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Term Project - Air Conditioner (of Some Sort.) - any aid is welcome.

marcusaurelius

Dec 13, 2016
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Dec 13, 2016
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To introduce myself, I am a sophomore electrical engineering student.And I am required to design an air conditioner for my term project. Normally this thing is done in groups of two, but my partner is (which i didn't know when i picked him) kind of (absolutely in fact) useless. So now i am stuck with something that i know little about.

The project is schematically as follows :

Sensing Unit -> CONTROL UNIT -> Heating and Cooling Functions.

Temperature Adjustment Unit ---> CONTROL UNIT ->

Basically sensing unit (operating with an LM 35 chip) detects the outer temperature and yields a dc voltage directly proportional to temperature in celsius (eg. for 27 degrees of ambient temperature, it yields 270mV)
Temperture Adjustment unit is where input occurs. User sets (using buttons or whatever) a square wave with a specific duty cycle so that %0 duty cycle wil be evaluated as -50 celsius and %100 duty cycle (simply a DC signal) will be interpreted as +50 celsius. This data will be our desired temperature.

These two pieces of information are then gathered at the Control Unit. This thing compares the two , and if it is hotter than desired, it will run a DC fan (how effective, right? ) and if it is colder than expected it will give current to a stone resistor. The system will stop running when the diffeence between desired and ambient temperatures are less than or equal to 2 degres.

Even though it all may seem a little simple i am very confused. And unfortunately, the material we can use are limited to : (directly copied from the project file) You are allowed to use +/-25 V output of DC power supply and you may use any types of resistors, capacitors, inductors, diodes, LEDs, LDRs, op-amps, transistors, DC motor (without encoder), analog temperature sensor.

So no ardunio. The circuit must be analog. That means more than a few opamps probably.

My biggest confusion is how do i generate a simply adjustable duty cycle with only opamps or other allowed parts? And probably i will need to convert it to DC (depending on the duty cycle.). How do i do that?

Any help is welcome really.

EDIT 1 : Working on it. Will update asap.
 
Last edited:

Alec_t

Jul 7, 2015
3,287
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Jul 7, 2015
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Welcome to EP.
You could start by researching: "comparator schematic", "comparator hysteresis" and "PWM duty cycle".
 
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