I need a sensor to measure motion of small particles to a close distance. Think of it like stones of diameter between 1 and 10mm falling down a pipe (diameter about 15mm), and I want to be able to measure the event when one passed the sensor (the flow is not continuous, so only one passes at a time).
So the simplest setup would be a sensor that just sits there and gives a HIGH output if it detected motion… My ideas so far where as follows:
- Infrared Sensor: Problem: sensitive to light conditions, I guess not high enough resolution?
- Ultrasonic: insensitive to light conditions, but also not precise enough (?), as I need measurement accuracy to 1mm (the sensor should detect such small particles)
- Photoresistor and light source: should be sensitive enough, but would that work?
I am happy for all suggestions and, hopefully, some proven concepts, if you have any