I want to make a mailman detector for my mailbox. Ideas?

Projects General Guidance
1

I want to make a device I can put inside my mailbox to send me a message when the mailman leaves something. I'm not sure if this is entirely legal; it's important that it at least doesn't look like a bomb or scare the mailman in any way.

All I need to do is have it detect when the door is opened and send a signal about 200 feet to another arduino with an indicator light or something.

By biggest constraint is that I've got an apartment box so I can't attach anything (like an antenna) to the outside of the box. I'm not sure if a simple radio module would be able to sent anything out from inside a metal box. (maybe transmit when the door opens?). I also couldn't put a solar panel on it for power.

It would need to use very little power so it wouldn't need to be recharged every day.

I'm thinking maybe an ultrasonic sensor or light sensor and a 433MHz transmitter would accomplish this.

2

Its the sensor that would trouble me, how to know its a mailman who has left the post as apposed to a mailwomen.

3

srnet:
Its the sensor that would trouble me, how to know its a mailman who has left the post as apposed to a mailwomen.

A harpoon with a needle takes a blood sample. \s

4

Since you stated this is an apartment mailbox, is this a single box or part of a group of boxes? The grouped boxes often have a door on the back to open all the boxes at once.

5

Tilt switch?

6

david_2018:
Since you stated this is an apartment mailbox, is this a single box or part of a group of boxes? The grouped boxes often have a door on the back to open all the boxes at once.

It's in a group of boxes. Mine happens to be in a top corner. They have a back door but they pretty much always load from the front.

dougp:
Tilt switch?

The door opens horizontally, so no tilting unfortunately

7

Photodiode

8

Could you put a hinged floor that is held up by a light spring. When a letter falls on it the weight pushes the floor down and closes a switch.

...R

9

Very similar thread.

One of your classmates, perhaps?

10

A mailbox notifier was my first Arduino project. It is still working fine after 4 years and the last battery I put in it was 18 months ago.
I still intend at some stage to publish the design of the project here.

The sensor is a home made mat with 4 flat upward facing IR leds and one TSOP3438 device embedded in it and lies on the bottom surface of the mailbox. The LEDs in turn beam a signal to the top of the mailbox which is reflected down to the TSOP. The transmitter part wakes up every 32 seconds, runs the short test sequence, and transmits the sensor results and battery voltage, back to the receiver part in the house.

The choice of LEDs is quite important. If the beam angle is too narrow, the IR beam is powerful enough to penetrate thin paper which means a missed detection. This requires some experimentation.

The transmitter part uses a barebones ATmega328p and an NRF24L01+. There is a boost converter which is switched on during the test sequence to ensure the voltage to the IR leds is not affected by the battery voltage, which is important for stability.

The receiver part is very simple, consisting of an Nano and matching NRF24L01. I (mis-)use an 5volt sugar cube relay driven at 50Hz to act as buzzer.

In my case, I could mount a waterproof box on the back of the mail box which houses all the electronics (except the sensor mat which is in the main body of the mail box) and the 3volt battery pack.

In the OP's case, I guess the main challenge is getting a signal out of a closed metal box. I'd probably consider drilling a tiny hole in it and letting a small wire out the back.

11

wvmarle:
Very similar thread.

One of your classmates, perhaps?

My thoughts too.

There often very similar threads appearing at the same time.

Would be nice to know which are real projects, that people are actually goping to build.

12

wvmarle:
Very similar thread.

One of your classmates, perhaps?

I'd personally give a poster with over a 100 (substantial - I've just looked ) posts and 3 years membership here, the benefit of the doubt. The typical school projects are usually obvious because of one or more of the following factors:
a) what they are doing appears to have no practical value
b) the OP appears clueless
c) the OP appear disinterested
d) the OP has zero posting history under his/her current screen name.

13

Traditionally, a dog! :sunglasses:

14

Them was the days when the mailman used to blow his whistle....... :smiley: :smiley:
(intentionally wrong verb)

15

6v6gt:
I'd personally give a poster with over a 100 (substantial - I've just looked ) posts and 3 years membership here, the benefit of the doubt. The typical school projects are usually obvious because of one or more of the following factors:
a) what they are doing appears to have no practical value
b) the OP appears clueless
c) the OP appear disinterested
d) the OP has zero posting history under his/her current screen name.

Yep, this is quite the coincidence. I wanted a mailbox notifier because I keep checking for some new 3D-printer parts to come in. I'm a physics student in university, just finished my semester and now I've got some free time. I do this stuff for fun, I genuinely intend to build this.

wolframore:
Photodiode

Not a bad idea, but I'm not sure it'll work in the winter when it's dark at 4pm and using an IR LED may use too much power.

Robin2:
Could you put a hinged floor that is held up by a light spring. When a letter falls on it the weight pushes the floor down and closes a switch.

...R

The would need to be very flat and, I've only got about 4 inches (~10cm) to work with here, and I also need to fit packages in there.

6v6gt:
A mailbox notifier was my first Arduino project. It is still working fine after 4 years and the last battery I put in it was 18 months ago.
I still intend at some stage to publish the design of the project here.

The sensor is a home made mat with 4 flat upward facing IR leds and one TSOP3438 device embedded in it and lies on the bottom surface of the mailbox. The LEDs in turn beam a signal to the top of the mailbox which is reflected down to the TSOP. The transmitter part wakes up every 32 seconds, runs the short test sequence, and transmits the sensor results and battery voltage, back to the receiver part in the house.

The choice of LEDs is quite important. If the beam angle is too narrow, the IR beam is powerful enough to penetrate thin paper which means a missed detection. This requires some experimentation.

The transmitter part uses a barebones ATmega328p and an NRF24L01+. There is a boost converter which is switched on during the test sequence to ensure the voltage to the IR leds is not affected by the battery voltage, which is important for stability.

The receiver part is very simple, consisting of an Nano and matching NRF24L01. I (mis-)use an 5volt sugar cube relay driven at 50Hz to act as buzzer.

In my case, I could mount a waterproof box on the back of the mail box which houses all the electronics (except the sensor mat which is in the main body of the mail box) and the 3volt battery pack.

In the OP's case, I guess the main challenge is getting a signal out of a closed metal box. I'd probably consider drilling a tiny hole in it and letting a small wire out the back.

This is helpful, I'd love to see a detailed post. I don't think I'll be able to get away with drilling holes, but then the door is open it does point in the general direction of my apartment. Perhaps I can use the door itself as a ground plane and have it transmit when the door is open.

16

Then add a switch in the door, that activates the Arduino and starts transmission.

Of course it doesn't tell you there is something in the mailbox, but why else would the door be opened?

17

You do realize that a photo sensor let’s current flow when it detects light? While it’s off you can bias it so theres uA flowing at most. You can set the trip point. I’m sure there is some light near your mailbox especially for an apartment one unless your vestibule is a rare one in complete darkness. It will detect the change in light. Doesn’t need full sun to activate.