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DIGITAL CONTROLLER DESIGN
Lab Report-02 (15-02-2014)
Arun Rahul S
Sr No: 10578
Open Loop Speed Control of DC Motor
Circuit Diagram
Vdc
F.D
Va eb
eb
ATMEGA 328p
POT
R sense
Controller
ADC
PWM
Gate driver
D
DC motor
Ia sense
Q
Eb sense
Duty cycle adjustment Fig (1).DC motor speed control experimental setup.
The duty cycle is controlled by varying the duty cycle adjustment pot.
Ratings and specification
Vdc
: 24.4 V
PMDC Motor/Generator Rated speed
: 24 V
PMDC Motor/Generator Rated speed
: 1770 RPM
PMDC Motor/Generator rated current : 5A.
MOSFET
: IRF640.
Freewheeling diode
: IRF640 body diode.
R sense
: 0.6Ω
Current sensing
: Opamp LM324 based instrumentation amplifier.
Voltage sensing
: Opamp LM324 based Differential amplifier.
Gate driver
: Complementary transistor with optocoupler isolation.
Controller
: ATMEGA 328P
PMDC motor equivalent circuit ia La
Ra
Va
J
Tem
Permanent magnet eb
w b TL
Fig(2). PMDC motor equivalent circuit diagram.
Dynamic equations for DC motor is given by,
=
+
+
= ф
(1)
(2)
= ф
−
(3)
=
ф=
=
+
(4)
(5)
At steady state
=
=
+
∗
=
At no load condition
(7)
∗
−
(6)
=
(8)
(9)
=0
∗
=
(10)
Current sensing
Fig(3) current sensing circuit
Current scale
I=1.33A then I_sence=1 V
Voltage sensing
Fig(4) voltage sensing circuit
Vin=30V then V_sence=5V
MOSFET gate driver circuit
Fig(5) gate driver circuit.
PMDC motor/generator Speed Vs back emf characteristics
For a PMDC motor back emf is directly proportional to the speed since field is constant. According to equation
=
∗ , Where Km is the back emf constant.
For the experiment PMDC motor/generator set is configured according to circuit diagram and PWM duty cycle is varied from low value of around 15% to 90% using a potentiometer. The ADC senses the
Lab Report-02 (15-02-2014)
Arun Rahul S
Sr No: 10578
Open Loop Speed Control of DC Motor
Circuit Diagram
Vdc
F.D
Va eb
eb
ATMEGA 328p
POT
R sense
Controller
ADC
PWM
Gate driver
D
DC motor
Ia sense
Q
Eb sense
Duty cycle adjustment Fig (1).DC motor speed control experimental setup.
The duty cycle is controlled by varying the duty cycle adjustment pot.
Ratings and specification
Vdc
: 24.4 V
PMDC Motor/Generator Rated speed
: 24 V
PMDC Motor/Generator Rated speed
: 1770 RPM
PMDC Motor/Generator rated current : 5A.
MOSFET
: IRF640.
Freewheeling diode
: IRF640 body diode.
R sense
: 0.6Ω
Current sensing
: Opamp LM324 based instrumentation amplifier.
Voltage sensing
: Opamp LM324 based Differential amplifier.
Gate driver
: Complementary transistor with optocoupler isolation.
Controller
: ATMEGA 328P
PMDC motor equivalent circuit ia La
Ra
Va
J
Tem
Permanent magnet eb
w b TL
Fig(2). PMDC motor equivalent circuit diagram.
Dynamic equations for DC motor is given by,
=
+
+
= ф
(1)
(2)
= ф
−
(3)
=
ф=
=
+
(4)
(5)
At steady state
=
=
+
∗
=
At no load condition
(7)
∗
−
(6)
=
(8)
(9)
=0
∗
=
(10)
Current sensing
Fig(3) current sensing circuit
Current scale
I=1.33A then I_sence=1 V
Voltage sensing
Fig(4) voltage sensing circuit
Vin=30V then V_sence=5V
MOSFET gate driver circuit
Fig(5) gate driver circuit.
PMDC motor/generator Speed Vs back emf characteristics
For a PMDC motor back emf is directly proportional to the speed since field is constant. According to equation
=
∗ , Where Km is the back emf constant.
For the experiment PMDC motor/generator set is configured according to circuit diagram and PWM duty cycle is varied from low value of around 15% to 90% using a potentiometer. The ADC senses the