It all depends of what you are trying to detect and the particular application/environment.
The HC504 is an ultrasonic emiter/receiver perfect for detecting distance to a facing object. There are many other sensors, even combined ones that allow you to detect color and even sense of direction of the detected object...
It all depends of what you are trying to detect and the particular application/environment.
The HC504 is an ultrasonic emiter/receiver perfect for detecting distance to a facing object. There are many other sensors, even combined ones that allow you to detect color and even sense of direction of the detected object...