Step 1 The Circuit
Step 2 Building the Circuit board
Step 3 Soldering the Circuit board
Step 4 Programming the Micro
Step 5 Using the Candles
To power the circuit, you need 4 batteries of 1.2V, AA or AAA size or 3 batteries of 1.5V (AA or AAA size).
Using the blowout candles is easy. Of course you need a cake to be able to use the candles :).
Read more: DIY Electronic Birthday Blowout Candles