Discussion in "Project Help" started by    cenadius    Aug 19, 2007.
Sun Aug 19 2007, 03:20 PM
Can some1 teach me ho to do this hardware?what code should i write for this hardware?
This assignment as mention in the title,we need have the function as below:

-The system has 2 modes of operation: manual and automatic.
-In manual mode, a user may control the speed of the fan (either off, low or high speed) via push buttons.
-In automatic mode, the microcontroller controls the speed of the fan depending on the ambient temperature:
Off Temperature < 30ºC
Low speed30ºC Temperature < 40ºC
High speedTemperature 40ºC
-Regardless of the mode of operation, the ambient temperature is always shown on a dual-digit seven-segment display modules.ion
and what additional function can i add for this fan?I am very weak in doing this type of project...
Hope some1 can help me and thanks for helping
 tienduhieu like this.
Sun Aug 19 2007, 08:55 PM
hi cenadius,
welcome to rickey's world
talking about your assignment.. first of all.. decide which hardware to use.. i mean.. the temperature sensor, fan interfacing technique..

only after that.. writing a program for that hardware can be done. Also which language you want to use? C or Assembly?
 tienduhieu like this.
Mon Aug 20 2007, 12:54 AM
Hi Ajay,thanks you first for trying to help me.
i only allowed to use assembly language to do this project and i will attach the part list to be use for you.Hope u can teach me how to do after see the electronic part that i will use in doing this project.Can i know what is fan interfacing tehniques means?sorry, i really very weak in this subject,so many term that i not understand.

[ Edited Mon Aug 20 2007, 12:59 AM ]
 tienduhieu like this.
Mon Aug 20 2007, 06:29 AM
hey cenadius since u r using dc fan... so its a very easy task.what u have to do is analog to digital conversion and then pwm according to temperature from lm35.in c language its very simple task
 tienduhieu like this.
Mon Aug 20 2007, 10:39 AM
As said by abbas, the controlling DC fan can be done through a PWM on a pin. and reading LM35 is easy with the help of ADC. All you need to do is the calibration of temperature with the ADC o/p.
you can start building your schematic. Just try it once
 tienduhieu like this.
Mon Aug 20 2007, 12:14 PM
Can i know what is PWM mean? :-s
 tienduhieu like this.
Mon Aug 20 2007, 12:45 PM
PWM is Pulse width modulation.. it helps you to control the output voltage by varying the width of a square wave pulse..

A Brief Description:

|¯¯|__|¯¯|__|¯¯|__ --->
 A square wave


Ttotal = ton+toff

Duty cycle d = Ton/Ttotal

if Vin is the input voltage and Vo is the o/p voltage.. then

Vo = d x Vin
where d is the duty cycle..
now if we vary the duty cycle we can control the o/p voltage
e.g. d = 0, then Vo = 0 -- o/p is zero
and if d = 1, then Vo = Vin -- o/p equals input
Now the value of d can never be greater than 1.
To control d, we need to control the Ton, if we reduce the value of Ton, then d decreases and hence Vo. similarly if Ton increases, d increases and hence Vo increases.

So d is directly proportional to Ton.
Vo is directly proportional to d
hence Vo is directly proportional to Ton

I hope you understood the concept of PWM. :-)

[ Edited Thu Jan 17 2008, 06:33 AM ]
 tienduhieu like this.
Tags pulse width modulationPWM8051 PWM code
Wed Aug 22 2007, 01:38 AM
Thanks for ur explanation.This is the schematic that we need to use.Pls help me see got any problem?if i wan add other thing such as buzzer,how to add?Can u teach me how to write the code by using asembly langugae for this assignment?thx

[ Edited Wed Aug 22 2007, 12:26 PM ]
 tienduhieu like this.
Wed Aug 22 2007, 11:14 AM
as the schematic is ready.. so you can start programming one by one.. which one you want to go first? write programs in small modules... and then combine them later on.
 tienduhieu like this.
Thu Aug 23 2007, 04:55 PM
-The system has 2 modes of operation: manual and automatic.How to write the code for this function?teach me pls

 tienduhieu like this.

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