DIY Electronic Birthday Blowout Candles




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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 :).

We organized a fictitious birthday party with a virtual cake to celebrate the project and a video of that party and the birthday candles

If the video isnt working, you can try this youtube link: Birthday Candles Video

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    25 Discussions


    Hey, this is a great Instructable and is very informative. Just one thing is missing... pictures! It really helps a lot when trying to follow directions so you should consider taking some photographs. Once you do that leave me a message so that we can publish your work.

    Thanks for the cool Instructable and we hope to publish this soon!


    Nicole, Community Support Manager


    5 years ago on Introduction

    pic would truly be awesome as well. not just blank steps. but ill chalk it up to being new to the instructables, an 4getfullness.

    Lithium Rain

    8 years ago on Introduction

    Hey, you have a bunch of blank steps on here. Nobody can figure out how to make this. It's very sad T_T


    This looks awesome! I'm just wondering - where's the analog input pin of the uC? I looked at your schematic and it seems as if you just have it in a resistor network on VCC.

    2 replies

    Reply 11 years ago on Introduction

    Hi, Thanks for your comment. Tiny45 has several analog input pins. Pin1 (is PortB5 and is also ADC0 input ) is one of them. We used that to read the voltage at the junction of R3 and R4. R3 is the thermistor and R4 is a fixed value resistor. Since the other end of R3 is grounded, as the thermistor cools off, its resistance increases (the thermistor is an NTC, i.e. has a negative temperature coefficient) and so the voltage at the junction of R3 and R4 increases.


    Reply 10 years ago on Introduction

    Why bother with the heater (R2)? It's a big load on the battery (though so are the LEDs...) and shouldn't be needed. Did you try using self-heating?

    By using the self-heating of the thermistor itself you should be able to detect the cooling caused by air movement.

    Just run enough current through the thermistor that it heats up a few degrees above ambient (and not enough to damage it), and look for quick changes in the port voltage.

    You'd be best off to use a much smaller thermistor, though (perhaps something like this cheap thermistor.


    This is AWESOME i think i will have to make this and put it on my birthday cake since its coming up in a month(August 12)

    3 replies

    Reply 11 years ago on Introduction

    what we are planning to do is to put the electronics and batteries in a food grade plastic box with just the LEDs and sensor sticking out.