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Need a small 12v heat source for simulated HVAC project

Okay, so for our year end micro controller project we need to control a temperature inside two 2L pop bottles connnected together. We have a computer fan mounted at the end of the "heating bottle" which needs a heat source in it. The fan will blow the hot air from "heating bottle" into "temperature bottle" which contains an analog temperature sensor. We have to control a set reference temperature point in "temperature bottle" using a PIC16f690 microcontroller by manipulating the fan speed and heat ON/OFF. Problem: I need a decent heating source inside "heating bottle" . Ive been using 12v automotive lightbulbs which work great for a minute or two but then die out. My crappy power supply can only pump out 1 amp, could this be why? Any suggestions on what to use as a heat source? I was thinking some 5w resistors but classmates have said our power supplys cant handle them either. Thanks in advance!

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tech-king9 years ago
solid state relay.... do you mean scr? or triac? and good for you.
. SSR at Wikipedia.
Korey (author)  tech-king9 years ago
Nope, i mean solid state relay.. It says right on the relay
Korey (author) 9 years ago
I ended up getting a 5v solid state relay that works amazing. I was then able to hook up a 60w lightbulb and it works perfect! Valuable learning experience none the less...
CIMG1612.JPGCIMG1615.JPGCIMG1613.JPG
westfw9 years ago
I don't understand why your 12V bulbs are burning out. NM implies that you broke the bulb and let air in, but you don't say that.... 12V at 1amp is 12W, so in theory, all you need is a 12ohm power resistor (say, 20W) which will make a fine heat source. (or you can use a combination of smaller resistors that work out to the same values, like a series chain of 12 2W 1ohm resistors.)
> NM implies that you broke the bulb and let air in, but you don't say that... . Not sure how I came to that conclusion. On re-reading the post, it certainly doesn't say, or even imply, that. Oops.
that'd work You wouldn't get any hotter using any other source inless you increase your wattage.
NachoMahma9 years ago
. 12V filaments will always burn up quickly in air (when run at 12V). You can extend the life by lowering the voltage, but this will decrease the heat output. . A 120V filament will probably last long enough for your project. Or steal the heating element for a small space heater - you'll probably need to shorten it a bit. . If your PS is limited to 1A then the resistance of the heating element needs to be 12 ohms or greater.
Korey (author)  NachoMahma9 years ago
I would like to use a 120v filament, but i need a way for control ON/OFF with a 5v output from the PIC microcontroller...and dont know how. The bulbs all have a resistance of 2 ohms, so that explains that problem
tech-king Korey9 years ago
a transistor acting as switch! energize the base through a 1k resistor to turn power from the collector to the emitter on. ground it (de-energize) to turn it off.
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