By Anne Christin Braun • Nov 24, 2015

Ever Wondered How Much Letter Mail You Get During the Year?

We always love to learn about new ways to implement PRTG and have seen quite a lot of great usage scenarios in the past. Naturally, we were really excited when we heard that Andreas Ginther set up a Letter Count Sensor "Smart Post Box" for his private mailbox! It tells him not only when he receives a letter, but also when the mailbox is emptied. This way, he always knows if he needs to start looking for the mailbox keys once he gets home.

Here is how it works: If a letter is posted, an email is sent to the mailbox owner and an installed LED lamp lights up. After the mailbox has been emptied, another notification email is sent and the LED lamp turns off again. Besides the email notification and the LED lamp, Andreas has PRTG Network Monitor record daily, monthly and yearly statistics. This way he knows at a glance how many letters he has received in the past.


With this clever system it is possible to count one letter per second. No matter if a whole bunch of letters are sent on a certain day or if somebody posts a really small one - the Letter Count Sensor can't be tricked. There are two special light sensors that recognize even small letters and while the post box is open the sensors don't scan for letters in order. This prevents PRTG from producing inadvertent error reports.



Andreas uses a script as the main program that queries the IO processor connected to the sensors and an email agent as a secondary script. Both scripts are running on the Home Automation Server. Furthermore, he has a virtual instance of PRTG running. The main program's job is to write the number of letters and door actions in a local database. A PRTG Custom Sensor starts a script that receives the details about the amount of letters that were posted.

Applying this method, Andreas learned that he had received 275 letters during a period of 10 months with July and August being the slowest months. While on the go, he simply relies on the PRTG mobile apps that tell him exactly when it is time to check the mail box.

Needless to say, it is quite a handy service to always know the status of your mailbox, no matter where you are. This solution was not free unfortunately. Altogether, Andreas spent not only over 40 hours on the engineering of the electronic and mechanical components of the system but also about 1000€ for all the equipment he needed. A design goal was using no wireless components to improve reliability. Luckily PRTG was not an expensive part of the solution as the free 100 sensor license was sufficient for the project.


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