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22 Jan 2015, 9:24

Mail Box Notification with Arduino Wi-Fi shield and ThingSpeak (IoT) Platform



Have you ever been bothered to check your mail box daily when you having important letters coming in?  How do you feel when you open the box but there is no expected letters? This is the idea behind this Mail Box Notification Project. With the support of this project, you can access the status of your mail box from your office, on the way home or even when you are overseas. In this project, it will automatically filter away the flyers and count the number of letter and upload the data online.

The project is being developed on the open sourced Arduino Platform. The Internet of Things (IoT) function is being enabled by an Arduino Wi-Fi shield. The hardware circuit detects the weight in a letter box. Based the number of increasing above the threshold in the reading, we will be able to know the number of letters present in the mail box.

Components Required


Manufacturer No

RS Parts No Quantity
Arduino Uno - 7697409 1
Arduino Wi-Fi shield - 7697395 1
Instrumentation Amp INA125P 6605232 1
Load Cell FX1901 8937398 1

Introduction to the Componets Used

Arduino Uno

The Arduino Uno is a microcontroller board based on the ATmega328. It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with an AC-to-DC adapter or battery to get started.

Resources: Arduino Uno Datasheet

Arduino Wi-Fi shield:

The Arduino Wi-Fi Shield allows an Arduino board to connect to the internet using the 802.11 wireless specifications (Wi-Fi). It is based on the HDG104 Wireless LAN 802.11b/g System in-Package. An AT32UC3 provides a network (IP) stack capable of both TCP and UDP. The Wi-Fi shield connects to an Arduino board using long wire-wrap headers which extend through the shield. This keeps the pin layout intact and allows another shield to be stacked on top.

Resources: Arduino Wifi Shield Datasheet

Load Cell (FX1901):

The FX1901 units are intended for OEM use in laboratory, hospital or consumer product applications, establishing a breakthrough price/performance value for compression load cells. The FX1901 is a 1% load cell device with full scale ranges of 10, 25, 50 or 100lbf compression. The following schematic shows the internal connection of the load cell. It is a full Wheatstone Bridge circuit that gives more accurate readings.


Resources: FX1901 datasheet



In this project, we have used a load cell to measure the difference in the weight. Whenever the difference in the weight is higher than the threshold value, it will cause the number of letter increase. We have used a very thin piece of wood to be the base. This is because the wood piece is very thing, any weight acting on it will cause slight bent in the wood.  This will be detected by the load cell located underneath the wood. There are four small wood squares at the corner to support the wood piece.  The wood piece can be put into a mail box to detect the letters present. 



We have prototyped the circuit on the strip board to amplify and process the data gathered from the load cell. The instrumentation INA125P is used to amplify the data gathered from the load cell. The resistor used is to set the gain desired. At the same time, we have used DesignSpark PCB to design the circuit as well.

Schematic Design


PCB design


We have used single layer board as the connection is not so complicated and to reduce the production cost.



In this project, we have used Arduino, an open source platform, to process the data and control the output. The wireless function is being enabled by the extra Wi-Fi shield. This allowed the user to access the data regardless of the time and location.

We have uploaded the data to the IoT platform, thingspeak, a free IoT platform. After you have created your own channel, you can upload the required data to the channel.  This allows the user to monitor the data sent by the Arduino wirelessly. Hence, it can give users the required information about the status of letter box.


There are two charts in our channel for the user. One is the raw voltage output sent by the Arduino. It shows the voltages change in the letter box. The other one on the right is showing the user the Number of letter inside the mail box.


Please watch the following video for a short demonstration of our project. 

Hope You Enjoy this Project 


22 Jan 2015, 9:24