PWM DC Motor Speed Control
Laboratory Final Design Project PWM DC Motor Speed Control
Bowen Wang, Siyang Xia, Renhao Xie, E E 331 Lab, Winter 2013
TABLE OF CONTENTS
Purpose of project, features, ratings …………………….…………3 Block diagram …………………………………...………..…………….…… 4 Complete schematic ………….……………………..………………………5
Circuit simulation…………………………… ……...……… ……..….….. 6 Test results…………………………… ……...…………..…… ………...….. 7 Bill of materials and Cost estimate ……...……….… ……….….. 11
Summary/Conclusion……………………….…………………….…… 11
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1.Purpose of project, features, ratings
1.1 Purpose: It is important for engineers to control a higher power load with a lower power circuit. However, if we perform a direct modulation, it will create a rather inefficient design with the control device (transistor). Thus a better way with a high power efficiency is to rapidly switch the control device on and off at a frequency which is high enough that the load effectively sees only the average over many cycles. And this is also the basic idea of this project. The purpose of this design project is to develop and prototype a high efficiency pulse width modulation (PWM) speed control for a small DC motor. 1.2 Features: VDD power supply (5V and 15V) Resistor: 1k, 100k, potentiometer (maximum 10k) Zener Diode: 1N4007 Capacitor: 100nF, 47nF NMOS: 2N7000 LM555 timer: LM555CN Comparator: LM339N Motor Jump wires Breadboards 1.3 Ratings Input Voltage: 5V for the chips, 15V for the motor Output voltage: triangle wave 0-‐3V for the saw tooth, square wave 0-‐5V for the motor
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Block diagram
Figure 2.1 Block Diagram of the PWM DC motor speed control There are four parts for the whole system: oscillator, PWM modulator, motor driver and the DC motor. The oscillator will create a triangle saw tooth waveform drive the motor control circuit. We build this by powering a 555-‐timer chip with 5 volt DC Source, which will create a linear waveform with a 10kHz frequency. And this signal will be sent to the next part: the pulse width modulation (PWM). In this part, we setup a control voltage input and compares it to the saw tooth wave, and get an output of a square-‐pulse wave. Then the square wave is sent to the motor driver that is comprised of a buffered transistor. The pulse is turning the switch on and off rapidly to keep the motor running while conserving power. In the end, we power the motor by a 15-‐volt DC source and the whole system works.
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Complete schematic (Circuit Design)
Figure 3.1 Schematic Diagram of the whole system Figure 3.1 shows a complete schematic diagram of the whole system. The left part is oscillator, the up part is PWM, the right part is the motor driver and finally the big 3-‐ D motor is in the middle. In order to build exact the same circuit, we buy some new components from the E E store beside the given lab kit. First for the oscillator, we setup the power-‐supply to 5V which is V1. And we use the 100k-‐ohm resistor for R1 and R3, and connect 2 100k-‐ohm resistors in series, which is 200k ohm for R3. Also we connect 100nF and 47nF in parallel, which is 147 nF for C1. And we buy the LM555CN chip for U1 and connect the circuit as shown above. Then for the comparator (PWM), we bought the LM339 chip from the E E store, and use the same power supply (V1) as for the oscillator. Also we use the 1k-‐ohm resistor for R4 and the potentiometer for X1. Then we connect the circuit as shown above. Then for the motor driver, we bought the diode 1N4007GP and the transistor 2N7000 from the E E store, and connect them as the circuit shown above. Finally for the motor, we bought it from the E E store and power it by a 15-‐volt power supply, and then connect it as the circuit shown above.
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Circuit simulation
Figure 4.1 Simulation of the oscillator and the PWM
Parameter Power Supply Oscillator PWM modulator
Design Specification +5V for speed control +15V for motor 10KHz +/-‐5% frequency
Test Results 5.0V 15.0V 9.7KHz, which is 3% lower than 10KHz, within the 5% range. Saw tooth asymmetrical Yes, it’s saw tooth ramp asymmetrical ramp
Bowen Wang, Siyang Xia, Renhao Xie, E E 331 Lab, Winter 2013
TABLE OF CONTENTS
Purpose of project, features, ratings …………………….…………3 Block diagram …………………………………...………..…………….…… 4 Complete schematic ………….……………………..………………………5
Circuit simulation…………………………… ……...……… ……..….….. 6 Test results…………………………… ……...…………..…… ………...….. 7 Bill of materials and Cost estimate ……...……….… ……….….. 11
Summary/Conclusion……………………….…………………….…… 11
2
1.Purpose of project, features, ratings
1.1 Purpose: It is important for engineers to control a higher power load with a lower power circuit. However, if we perform a direct modulation, it will create a rather inefficient design with the control device (transistor). Thus a better way with a high power efficiency is to rapidly switch the control device on and off at a frequency which is high enough that the load effectively sees only the average over many cycles. And this is also the basic idea of this project. The purpose of this design project is to develop and prototype a high efficiency pulse width modulation (PWM) speed control for a small DC motor. 1.2 Features: VDD power supply (5V and 15V) Resistor: 1k, 100k, potentiometer (maximum 10k) Zener Diode: 1N4007 Capacitor: 100nF, 47nF NMOS: 2N7000 LM555 timer: LM555CN Comparator: LM339N Motor Jump wires Breadboards 1.3 Ratings Input Voltage: 5V for the chips, 15V for the motor Output voltage: triangle wave 0-‐3V for the saw tooth, square wave 0-‐5V for the motor
3
Block diagram
Figure 2.1 Block Diagram of the PWM DC motor speed control There are four parts for the whole system: oscillator, PWM modulator, motor driver and the DC motor. The oscillator will create a triangle saw tooth waveform drive the motor control circuit. We build this by powering a 555-‐timer chip with 5 volt DC Source, which will create a linear waveform with a 10kHz frequency. And this signal will be sent to the next part: the pulse width modulation (PWM). In this part, we setup a control voltage input and compares it to the saw tooth wave, and get an output of a square-‐pulse wave. Then the square wave is sent to the motor driver that is comprised of a buffered transistor. The pulse is turning the switch on and off rapidly to keep the motor running while conserving power. In the end, we power the motor by a 15-‐volt DC source and the whole system works.
4
Complete schematic (Circuit Design)
Figure 3.1 Schematic Diagram of the whole system Figure 3.1 shows a complete schematic diagram of the whole system. The left part is oscillator, the up part is PWM, the right part is the motor driver and finally the big 3-‐ D motor is in the middle. In order to build exact the same circuit, we buy some new components from the E E store beside the given lab kit. First for the oscillator, we setup the power-‐supply to 5V which is V1. And we use the 100k-‐ohm resistor for R1 and R3, and connect 2 100k-‐ohm resistors in series, which is 200k ohm for R3. Also we connect 100nF and 47nF in parallel, which is 147 nF for C1. And we buy the LM555CN chip for U1 and connect the circuit as shown above. Then for the comparator (PWM), we bought the LM339 chip from the E E store, and use the same power supply (V1) as for the oscillator. Also we use the 1k-‐ohm resistor for R4 and the potentiometer for X1. Then we connect the circuit as shown above. Then for the motor driver, we bought the diode 1N4007GP and the transistor 2N7000 from the E E store, and connect them as the circuit shown above. Finally for the motor, we bought it from the E E store and power it by a 15-‐volt power supply, and then connect it as the circuit shown above.
5
Circuit simulation
Figure 4.1 Simulation of the oscillator and the PWM
Parameter Power Supply Oscillator PWM modulator
Design Specification +5V for speed control +15V for motor 10KHz +/-‐5% frequency
Test Results 5.0V 15.0V 9.7KHz, which is 3% lower than 10KHz, within the 5% range. Saw tooth asymmetrical Yes, it’s saw tooth ramp asymmetrical ramp
