Mail Minder Project Details

Problem:

The problem is not knowing if we have mail, so we have to walk to the end of our driveway to check it.  What a waste of time!  This problem is amplified by the fact that we live on a busy county road, so waiting for traffic gaps is part of the process.

Solution Concept:

Create an IOT enabled Smart Mailbox that tells us if we have mail thereby eliminating unnecessary trips to the mailbox.

Features:
  • A sensor plate that becomes the new floor of the mailbox.  This sensor plate has 3 Vishay VCNL4040 Infrared Proximity sensors to detect the presence of mail.
  • Extended range wireless data link to house using RFM69HCW Radio Modules @915MHz.  WiFi signal can not handle this distance.
  • Battery operated, this a Solar Charging station is needed.
  • RTC (Real Time Clock) is incorporated so that system only checks mail during 7am to 9pm window, thus conserving battery.
  • Weatherproof box for electronics. (Learned some lessons here)
  • Initial ideas that were rejected along the way include: Temp.Sensor, Ambient Light Sensor.
Sensor Plate with Top Cover
3D Printed Sensor Mount

Sensor Plate:

I created a sensor plate that becomes the floor of the mailbox.  The sensor plate is basically a sandwich of two ‘slick’ resin sheets with the sensor electronics in the middle.

A 3D printed sensor mount was designed and created.  The sensors had to be spaced so that even small postcards would be detected.

A sensor plate that becomes the new floor of the mailbox.  This sensor plate has 3 Vishay VCNL4040 Infrared Proximity sensors to detect the presence of mail.

Electronics:

Components:

1. Moteino Mega (link) micro-controller from Low Power Labs with RFM69HCW Radio module.  Also a micro strip antenna at far right of box from Low Power labs as well.  This antenna is perfectly tuned for 915 MHz.

2. SparkFun Nano Power Timer – TPL5110 (link) nano power Controller to help conserve battery life.

3. SparkFun RV-8803 Real Time Clock Module (link)

4. Marv’s Minders Interface board (green PCB) designed to work for a variety of projects that use the Moteino Mega footprint.

There is also an extra CR2032 coin cell battery added in parallel with the RTC battery for good measure. 

 

Alerts

Most alerting is thru my Node Red dashboard.  For this project I incorporated an iOS app called ‘Complicated’ which allows me to update my Apple watch with Minder status values.

Implementation v1.0

No… its not mounted backwards, its a double door mailbox.  After several months of usage, the Mail Minder continues to work perfectly.

But wait... see below…

Mail Minder Final Install. (Double Door Mailbox.)

Project Update v2.0

Due to tragic circumstances… a WIDE LOAD truck damaged the mailbox.  So the door could not close. 

Fortunately, no electronics were damaged.  So I took this opportunity to improve a few things:

  • Improved Solar Panel (See Details)
  • Improved Battery
  • Improved Water Proof Cases for the electronics.
  • Added temperature sensor to control box (not inside mailbox)
  • Software enhanced to detect ambient light indicating the door was left open.
Updated Version with new cases and panel
Control box electronics include nano-power switch and radio board with antenna mount
New solar panel and electronics box with battery
Final implementation v2.0

Project Summary

  • Project works perfectly
  • Project was more complicated due to being battery powered and the need for weatherproofing. Outdoor, waterproof projects are a big pain!
  • I learned more than I wanted to about the characteristics of Polypropylene plastics and how difficult it is to work with.  Practically nothing can be glued to it.
  • Project was complicated by damage to mailbox and I expect it won’t be the last time.