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Author Topic: Controlling AC Fan Speed based upon Temperature  (Read 744 times)
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Hey Forums,

** Preamble (ignore this if you want to) **

I'm trying to get into Arduino hacking. I'm quite the noob with electronics but I am a web programmer by trade. I write mostly in PHP, Mysql and Javascript but once in a while I have to do some HTML/CSS as well. At any rate, I'm familiar with code and I have completed a 10 step tutorial booklet that came with my Arduino kit. My kit contains a bunch of motors, breadboard, temperature sensor and some other little gizmos that were part of a great introduction to electronics and the Arduino. So I have some stuff already. This is what I purchased (http://www.canakit.com/arduino-professional-kit.html)

** Actual topic **

I'd like to build my brother a simple system that controls a fan on his heating system. It should be a fairly simple project. Based upon a certain temperature I want to be able to turn on an AC fan. The fan is fairly low wattage (http://www.princessauto.com/pal/product/0772889/Single-Speed/8%22-Duct-Booster-Fan). The only part right now that I'm confused about is how do I piece this all together?

1. What do I put the Arduino actually in? Is there some common Arduino housings that people use?
2. What Power Source will I need to use? Can I use 1 power source for the Arduino and the Fan?
3. How do I switch on 120v devices? Is there a simple cheap relay that would work for this?
4. How will I adjust when I want the fan to come on (like at what temp) and would I see what temperature it is. Would I need and LCD screen? Buttons to modify some settings?

I know there will be many solutions to each part so I'm just asking you to let me know how would you do all of this and why.

I thank yee in advanced.

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Quote
1. What do I put the Arduino actually in? Is there some common Arduino housings that people use?
Whatever you need to protect it from whatever it needs protecting from. No, there isn't.

Quote
2. What Power Source will I need to use? Can I use 1 power source for the Arduino and the Fan?
The fan is AC. The Arduino is DC. What do you think?

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3. How do I switch on 120v devices? Is there a simple cheap relay that would work for this?
There are relay kits, that include the relay and the transistor needed to control the relay. There are SSR relays that can can be directly used with an Arduino. Simple, yes. Cheap, not necessarily, although I don't think cheap should be a criteria. Inexpensive, perhaps. Cheap, no.

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4. How will I adjust when I want the fan to come on (like at what temp) and would I see what temperature it is.
Depends on what hardware you want to use. Switches allow incrementing and decrementing in discrete steps. A potentiometer would allow a more uniform control. However, measuring the actual temperature is more of a concern than being able to define/adjust a set point.

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Would I need and LCD screen?
If you want to see some data, then, yes.

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Buttons to modify some settings?
No. Buttons are to hold shirts closed. Switches are electrical devices. Might as well start with getting the terminology straight.

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I'm just asking you to let me know how would you do all of this and why.
I think you have your priorities backwards. Getting the actual temperature was not something you even mentioned. Your first question was about the packing of the finished product, which really should be the last thing you worry about.
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For project boxes, I like to use old cigar boxes.
You can find them in thrift stores or junk shops
They are easy to cut holes where you need them.
Or you could try this box from Adafruit.
http://www.adafruit.com/products/337
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For your temperature reading, it depends on your range but I found out that a car "engine coolant sensor" can handle pretty much everything. You can check at your local scrapyard for one. You can also use a thermistor for smaller and lower temperatures, but mount it wisely.

For your code, you should make a "truth table". Like :

TEMPERATURE    SPEED
85                      5%
90                      15%
95                      40%
100                    85%
105                    100%

And use delays to allow big variations, you will kill your brother's ears with the variation of the fan speed smiley-razz

Now for your code !

You need inputs : Thermistor (LM35DZ)
You need outputs : PNP Transistor (2N3904)
You need constant (Positive 5v) and Negative (ground)

Set your pins accordingly (thermistor = analog input, pnp transistor = digital output)

Now check tutorials, etc and try to do it by yourself, you're always happy when you are 100% involved.
« Last Edit: January 30, 2012, 01:05:36 pm by expertmax » Logged

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