I live in a cul-de-sac in a condominium complex, and all the mailboxes are at the entrance to the cul-de-sac. Here's a picture of the setup showing the back side where the postman stands:
I want to develop a device that shows a visual indicator that the postman has been there. That's so people driving into the cul-de-sac can stop and check their box if he's already delivered the mail, but not if he hasn't.
I have zero experience with proximity sensors. This one will have to work in all types of weather, and from what I've read, an ultrasonic sensor seems the right choice. Does that sound right? It would be placed right above where the postman stands when distributing mail into the boxes, facing directly down at the stone walkway, and would give a different reading if he's standing there.
Can someone recommend a sensor that runs on 3.3V, and doesn't draw much current?
Or if there's a better way, I'd like to hear about it. Thanks for any suggestions.
Percipitation looks the same to sound as Santa Claus, the postman, opossum and theives. Any of the dozen Ring cameras in the Cul-de-sac can stream live postman-cam.
An ultrasonic sensor like the JSN-SR04T is a good choice for detecting the postman, as it's waterproof and works in varying weather. It runs on 3.3V with low current draw, making it efficient for your project. Alternatively, consider PIR or pressure sensors for motion or weight detection, which could also work well in outdoor conditions.
I felt a bit uncertain about PIR because I wasn't sure how well it would do outside in direct sunlight, with passing clouds, etc. But I don't really know exactly how they work.
I'll look again for how a door contact might be done. I can't do anything that would get in his way or otherwise interfere with the mail delivery. But if I could rig up a magnet and a reed switch, that would greatly simply everything, and make the batteries last longer. With a sensor I would have to power up at least every few minutes and see if he's there. But a switch would just trigger a powerup when he opens the door.
Well as it turns out, there's not really a good way to detect the door being opened that wouldn't get in his way. So I think I'm back to detecting him from a small distance above with an ultrasonic detector. I should clarify that this is for everyone in the cul-de-sac, not just me, so phone notifications aren't really an option. I just need a visible indicator that doesn't use any power. Working on that now.
