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DIY Electronic Birthday Blowout Candles

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Step 1The Circuit

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23 comments

Apr 15, 2012. 3:28 PM

Adambowker98 says:

So, um.... How do you make it? All the steps are blank!

Apr 26, 2011. 11:34 AM

Lithium Rain says:

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

Apr 13, 2010. 2:41 PMpurpulhaze says:

Do i need to be a pro member to see this instructable?

Aug 14, 2009. 9:10 AMwatermelonhead says:

pics pwease?

Jul 11, 2008. 5:20 PM

T3h_Muffinator says:

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.

Jul 11, 2008. 11:03 PM

cedtlab (author) says:

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.

Feb 22, 2009. 2:08 PM

bikeNomad says:

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.

Jul 11, 2008. 9:07 AMbewakoof says:

Awesome work and extraordinary description

Jan 2, 2009. 7:14 AMDerin says:

BOLD

Jan 2, 2009. 7:14 AMDerin says:

'[linktest:// test for links]'

Sep 20, 2008. 8:16 AMemuman4evr says:

Whats a thermistor, never heard of that before.

Sep 20, 2008. 9:36 AM

cedtlab (author) says:

A thermistor is a temperature dependent resistor.
More information is here:

http://en.wikipedia.org/wiki/Thermistor

Thanks,

Sep 20, 2008. 6:57 AMdriesyo says:

(removed by author or community request)

Jul 29, 2008. 5:02 AM

=SMART= says:

Hahahahahaha Cool !!

Jul 17, 2008. 8:38 PMnickstewartroc says:

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)

Jul 23, 2008. 7:31 AM

Culturedropout says:

Just be sure to use lead-free solder and other components. It'd suck to get lead-poisoning on your birthday... ;-/

Jul 23, 2008. 8:37 AM

cedtlab (author) says:

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.

Jul 23, 2008. 10:18 AMnickstewartroc says:

Thats a good idea, i think that is what ill do for my cake :)

Jul 20, 2008. 1:43 AMgauravrewatkar311 says:

good very interesting !!!!!!!!!!! all my regards go to the " IDEA MAN " GREAT THINKING i am expecting something new next month also!!!!!! great job

Jul 17, 2008. 4:41 PMjoshbond_2007 says:

you mean 4x1.5volts

Jul 17, 2008. 9:19 PM

Gadre says:

I mean four re-chargeable (NiCd or NiMH) batteries which are typically 1.2V each, so thats 4x1.2 volts Using 4x1.5V batteries (for example the alkaline ones) would not be advisable since the microcontroller cannot handle 6 volts.

Jul 14, 2008. 2:59 AMpapiya says:

cool..so the modela makes ready to use boards now!..gr8..lots of time saved

Jul 12, 2008. 5:41 AMsotsirh194 says:

Just so you know this was featured in one of my electronics design magazine. It was way in the back and there wasn't much instruction on how to build it.