Arduino Fridge Magnet




Do you have a habit of leaving notes on the fridge, now take it digital and add an Arduino to it.

In this instructable I'm going to show you how to do just that. All you need is an Arduino, an LCD screen and a Bluetooth module to make this and a Android mobile to upload your note wireless. I tried to keep it as small as possible and it is powered by a 9V battery.

Check out my Facebook page and like it to support me.

So enjoy building your own project.

So lets start with getting all the parts.

Parts List:


  • Soldering iron

Step 1: Arduino

As for the Arduino you can use a UNO or a mini, I did not have any spare Arduino mini so I built my own to save space and money. I have a nice in detail instructable on how to do that, so I will leave a link to that. So you can see how my Arduino turned out to be in the above picture, again I tried to keep it as small as I could. I did not add the programmer's part to it as I used my UNO to upload the code to it. You can get a external serial programmer to upload code to it, ill leave a link to that as well.


How to make a Arduino

Serial programmer

Step 2: LCD

Solder connector pins to the LCD and the same type connectors on the Arduino, so that you can easily plug them together. If you noticed that I had to change from the connectors in the previous step to this step a silly mistake that I made. You don't have to connect all of the 16 pins just the ones in the circuit will do.

Step 3: Circuit

Once you have done soldered the pins follow the circuit and connect the LCD to your Arduino. If you used a UNO I recommend soldering it on a prototype shield. I had the rheostat substituted with a resistance, the rheostat is used to adjust the contrast. You can find the proper level, in the following steps.

1)Complete the circuit connections

2)Upload "Hello World" code as in the IDE examples

3)Power the circuit and adjust the rheostat till you get a proper contrast.

4)Once you have the proper level, remove the rheostat and measure the value of resistance with respect to ground and LCD pin 3.

5)Replace the rheostat with the measured value of resistance.

Step 4: Bluetooth

Once you have the "Hello World" successfully working on your board. Now its time to connect it to your Android phone. To connect it you need to attach a Bluetooth module I got mine from eBay, but I had to make certain connections to the board to get it function as required, I'll set up an instructable on how to do that soon. You can go for Bluesmirf if you don't want to make any changes.

Step 5: Code

The code for the project can be found in the IDE examples named "Serial LCD", if you can't find it just copy and paste the code as below:


// initialize the library with the numbers of the interface pins

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
// set up the LCD's number of columns and rows:

lcd.begin(16, 2);

// initialize the serial communications:



void loop()

// when characters arrive over the serial port...

if (Serial.available()) {

// wait a bit for the entire message to arrive


// clear the screen


// read all the available characters

while (Serial.available() > 0) {

// display each character to the LCD





Step 6: Voltage Divider

This is an optional step and not required if you use an Arduino UNO. It is a 5V regulator that I had to setup since the atmega 328 IC requires 5V input voltage. A UNO has a built in voltage regulator.

To create it just follow the circuit and try to keep it as small as possible.

Step 7: Wood

Once you have completed setting up everything now you need a wood to which you need to glue it on. I did not use wood but some kind of a cardboard, I have no idea what they call it if you know leave a comment. The material I used is lighter and slimmer than wood.

Step 8: Glue

Time to get the circuits on the wood, If you notice I used double-sided tape to get it stuck. I don't recommend using double-sided tape but recommend using hot glue. The magnets are also stuck the same way, get strong magnets because you don't want the device to keep falling off when you slam the door. I used three magnets which gives it a stronghold.

Step 9: Android App

I have created and Android app to go with the project, the app can be found in the attachments. Make sure you have "Install from unknown sources" ticked on your android phone settings. This app was created in MIT App Inventor so it can be edited by everyone, If you want the up to date blocks leave a comment.

Step 10: Finishing

After you have completed everything you should be able to run your project easily and leave easy reminders and notes. If you have any problems try to check back the steps, and leave comments if you still can't get it. IF you make your own don't forget to share it and click "I Made It".



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19 Discussions


3 years ago

Ingenious, not to mention useful.


3 years ago

hello my friend i made it to . but i want to have the .apk code please

Hi ThisIsSteve, Very nicely done! I can picture myself in bed at night, cellphone in hand leaving notes for the kids to find next morning before school. Or jotting down a few groceries or chores, whatever. Simply a wonderful idea, one of the most useful ibles I've seen in a while.

Two suggestions, if I may, #1 attach a barrel jack in order to connect to a suitable wall wart for reliable power supply. Of course the power cord would of necessity wrap around the fridge on the hinge side & not across the door opening! held up maybe with a few more neodyniums & #2 possibly a larger message area - 20 x 4 lines? Personally, I would like a screen the kids & I could draw on but then we're talking pricey.

I appreciate your posting this instructible & am quite looking forward to trying to produce my own version, for better or worse!! lol - T Tinkerer


4 years ago on Introduction

To fix the code : replace first line with "#include <LiquidCrystal.h>"

To get the bluetooth working, I found a HC-06 on amazon for Arduino, connect 3.3V to vcc Gnd to ground tx to rx on the arduino, rx to tx on the arduino and you are good to go.


4 years ago on Introduction

You may need to connect voltage to pin 16 and ground pin 17 to get the LCD backlight to work. Next on to bluetooth.


4 years ago on Introduction

You don't explain how to get the bluetooth you have running. I bought an identical one to the one shown in this instructable, but I am not sure how to make it work.

"but I had to make certain connections to the board to get it function
as required, I'll set up an instructable on how to do that soon."

Can you point me in the right direction?


How cute arduino is... great idea...

I have a question!!

Is there no need 3.3V for your little cuite arduino?


4 years ago

great idea, there comes to mind one small issue. Due to the magnetic field from the three magnets your battery life is greatly reduced, might i suggest a thin sheet of steel between the magnets and cardboard to reduce and redirect the magnetic field that goes to the battery. It wont stop the drainage completely but will definitely help.

4 replies

Reply 4 years ago

ps im not trying to criticize at all, i love the idea.


Reply 4 years ago

all magnetic fields tend to drain batteries. the stronger the field the bigget the drain. they are small magnets but i would just use a thin sheet of ferrous steel just as a precaution.


4 years ago

Hey great project
Can you give me the app inventor source code because i have modified the project and i want to midify the app to my requirements. Pls i would appreciate if u do dat for me


4 years ago

Nice ! what is the battery life ?

Okay I have to try this. I already have made my own Arduino (I call mine the
Fauxino) and the rest of the parts. Just have to find the time. But
really this is cool beyond words!