Refrigerator Alarm

Introduction: Refrigerator Alarm

“Refrigerator alarm”

Hi guys! This is my first ever instructable I hope you can appreciate every post that I make.

CREDITS to my reference:
Reference: by hertzgamma
Note: Nice work there by the way bro and I really like your instructable!

Please also visit my main blog site at

This device is really simple and here goes…

I. Materials:

x1 Arduino Microcontroller (for this example I used a locally available Gizduino)

x1 LDR 10mm

x1 Buzzer 5v

x1 LED White

x2 1k ohms resistor

x1 5V rechargeable battery (in this example I used a 7V battery but that doesn’t make any difference)

x2 Solderless breadboard (or you could use one if you have a large one)

Cost analysis:

MCU - P550.00 (You may use this for other projects anyway)

LDR - P2.50

Buzzer - P15.00

LED - P10.00

Resistors - P2.00

5V Battery + case - P200.00 (P100.00 ea)

Breadboard - P100.00

TOTAL: P879.50 (May vary)

II. Procedure:

(This is an exaggerated schematic, you may compress the circuit as much as you like so that it really looks like a cool device)

Just follow this schematic in case you get lost. I am working out on a simple book or manual for those who doesn’t know anything about electronics (at all) so that the world will get fair and everyone will know slightly something about it.

If that’s the case, just connect the wires as exactly the way you see it in this schematic. Alright?


Buy the materials! :)

Now where did I buy the materials? Since this blog is intended for all races, I will suggest certain stores for everyone.

For Filipinos like me, buy it simply in eGizmo! and some can be bought in Raon. Yes sir, this is the tough part of the project.

For other people, you can buy these materials simply via Radio Shack. A Filipino like me don’t have an unlimited access to one of the most renowned electronics stores, and you guys are actually lucky for having one! :)


Place the circuit on a breadboard!

There is no need for step by step for this part since the schematic is provided. Just do it exactly as you see it.


Program it!

Of course the device will not work unless you program it in arduino.

Download arduino in this link:

And if you are going to use gizduino, you have to use this patch included if you buy the gizduino. It can also be located here:

These links are virus free I assure you and the download is not really heavy so it doesn’t consume a lot of space on your HD.

Once you have downloaded the software, connect the MCU (microcontroller) to the computer using a USB A to USB B connector (the one usually used for printers). But wait, check first the serial port if your computer have actually seen your MCU. If not, download the drivers first, (it’s because some computers actually have the drivers installed initially)

After that, you should see your MCU detected by your computer via Tools > Serial port > Com(1/2/3/4), then select it. Also, select your board, depending on the specs of the board you bought.

Now you are ready, Run > Copy the codes below > Paste > Verify > Upload.

// Refrigerator Alarm by D

void setup()


//Serial.begin(9600);     // If ever you wanted to check and calibrat


  pinMode(14,OUTPUT);     // LED pin


  digitalWrite(14,HIGH);  // LED indicates that the device is working


void loop()


  int LDRreading = analogRead(A5); // Variable for LDR input

//Serial.println(LDRreading);      // Uncomment if serial monitor is necessary

  if(LDRreading>=50)               // Is the fridge open?


  delay(5000);                     // Time before alarm sounds.

  tone(3,300,1000);                // Send an annoying alarm!




If you have followed all the instructions, then you will actually be finished in no time. I shall post a MORE EXPANDED and MORE DETAILED tutorial once I had the time I promise. But feel free to ask questions so that you can follow this post.

I shall also post a video soon of the device in action so you will get more interested on this project.

Thanks and good job on your new Refrigerator alarm!

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    Thank you for the suggestion sir! And I agree with your opinion. It was just a rush attempt to make an instructable and I plan to improve it soon. In my humble defense, I was starting to figure out the features of the site and I'm trying my best.
    It is similar to hertzgamma's Fridge door alarm. It sets off an alarm whenever the door is left open.


    you should probably wait until you have time to publish a more put together instructable.
    I have one question. What does this thing do?