I have a small side project using Arduino (pro mini or nano) that would detect passing model race cars (and quadcopters) and counting how many times it passed through a selected location. I thought of using IR emitters and detectors (photodiode) to achieve this but I'm worried it might not be fast enough or it might miss some counts.
The setup would have a few (1 or 3) IR emitters on one side of the road and a detector on the opposite side, facing the emitters (or maybe the emitters on top, and detector on the bottom). They would be more or less 1 foot apart and the toys would pass in between (there is also an arch about 1ft and all of them should pass under the arch). I'm using these for the emitters and these for the detectors.
Only one car would pass through the track at any given time so there would be no issues arising from use of multiple cars.
The toys are about 4-5" length and width, and height of a quadcopter would be around 1-2".
Basically, just detect any brick-sized object passing through the arch.
Is there something I could do to guarantee a count and would IR even fit this type of application? Or should I use an alternative? If so, any suggestions?
Thanks in advance
Best Answer
As far as the speed, IR detectors are definitely fast enough with response time being of the order of ns or us (if you use more filtering). There are a couple of areas of concern:
1) The pattern is probably close to being omni-directional (I could not see the datasheet that would show this) so you may have issues with the signal bouncing off of the floor, other objects and would have to experiment a lot with thresholds.
2) It is likely that the signal would not increase/decrease monotonically as the car is passing by, so you would have to implement some sort of a debounce function to avoid multiple counts for the same event.