Simulate PWM Using Labview Softwere

PWM

• Pulse Width Modulation (PWM) used in this process to control the speed of the motor by varying the duty cycle of the PWM. In this system, 0% duty cycle produce 0V of output voltage which means the PWM is in fully-off state while 100% duty cycle produces 5V of output voltage which means the PWM is in fully-on state.
  

• The variable output voltage which denoted here as Controlled Voltage (Vc) is used for variable input voltage to the motor which give variable speed to the motor which depends on the input voltage.

Pulse width modulation ( Final Control Element)

• Pulse width modulation (PWM) is a technique to control the DC motor speed which is a series of digital pulses is used to control an analog circuit. The length and frequency of these pulses determines the total power delivered to the circuit.  The digital pulse train that makes up a PWM signal has a fixed frequency and varies the pulse width to alter the average power of the signal. The ratio of the pulse width to the period is referred to as the duty cycle of the signal.  Figure below is the waveform of PWM in 40% until 100% of duty cycle.

Labview program

LABVIEW SOFTWARE (one of SCADA system which can monitor and controlling)

Design a circuit and program in labview

Features need to be added on the labview software:

• SET POINT (knob which control the voltage)
• DAQ ASSIST 1(acquired and transmit signal from output sensor)
• DAQ ASSIST 2 (generate voltage from DAQ card to the hardware)
• SIMULATE SIGNAL (PWM)
• WAVEFORM SENSOR
• WAVEFORM PWM
• CALCULATION
• PID (Compare and calculating the error continuously)
• CONSTANT(create value for PWM duty cycle)
• MEAN BLOCK (get the average result in order to get precise value)
• WIRING AND CONNECTION

Installation of Hardware

Step 1

Street board has been used for installing the mosfet circuit.

 

Step 2

Mosfet circuit is attached to the prospect

Step 3

Installation of dc motor 6V and Iron 88 stainless steel is used to hold the motor.

Step 4
Wiring installation for signal output from the sensor

Step 5

Sensor RE08A included with slotted disc is connected together with motor

Step 6

Complete circuit Hardware

Interface Between The DC Motor and Sensor RE08A

• Optical encoder (Speed Sensor)

Speed sensor is used to measure the speed of the DC motor. This sensor is placed at the rotation of the shaft. The connection of this sensor is shown in Figure below.

• There are plenty of speed sensors that available at the current market. For this project, Rotary Encoder Kit RE08A has been chosen because easy to use, easy to understand. This kit is made to sense the rotation of the DC motor by generating the pulses. These pulses can be translated into the speed of the DC motor by applying a simple mathematical formula which will be added into the programming part. The pulses generated by this RE08A are shown in Figure below and the formula to calculate the speed is shown in Equation below

• Figure above shows that +5 pin is connected to the +5V source. The Gnd pin is connected to the ground. The Signal pin which gives the pulses as output is connected to the counter pin at DAQ through interrupt approach. 
  

• These pulses represent the rotation of the DC motor. We have to count these pulses in one minute to get the speed in rpm. The LabView will measure the time period of the pulse signal. Then, we use the mathematical method to find frequency. 

• Frequency is multiply with 60 because 60 is assume as a 60 second or 1 minute. Then, Divide by 8 because one full rotation has 8 blades.

• Figure below shows the interface between the DC motor and the RE08A. Slotted disc has been installed at the end of DC motor shaft. The wire from DC motor is connected to the power source. In order to control the speed, an adjustable resistor has been connected to the power source which is seeks to adjust the desired speed. The value of speed will appear at the computer screen

Interface between the DC motor and RE08A

    Installation of sensor

• 
  There are 3 terminal of sensor which is 5V, ground, and signal.5V terminal is generated by function generator in the lab and the ground of sensor is connected to the DAQ ground terminal. Signal that produce from this sensor is connected to the DAQ assist means that DAQ required signal from sensor.