Raspberry Pi Exam 1 UPDATED ACTUAL Exam Questions and
CORRECT Answers
What's Headless mode? - Raspberry Pi is typically used in environments where attaching a
display, keyboard, mouse, etc., is not feasible due to environment factors, cost and not required
by applications software .
Operating a Raspberry Pi by directly accessing the OS terminal or the Desktop via VNC over the
network (WiFi or Ethernet) without the need for a monitor, keyboard or a mouse is called
Headless mode.
Duty Cycle - T = 1/f
DC = Pulse Width/T
Duty cycle is the proportion of time during which a component, device, or system is operated. In
electronics, duty cycle is the percentage of the ratio of pulse duration, or pulse width (PW) to the
total period (T) of the waveform
How does a DC motor work? - A DC Motor consists of an armature (rotating part) a field. The
field can consists of either a winding (electromagnet) or permanent magnet.
(Small DC motors have permanent magnets as the field while large DC motors have windings
that forms an electromagnet.) Speed is varied by varying the magnetic field intensity of the field.
Rotational Direction can be changed by reversing the polarity of the voltage applied to the
armature.
What is an H-bridge and how does it function? - An H-bridge is built of four switches that
control the flow of current to a load. An H bridge is an electronic circuit that enables a voltage to
be applied across a load in opposite direction. These circuits are often used in robotics and other
applications to allow DC motors to run forwards or backwards. For our DC motor we use a
SN754410 which is a Quadruple Half-H-Bridge capable of controlling the rotational direction of
two DC motors.
, How does an H-bridge revers polarity? - Enable where you want the magnets to pull from to fine
tune where you want the motor to turn.
What is a Servo Motor? - Servomotor is a DC or AC Motor with a potentiometer, gear assembly
and a controlling circuit. Gear assembly is used to reduce the speed and increase the torque.
(Servomotors are rated in kg/cm. The ratings indicate how much weight a servomotor can lift at a
particular distance.
For example a servomotor rated at 6kg/cm can lift a weight of 6 kg at a distance of 1 cm
Increase in distance will reduce the weight that can be lifted.
Sg90, the motor we use, is rated at 9g/cm.)
How to use Servo Motor - All Servomotors are equipped with three wires.
Two wires are used for supply, brown is negative and red is positive.
The third wire, orange, is used for the signal that is sent from the Motor Control Unit(MCU)
which in our case will be RPi.
Servo motor angle of rotation is controlled by the duration of the applied pulse to its control pin.
Servo motor is controlled using Pulse Width Modulation (PWM) technique.
What is an Analog Signal? - Analog Signals are continuous signals that typically represent
measurement of some physical phenomenon. They use a continuous range of values to represent
information.
What is a Discrete Digital Signal - Discrete digital signal is a signal sampled at discrete instants
in time and quantized to discrete values of voltage, or current.
Nyquist's sampling theorem - The sampling frequency must be at least twice the highest
frequency component present in the analog signal.
CORRECT Answers
What's Headless mode? - Raspberry Pi is typically used in environments where attaching a
display, keyboard, mouse, etc., is not feasible due to environment factors, cost and not required
by applications software .
Operating a Raspberry Pi by directly accessing the OS terminal or the Desktop via VNC over the
network (WiFi or Ethernet) without the need for a monitor, keyboard or a mouse is called
Headless mode.
Duty Cycle - T = 1/f
DC = Pulse Width/T
Duty cycle is the proportion of time during which a component, device, or system is operated. In
electronics, duty cycle is the percentage of the ratio of pulse duration, or pulse width (PW) to the
total period (T) of the waveform
How does a DC motor work? - A DC Motor consists of an armature (rotating part) a field. The
field can consists of either a winding (electromagnet) or permanent magnet.
(Small DC motors have permanent magnets as the field while large DC motors have windings
that forms an electromagnet.) Speed is varied by varying the magnetic field intensity of the field.
Rotational Direction can be changed by reversing the polarity of the voltage applied to the
armature.
What is an H-bridge and how does it function? - An H-bridge is built of four switches that
control the flow of current to a load. An H bridge is an electronic circuit that enables a voltage to
be applied across a load in opposite direction. These circuits are often used in robotics and other
applications to allow DC motors to run forwards or backwards. For our DC motor we use a
SN754410 which is a Quadruple Half-H-Bridge capable of controlling the rotational direction of
two DC motors.
, How does an H-bridge revers polarity? - Enable where you want the magnets to pull from to fine
tune where you want the motor to turn.
What is a Servo Motor? - Servomotor is a DC or AC Motor with a potentiometer, gear assembly
and a controlling circuit. Gear assembly is used to reduce the speed and increase the torque.
(Servomotors are rated in kg/cm. The ratings indicate how much weight a servomotor can lift at a
particular distance.
For example a servomotor rated at 6kg/cm can lift a weight of 6 kg at a distance of 1 cm
Increase in distance will reduce the weight that can be lifted.
Sg90, the motor we use, is rated at 9g/cm.)
How to use Servo Motor - All Servomotors are equipped with three wires.
Two wires are used for supply, brown is negative and red is positive.
The third wire, orange, is used for the signal that is sent from the Motor Control Unit(MCU)
which in our case will be RPi.
Servo motor angle of rotation is controlled by the duration of the applied pulse to its control pin.
Servo motor is controlled using Pulse Width Modulation (PWM) technique.
What is an Analog Signal? - Analog Signals are continuous signals that typically represent
measurement of some physical phenomenon. They use a continuous range of values to represent
information.
What is a Discrete Digital Signal - Discrete digital signal is a signal sampled at discrete instants
in time and quantized to discrete values of voltage, or current.
Nyquist's sampling theorem - The sampling frequency must be at least twice the highest
frequency component present in the analog signal.
