What about a beam break sensor? That would stay broken for a small post card
There were some small units mentioned in another post recently I think
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noel1983 wrote:What about a beam break sensor? That would stay broken for a small post card ...
berkinet wrote:noel1983 wrote:What about a beam break sensor? That would stay broken for a small post card ...
That would probably work well in a small mailbox. However, the typical french mailbox, like mine, is~ L 300 x D 410 x H 300. So, if the beam were in the center of the mailbox, from floor to ceiling, it would be easy for a letter to land outside the beam. Also, I would have to mount one side of the beam in or under the floor.Something that would cause problems at some point.
However, I could mount both emitter and detector on the ceiling. One at each end of the box, and angled towards the center of the floor,
Something like:
The question is: Would a small envelope cause a significant enough drop in reflectivity to "break" the beam? However, rather than using a binary on/off IR detector, if I could find one with analog output I might be able to determine changes. Worth looking into.
roussell wrote:...Years ago I did this. I lined the bottom and sides of the mailbox with a black velvety (velour?) fabric ...
lanbrown wrote:Two others, look for light. If the box is opened, then light would have been let in. You could get false positives with this though..
rhanson wrote:Cameras are so cheap nowadays, I...
But to answer your original question, what's wrong with looking at a moving average of the analog values?
Lots of nerdery here:
https://stats.stackexchange.com/questions/41145/simple-way-to-algorithmically-identify-a-spike-in-recorded-errors
rhanson wrote:Oh, there have been many iterations along the way: object identification from photo, reflected visible light, reflected IR, distance (light and sound), weight, and endless adjustments.Nearly 5 years on! Wow. (We should pause for a moment of silence in remembrance of the world as we knew it 5 years ago...)...
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