# DIY Electronic Birthday Blowout Candles

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## 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

Hi!

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!

Best,

Nicole, Community Support Manager

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

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

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.

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.

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.