Line sensors (TCRT5000)

The test program

Test this part on its own before you build the rest: if it works alone, the rest is built on something you know works.

10 LED red, off
20 LED yellow, off
30 LED green, off
40 IF SENSOR("line-left")=1 THEN LED red, on
50 IF SENSOR("line-center")=1 THEN LED yellow, on
60 IF SENSOR("line-right")=1 THEN LED green, on
70 WAIT 100
80 GOTO 10

What you should see: Pass black tape under the sensors: on the left the red light comes on, in the middle the yellow, on the right the green.

What to buy

• 3 × Line sensor (TCRT5000)

How to wire it to an ESP32-S3

1. L → ESP32-S3: GPIO38
2. C → ESP32-S3: GPIO39
3. R → ESP32-S3: GPIO40
4. VCC → ESP32-S3: 3V3
5. GND → ESP32-S3: GNDCommon ground: this link is mandatory.

If it does not work

The program runs but nothing happens

The sensors are too far from the floor, or their screw is set wrong. Keep them a couple of centimetres above the floor and turn each one's screw until its LED changes between black and white.

What you can adjust

• The sensitivity of each sensor: the screw on the module.

Which boards it works on

• ESP32-S3 Freenove: yes
• Nordic nRF54LM20 DK: yes
• Arduino UNO R4 WiFi: yes