The modulation is a process of varying the parameter of a carrier signal in accordance with the instantaneous value of the message signal. Modulation technique is used to encode the message into a pulsing signal.
A Pulse Width Modulation (PWM) Signal is a method for generating an analog signal using a digital source. A PWM signal consists of two main components that define its behavior- a duty cycle and a frequency. The duty cycle describes the amount of time the signal is in a high (on) state as a percentage of the total time of it takes to complete one cycle. The frequency determines how fast the PWM completes a cycle (i.e. 1000 Hz would be 1000 cycles per second), and therefore how fast it switches between high and low states. By cycling a digital signal off and on at a fast enough rate, and with a certain duty cycle, the output will appear to behave like a constant voltage analog signal when providing power to devices.
• The term duty cycle describes the proportion of 'on' time to the regular interval or 'period' of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on.
The PWM method is a great method to control the amount of power delivered to a load without initiating the waste power.
• Average Output Voltage is Porportional to ON Time Of Duty Cycle.
PWM signals are used for a wide variety of control applications. Their main use is for controlling DC motors but it can also be used to control valves, pumps, hydraulics, and other mechanical parts. The frequency that the PWM signal needs to be set at will be dependent on the application and the response time of the system that is being powered. Below are a few applications and some typical minimum PWM frequencies required:
The following are the advantages and disadvantages of controlling the speed of a DC motor with PWM are
By This Method Smoothly Controlled The Speed Of DC Motor At Negligible Noise
BY using This Circuit You can control the speed of DC Fan by tuning the (Potentiometer) volume control variable resistance. These circuits are based on 555 Timer .
Components of circuit 1
• IC 555-1
0.01uf (100) -1
Preset (VR)- 500KΩ-1
• DC Motor
Video OF DC Motor/FAN Speed Regulator (circuit 1)