Introduction: Musical Pop Up B'day Cake With Blowable LED Candle

About: Jayanth 21 Maker Audiophile Almost an Engineer Amateur cook

I always have a passion to try new stuff. At the same time I wanted to give my best friend a unique gift for his birthday. So I have made this Instructable, which is a combination of Electronics and Fine Arts. I took around 6-8hrs to complete this project and I really enjoyed making it.

In this instructable, I have made a greeting card. A kirigami paper cake pops out of the greeting card when opened and immediately a birthday MIDI tone plays. The candle at the centre of the cake also glows. When the tone completes playing, the candle continues to flicker. The candle can be blown off after the MIDI tone is fully played. Behind the greeting card there is a QR code struck. Upon scanning the QR code, my friend will be able to access a shared google album which contains the pictures of some of the best moments that we have spent together. If this sounds exciting, I'll teach you too how to make one by yourself. :-D

I am very sure that this will make my friend's best birthday gift, for this can recreate his birthday scenes whenever he opens this greeting card and he will cherish his birthday moments. This gift can also be used for celebrating an eco friendly Birthday party since an electronic candle has been used instead of an actual candle. :-P

Step 1: Materials Required

Electronic Circuitry

>> Digispark USB Board

>>Arduino Board & 12V power supply & 10uF capacitor(If your Digispark board is not genuine like mine)

>>8ohm 0.5w speaker or Peizo buzzer or a Mini Speaker

>>Red LED

>>Electret Microphone

>>Exhausted 9V Battery

>>Multi-strand wires

>>3V Coin Cell CR2032

>>Soldering Kit

Stationary & Other Hardware Items

>>Double Sided Tape

>>Cardboard Paper

>>Rubber Band

>>OHP Sheet or any other stiff plastic sheet

>>Hot glue

>>Sand Paper

>>Small hack saw blade or any other stiff and straight piece of material

Step 2: Electronic Circuitry

The gift contains the above simple electronic circuit attached. The power supply to the micro-controller(Digispark Board) is given with a single coin cell via a mechanical switch. The mechanical switch is designed in such a way that it will close the circuit whenever that greeting card is opened. The pin P0 has an 8ohm speaker connected to it. The pin P1 has a red LED with a 100ohm resistor in series connected to it. The Pin P2 has an electret microphone with a 4.7k ohm pull up resistor connected to it. I used a normal buzzer while testing in the video. But I used an 8Ohm flat and small speaker due to its compactness in the actual greeting card. Since we are supplying just 3 volts to the digispark board, there is no need of voltage regulation. Hence power supply is directly connected to the micro-controller using the 5V pin. Use multi stranded wires everywhere because they offer greater flexibility that single strand wires.

Step 3: Programming Digispark's ATTiny85 Board

I have used the I/O pins of Digispark in the following way:

P0: OUTPUT Speaker


P2: INPUT Microphone

For Programming the Digispark, use the attached arduino code and this link.

If the above method does not work, then use this link.

The standard method of programming the microcontroller using USB described in the first link works if your Digispark board is genuine. In case your Digispark board isn't genuine like mine, then you'll have to try the second link. This link uses High voltage serial programming method to unlock the digispark board's reset pin and enables you to program this board by using an arduino as an ISP programmer. You'll get to know that your board isn't genuine after your computer fails to recognise it even after your attempt to manually install its drivers.

After all the programming is done, you can desolder and remove the power led of the digispark board to save power.

Step 4: Working of the Code

The above attached flowchart can clearly help you understand the simple algorithm that I have used for my greeting card. Refer the attached arduino code to understand the logic that is explained in the flowchart.

In the attached video, I have used buzzer instead of a speaker. I found the buzzer to be bulkier in size and the clarity of the song was not that great. Hence I switched to a speaker.

Step 5: The Mechanical Switch


Rip open an old or exhausted 9V battery and separate the metallic sheet. Using sand paper, try to scratch off all the paint on the metal sheet. Now cut two rectangles out of it and get a curved surface on both of them. Put a rubber band at its centre as shown in the picture and put hot glue on one of it's ends. This makes the female part of the mechanical trigger that we will be using in the greeting card. To make the male part of the trigger, fold OHP sheet or any other stiff plastic sheet into a smaller rectangular piece than the metallic rectangular piece. Place a broken hacksaw blade inside the sheet and tape it from all the ends using a cello tape. This is done to make the male part of the mechanical trigger very stiff. Now solder two wires on both the sides of the female trigger. Using OHP sheet, make a small path for the male part to enter the female part. Stick the female switch on the right side of a folded cardboard paper using double sided tape or hot glue. Also stick the pathway on the right side using cello tape. Now stick the male part of the trigger using cello tape on the left side of the folded card as shown in the picture. Stick a small magnet on the female trigger just to achieve spring action by the metallic sheet.


Whenever the folded cardboard is opened, the male part of the mechanical trigger swiftly moves away from the female metallic trigger through the pathway. Now both the metal sheets of the female trigger come in contact with each other and this action enables the power supply to the circuitry of the digispark board. Whenever the cardboard is closed, the male part enters the female part and separates the female metallic plates which were once touching each other and this action disables the power supply to the circuit.

Step 6: Kirigami Cake

The complete credits for the Kirigami Birthday cake goes to Lino Efrem Xavier Gomes.

Stick all the components except the LED, the microphone and the coin cell using double sided tape on the cardboard paper as close as possible.

Use this link to make the cake and stick it on the carboard that you made in the previous steps. You can use two stuck 100gsm papers instead of a single 160+gsm paper if it is unavailable in your locality. While sticking the candle, make sure that the LED that was mentioned in the schematic passes through the candle. Also the microphone must be struck on the paper cake using a little hot glue. For that you need to make a hole that is as large as the microphone on the paper cake. Make two small holes to send the power supply wires through the greeting card. Connect the coin cell to these wires and stick it behind the greeting card. Refer my pictures to get more clarity on the above instructions.

Step 7: E-Gift Using a QR Code

This step is optional. But I strongly urge you to include it in your greeting card too. The reason is simple. After repeated usage of the greeting card, the battery will get exhausted one day. But inorder to keep the greeting card still in working condition and preserve its charm, the QR code is required. You may embed an E-Greeting card or a shared google album like what I did through the QR code. This E-Gift stays as long as the gift is preserved.

To generate the QR code, visit,

paste your link of shared album in google photos and click to generate the QR code. Print a small sized code of the same and stick it behind your greeting card in such a way that your battery gets covered. Refer the attached pictures to get more insight regarding the above procedure.

Step 8: Conclusion

Add your message in the front most page of your greeting card and keep it inside an envelope before gifting.

Feel free to ask any doubts that may arise during the making and expect a reply to it within a day or two.

Thank you


For the birthday midi tone code for arduino

For the kirigami template

First Time Authors Contest 2016

Participated in the
First Time Authors Contest 2016

Homemade Gifts Contest 2016

Participated in the
Homemade Gifts Contest 2016

Arduino Contest 2016

Participated in the
Arduino Contest 2016

Make Noise Challenge

Participated in the
Make Noise Challenge

Make it Glow Contest 2016

Participated in the
Make it Glow Contest 2016