 1);    // get data and save to array
            }
            

Usage

Flash the SD image
Attach 1-20 Sensorboards in sereries
Connect to the Pi over SSH
start a detachable screen
make compiles and runs the software

ssh pi@[IP-ADRESSE]
git clone https://github.com/LennardBoediger/SpectralSensor
cd SpectralSensor
screen
make

Attatch the screen with screen -r
Follow the instructions to change the setting and start the measurement
The Webinterface can be found at port 3000 http://[RASPBERRY_PI-IP]:3000

Hardware

Sensorboard

I2C Lanes in Red.

Pi-Shield