10-02-2012, 01:05 PM
AUTOMATIC SPEED CONTROLLER FOR FANS AND COOLERS
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INTRODUCTION
This is a device to control the speed of fan and coolers automatically. The
device presented here makes the fan run at a full speed for pre determined time. This
speed is decreased to medium after some time and to slow then onwards after a period
of 8 hours, the fan or cooler is switched off.
The circuit consist of IC1 (555 Timer IC) which is used as an astable multi
vibrator used to generate clock pulses. These are fed to decade dividers or counters
formed by IC2 and IC3 (IC CD4017B). These ICs act as divide by 10 and divide by 9
counters respectively. The values of capacitor C1 and resister R1 and R2 are adjusted so
that the final output of IC3 goes high after 8 Hours.
So during summer nights the temperature is quality high but as time passes
temperature starts dropping. So it is required to reduce the speed of a fan or cooler after
particular periods. By using this device these reducing can be done automatically. This
also makes the reduced conception of power.
BLOCK DIAGRAM DISCRIPTION
The block diagram is shown above the important parts consist of a 555 Timer IC and 1
divide by 9 and divide by 10 counter and relays. Each block in the block diagram is
explained in detail in below.
Astable Multivibrator
In this block diagram Astable multivibrator which is used as a pulse generator
circuit it’s high and low state are both unstable. It provides clock pulses for the working
of the decade counter1. The output of the multivibrator toggles with the low and high
continuously, infect generating a train of pulses.
Decade counter1
It accepts the output from the astable multivibrator as clock pulse. And the
counter starts counting when there is a output at the astable output.
Decade Counter2
It accept the output from the decade counter1 and counter start counting till
there is an output from the decade counter1 and it act as a divide by 9 counter.
Relay
This device simply acts as an electronic switch. When the output from the decade
counter 2 reaches the relay terminal it will control the speed of the fan or cooler by
switching of relays.
