I’m working on some stuff which will require distance sensing, so I’ve searched around and found that TCRT5000 sensors are very, very cheap. I’ve ordered some to test how they behave in practice.
The image above was what I’ve just found, and the recommended circuit for the sensor differs a bit to what I’ve found before. Luckily, the sensor seems to be Arduino-class resilient to abuse. :) Despite what the diagrams in the picture above show, and what the photo on the left seems to confirm, the package looks pretty much symmetrical to me, with the only visual difference between the two sides being the colour of the diodes. The black one is the receiver (transistor, T), and the bluish one the transmitter (diode, D).
My circuit looked something like this:
I.e. no external resistors (a pullup on the analog input), with an external LED connected to a PWM pin. The code simply turns on the TCR5000 diode, reads the analog input, and dims the external LED with PWM proportionally.
The TCR5000 module, I’ve learned later, is mostly used for “line tracking” in small wheel-mounted robots. There, it’s used simply to detect if the reflection changes, signifying that the course needs to change.
I’ve found that the sensor module is pretty good in detecting IR reflectivity, at around 10-20 cm. So, as an actual distance sensor it’s not very good, as it would basically need to be calibrated to every target surface type. It could be used as a simple on/off detector in simple applications.
