Color Sensor

Actually, LED in an inverted circuit can measure the intensity of light. In the case of an RGB LED, we can also measure the intensity within a given wavelength range.

A straightforward experimental configuration involves positioning two RBG LEDs in opposition, with one emitting and the other receiving, and using a simple operational amplifier circuit (with an approximate gain of x37) to support the concept.

We need :

• PLA printed bock
• 4 White Led (5mm diameter)
• 1 LED RBG (10 mm diameter)
• 2 Resistances 1MOhm
• 1 Resistance 5 MOhm
• 1 Resistance 330 Ohm
• Arduino Nano

This is only an estimate as the intensity emitted varies depending on the wavelength and so does reception. For the final assembly, separate amplifications can be used for each receiving wavelength or a single amplification can be used with differentiated current detection. It is particularly important to note that the color red has low amplification, requiring multiplication by five for effective detection.

The measurement is conducted by reflecting light from four white LEDs, all with a 5mm diameter. These LEDs are situated at the corners of a square PCB measuring 50mm².

The printed circuit board (PCB) plate is affixed to a black PLA block that centers the LED light within the system, thereby shielding the RGB LED from external lighting.

The sensor's sensitivity was tested on colored plastic covers at a constant gain and 5MOhm for the red color (diagram 2). Four different colors, including red, green, yellow, and blue, were selected. The output voltage responses varied depending on the color of the cover.