Download Introduction to Basic Electronic Components

Basic Electronics and the Design of a
Roller-coaster G-Meter
Goal - To provide an introduction to basic electronic components
and to apply this knowledge to the design of a roller-coaster Gmeter.
• Problem Definition
• Describe the characteristics of basic electronic components
• Analyze a schematic to see how it meets design goals
Basic Electronics and the Design of a
Roller-coaster G-Meter
Design Requirements
• Sense acceleration in 2 axis
• Record peak values
• Store multiple measurements
• Battery powered
• Small enough to fit in a pocket
• 0.1G resolution
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
We will discuss:
• Resistors
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•
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•
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Capacitors
Inductors
Diodes
Transistors
Op-amps
Microcontrollers
How to apply these components
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Resistors
A resistor is a two-terminal electrical component that resists the flow
of current, producing a voltage drop between its terminals in
accordance with Ohm’s Law. The standard unit of resistance is the
Ohm (W).
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Resistors
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Resistors
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Resistors
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Resistors
Voltage Divider
Vi = 5V
R1 = 10K
R2 = 20K
20000
Vo = 5 *
10000 + 20000
Vo = 3.33V
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Inductors
An inductor is a passive electrical device that stores energy in a
magnetic field, typically by combining the effects of many loops of
electric current.
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Inductors
Inductance, measured in henrys (H) is an effect which results from
the magnetic field that forms around a current carrying conductor.
Current in an inductor tends to remain constant regardless of voltages
applied to the inductor.
Inductance can be increased by looping the conductor into a coil
which causes magnetic flux from adjacent loops of the conductor to
link.
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Inductors
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Inductors
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Capacitors
A capacitor is a device that stores energy in the electric field
created between a pair of conductors on which equal but opposite
electric charges have been placed. Capacitance is measured in
Farads or micro Farads (uF)
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Capacitors
A capacitor consists of two electrodes or plates, each of which stores
an opposite charge. These two plates are conductive and are separated
by an insulator or dielectric.
The voltage across a capacitor tends to remain constant.
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Capacitors
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Capacitors
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Passive Filters
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Introduction to Basic Electronic Components
Diodes
A diode can be thought of as the electronic version of a check valve.
By restricting the direction of movement of charge carriers, it allows
an electric current to flow in one direction, but essentially blocks it in
the opposite direction. Diodes may be made from semiconductor
materials such as silicon or germanium or may be fabricated using
devices depending on thermionic emission (vacuum tube).
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Diodes
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Diodes
Half-Wave Rectifier
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Transistors
The transistor is a solid state semiconductor device which can be
used for amplification, switching, voltage regulation, signal
modulation and many other functions. It acts as a variable valve
which, based on its input voltage, controls the current drawn by it
from a connected voltage supply.
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Transistors
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Transistors
Vin = 5V
Vf = 1.2V
Vcc = 12V
RC = 1K
RB = 10K
Vin - 0.7 = 5 - 0.7 = 430uA
IB =
RB
10000
Vcc - 0.25 - 1.2 12 - 0.25 - 1.2
=
IC =
RC
1000
IC = 10.6mA
.0106
IC
Gain =
= .00043 = 24.7
IB
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Op-amp
An operational amplifier or op-amp is a very high-gain amplifier
which has two inputs, one inverting (−) and one non-inverting (+).
The output voltage is the difference between the + and − inputs,
multiplied by the open-loop gain. Because the op-amp has such high
gain, the behavior of the amplifier is almost completely determined by
the external elements.
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Introduction to Basic Electronic Components
Internal Structure of an Op-amp
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Introduction to Basic Electronic Components
Op-amp
Vout = G*(V+ - V-)
Vs- < Vout < Vs+
Three assumptions of an ideal Op-amp operating in the linear range:
1) V+ = V2) G = Infinite (or close to it)
3) The current into the V+ and V- terminals is zero
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Op-amps
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Op-amps
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Op-amps
#1501 Team THRUST 2005
Introduction to Basic Electronic Components
Microcontrollers
A microcontroller is a “computer-on-a-chip” used to control
electronic devices. It is a type of microprocessor emphasizing selfsufficiency and cost-effectiveness, in contrast to a general-purpose
microprocessor, the kind used in a PC. A typical microcontroller
contains all the memory and I/O interfaces needed, whereas a general
purpose microprocessor requires additional chips to provide these
necessary functions.
There are many manufacturers of microcontrollers that make a wide
range of devices. Virtually all combinations of memory size, I/O
count, peripheral set and package style are available.
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Design of a G-Meter
Design Requirements
• Sense acceleration in 2 axis
• Record peak values
• Store multiple measurements
• Battery powered
• Small enough to fit in a pocket
• 0.1G resolution
#1501 Team THRUST 2005
Design of a G-Meter
Power Supply
• Switching buck regulator is used for conversion efficiency
• SW1 chops the DC input voltage - output voltage is
determined by the duty cycle of the chopped waveform
• L1 and C1 form a 2nd order low pass filter that filters the chopped
waveform to a DC voltage.
• D1 is a flyback diode that allows current to flow when SW1 is open.
#1501 Team THRUST 2005
Design of a G-Meter
Power Supply
• Powered by a 9V battery
• Switching buck regulator for efficiency
• C1 supplies large current pulses to regulator input
• LM2574 chops the DC input voltage - output voltage is
determined by the duty cycle of the chopped waveform
• L1, C2 and C3 form a 2nd order low pass filter that filters the chopped
waveform to a DC voltage.
• D1 is a flyback diode that allows current to flow when the regulator switch is
open.
#1501 Team THRUST 2005
Design of a G-Meter
Microcontroller
Basic circuit to make micro run:
• 4MHz Oscillator - X2, C6, C7
• Reset circuit - R7
• Power supply de-coupling
capacitor - CU4
#1501 Team THRUST 2005
Design of a G-Meter
Input Switches
• Micro inputs are normally pulled
high with resistors R4 - R6
• When SW2, SW3 or SW4 are
pressed, the corresponding micro
input is pulled low.
Select - Selects the data location to store
the next measurement
Start - Starts recording data
View - Puts the micro in view mode to
look at stored data.
#1501 Team THRUST 2005
Design of a G-Meter
Display
• A second micro is used as a display driver. Specialized driver ICs
exist for different types of displays - LCD, OLED, etc…
• Two LEDs are used to indicate when the readings are negative.
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Design of a G-Meter
Serial Bus
A serial data bus is used
to connect the main micro
and the display micro.
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Design of a G-Meter
Analog to Digital Converter
• An A-D converter converts an analog signal into discrete digital
numbers - typically with 8 to 16 bits of resolution.
• For example - The output of an 8-bit A-D with a 3V input and a 5V full scale
reading would be:
3V
* 28 = 154 decimal = 9A hex = 10011010 binary
5V
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Design of a G-Meter
Sensor and Signal
Conditioning
• Output of ADXL250 accelerometer is amplified by U10A and U10B
• C8/R10 and C9/R11 form low pass filters that reduce the noise on
the sensor output
#1501 Team THRUST 2005
Design of a G-Meter
Additional Memory
• An optional external memory
chip was added for future
expansion
• EEPROM (Electrically Erasable
Programmable Read Only
Memory)
• Rather than only recording the
peak accelerations, data can be
recorded every 1/4 second
#1501 Team THRUST 2005
Design of a G-Meter
Complete Schematic
#1501 Team THRUST 2005
Design of a G-Meter
…And now the real question: How many G’s do they pull?
Lateral G’s
Millennium Force
1.4
Raptor
1.8
Magnum
1.3
Power Tower (Up)
0.4
Vertical G’s
4.5
4.1
3.9
2.6
#1501 Team THRUST 2005
References
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Resistors - http://en.wikipedia.org/wiki/Resistor
Capacitors - http://en.wikipedia.org/wiki/Capacitor
Inductors - http://en.wikipedia.org/wiki/Inductor
Diodes - http://en.wikipedia.org/wiki/Diode
Transistors - http://en.wikipedia.org/wiki/Transistor
Op-amps - http://en.wikipedia.org/wiki/Op-amp
Microcontrollers - http://en.wikipedia.org/wiki/Microcontroller
#1501 Team THRUST 2005