The ambient light sensor TEMT6000X01 from Vishay Semiconductors is sensitive to visible light much like the human eye. The measurement circuitry is configured to measure the illuminance from ~10 to ~900lx when the internal VCC/1.6 reference is used.
The data in Table 2 which shows the relationship between illuminance and output voltage of the sensor circuitry is generated based on the symbols and formulas shown in the table below.
| Symbols | Description |
|---|---|
| ICA | Calibrated sensor responsitivity at 100lx. This is 50μA according to the sensor datasheet. |
| Ev | Illuminance |
| I | Current through the sensor |
| U | Output voltage of the sensor circuitry that is provided to the ADC |
| R | Series resistor of the sensor circuitry. 4.7kΩ has been chosen in this design. |
| Ev = 100 × I / ICA | Illuminance is calculated based on the relation of the actual current through the sensor to the calibrated value at 100lx |
| I = U / R | Since the ADC measures the voltage across the series resistor of the sensor circuitry it is necessary to calculate the voltage based on the current |
| U = (Ev × R × ICA) / 100 | Based on the current and the illuminance the output voltage of the sensor circuitry can be calculated |
| Illuminance [lux] | ADC input [V] | Illuminance |
|---|---|---|
| 1 | 0.0024 | Dusk |
| 10 | 0.0235 | Dusk |
| 20 | 0.0470 | Dusk |
| 30 | 0.0705 | Dusk |
| 40 | 0.0940 | Dusk |
| 50 | 0.1175 | Living room |
| 60 | 0.1410 | Living room |
| 70 | 0.1645 | Living room |
| 80 | 0.1880 | Living room |
| 90 | 0.2115 | Living room |
| 100 | 0.2350 | Living room |
| 200 | 0.4700 | Office lighting |
| 300 | 0.7050 | Office lighting |
| 400 | 0.9400 | Office lighting |
| 500 | 1.1750 | Office lighting |
| 600 | 1.4100 | Office lighting |
| 700 | 1.6450 | Office lighting |
| 800 | 1.8800 | Office lighting |
| 900 | 2.1150 | Office lighting |
| 1000 | 2.3500 | Overcast day |