In this project I am going to discuss a
project in which a microcontroller, 89c52, is used to generate PWM signals.
These signals are then used to control a DC motor and hence indirectly contributes to
controlling the speed. Thus this article is all about a device for
controlling speeds of any moving object. The base of thinking behind making it is to
stop or minimize the speed of the moving object if any hindrance comes in front
of the moving object. Although the concept is not mine, it is already been
implemented in many projects, but through this article another implementation is
being discussed. Here we are using PWM waves to control speed of moving object
and for this we are using microcontroller 89c52. Although we can use any other
device as well to generate the PWM waves like 555 timer. The DC motor which is
used in the whole circuitry is actually controlled Power supply. The power can
be supplied either by battery or AC power supply can also be used. The switching
'on' and 'off' of the power causes the motor to move or change speed. What actually happens is
the DC motor starts from zero and then gradually increases its speed. When we
switch on the button the DC motor turns on and starts movement and on switching it
off, the motor stops. It depends on the time duration for which the power supply
is given to this DC motor. If the intervals of switching on and off is small,
the motor gets less time to increase its speed and hence the vehicle will move
at a slower speed. Hence it depends on the system to control the speeds. We have
divided our circuit in three major parts, IR transceiver, multivibrator circuit
and microcontroller based DC motor speed. What happens in the circuit is that the IR
sensor detects if there is any hindrance in front of the moving device.
On sensing the obstacle it activates a relay driver and with that a
multivibrator output is connected with the down speed connectivity of the
circuit. The power supply which we provide can be AC.
Now we will take a look about the circuit and its arrangement.
![sona11.bmp]()
We provide an AC power source to step down using a step down transformer.
The 230V AC is stepped down and converted into 9V with the help of this
transformer. This step down voltage is rectified by a bridge rectifier and then
this voltage is regulated by the regulator. The capacitors are used as a filter
and to bypass the DC component. We have also used LED as an indicator and its
turning on indicates that we are getting a power supply. It is to be noted that a
resistor is also connected just before the LED; this is to limit the current which
flows through it. We have also used a diode so as to make a drop of about 0.4V
in voltage. Now you must be thinking that out of 9V we are getting only 5.4 of
total voltage; actually to drive our motor and for proper functioning we need
only this much of voltage as it satisfies our specifications. Microcontroller
89c52 is used to generate PWM waves; therefore out of 9V from the step
down transformer, nearly 3V has been consumed by the bridge rectifier and regulator.
And then the diode made some drop and then out of 6v we finally got 5.4v of
voltage which is then used by te DC motor for proper functioning.
The microcontroller 89c52 is actually a low power, CMOS 8-bit microcontroller
with 8Kb of flash memory which can be programmed as much as we want to. The
working of the DC motor is based on the PWM waves. The advantage with the system is
that DC motor's speed decreases when it gets the directions from the relay and
then according to those directions the PWM signals are generated. On removal of
that hindrance the sensor again detects the position of that obstacle and then
sends the signals according to which PWM waves generated which increases the
speed of the DC motor. The resistors preferred here are carbon resistors. We have
used a seven segment display to show the speed of vehicle in the form of digits,
it actually displays one tenth value of the duty-cycle. Duty cycle is a very
important factor, it is a measurement of power given by any emitter or something
may be a radar. It tells us that out of the total time, for how much time our
device is on. Like if a motor is on twice in 60 seconds. Then its duty cycle
would be 2/60 i.e.,1/30.
Conclusion : This is a very simple and economic
implementation of some hardware devices which can be used with the help of some
general logics. The above implementation shows the use of simple
combinations of some hardware components. which is resulted into a useful
implementation. This device can be used in our automobile engines which can help
in reducing accidents. This can be very effective and more useful if some extra
work in some on this field.
Resources:
Microcontroller 89c51 used in robotics
Microcontrollers for robotics