SPEED CONTROL OF DC MOTOR
It is a simple circuit with the help of which you can control the speed of DC motor. You can also use it control the speed of windscreen wipers
used in automobiles or it can be used in toys. Easy to install because
of less components used and works well on wide range of power supply
from 5V to 12V.
Description
This circuit to control speed of dc motor is based on single IC that is NE555
which work as a-stable multi-vibrator. In this mode 555 timer is not
stable and its output is continuously changes from low to high or from
high to low. This continuous change from one state to another (high to
low and then back to original state) produces a continuous square wave
output. Now
if the power supply is first connected to a-stable circuit then
initially the timing capacitor C1 is discharged. The voltage at pin2 is
0V and the output of timer is driven HIGH. Now C1 starts charging
through VR1 and R2. Capacitor C1 is also connected to pin6 which is
threshold input of the timer.When
the voltage through C1 goes below 1/3 of the power supply, the output
of the lower comparator reaches a new value. This doesn’t change the
logic state of the flip flop which means that the output remain low. The
second comparator’s input get the voltage from pin 6 which is threshold
input and 2/3 Vcc from internal voltage divider. When the voltage
through C1 goes below 2/3 of the power supply the output of the second
comparator reaches a new level. The flip-flop changes their state and
the output becomes HIGH. So the output of 555 timer goes from HIGH to
LOW.
In this circuit we vary the speed of DC motor
with the help of VR1. When wiper arm of variable resistor is on top
position, capacitor C1 charges though R1 and D1 and produces a pulse at
the output pin 3 of long negative and short positive pulse width.
Therefore at this time speed of motor is slow and when wiper is bottom
position speed of motor is high. This output is provides to pin 3 and
the motor connected to vary its speed.
SEE THE VIDEO TUTORIAL FOR IT: VIDEO IS HERE
SEE THE VIDEO TUTORIAL FOR IT: VIDEO IS HERE
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