ECE 101 An Introduction to Information Technology Digital Sensors

1
ECE 101 An Introduction to Information
TechnologyDigital Sensors
2
Unit Prefixes
tera T 1012
giga G 109
mega M 106
kilo k 103
deci d 10-1
centi c 10-2
milli m 10-3
micro ? 10-6
nano n 10-9
pico p 10-12
3
Information Path
Source of Information
Information Display
Digital Sensor
Information Receiver and Processor
Information Processor Transmitter
Transmission Medium
4
Electric Circuit Concepts

• Charge, Q or q
• Current, I or i motion of charge (through)
• Direct current
• Alternating current
• Voltage or electric potential, V or v (across)
• Motion of charge occurs due to a force pushing on
  it
• Work per unit charge is voltage
• If current through an element results in an
  expenditure of energy, than a voltage or
  potential drop occurs
• Battery
• Power, P VI, or pvi

5
Electric Circuit Laws

• Multiple loads
• Series same current
• Parallel same voltage
• Resistance and Ohms law, vRiRR
• Kirchhoffs Laws
• Voltage law v1 v2 v3 . 0 (sum of
  voltages around a loop is zero)
• Current law i1 i2 i3 . 0 (sum of
  currents at a node is zero)

6
Mechanical Switches

• Break the flow of electrical current
• May be activated by the outside environment, such
  as, change in switch position, temperature,
  acceleration
• May be activated in series
• open no alarm
• closed alarm activated
• May be activated in parallel
• open alarm activated
• closed no alarm

7
(No Transcript)
8
(No Transcript)
9
(No Transcript)
10
Mechanical Switches

• Note the matrix arrangement for the keyboard and
  the clever scheme to minimize the number of wires
• Each key is a switch
• Reduce the number of wires by using a matrix of
  switches formed by rows and columns of keys
• Number of wires number of columns number of
  rows NW NC NR
• Number of switches, NS NC NR

11
(No Transcript)
12
Sensors or Transducers

• Front end of information (electrical) systems
• Converts physical energy into an electrical
  signal
• Produce the data to be transmitted, processed
  and/or stored
• Analog (continuous) or digital (example, a binary
  switch)
• Mechanical, optical, thermal, electrical

13
Optical sensors

• Visible UPC (universal product code) using
  lasers), IR (remote controls)
• Beam interrupt presence of light may actuate a
  switch (often mechanical)
• Digital Data transmission use of threshold
• Noise and weather (attenuation) not as
  significant
• Beam intensity not a factor (good for cellular
  telephone)

14
Optical Proximity Sensors

• Unlike beam interrupt, the the transmitter and
  receiver in the same device.
• Reading of Bar Codes, facsimile machines
• Note the clever way of reading the UPC code at an
  angle and the operation of an auto-focus camera.
  Trigonometry is key here!

15
(No Transcript)
16
Infrared (IR) Range Sensors
17
Infrared (IR) Range Sensors

• Uses variation of proximity sensor to determine
  the range of an object for setting the focus of
  an auto focus camera

transmitter
R
S
R/S f/x
f
x
receiver
S and f fixed by camera design
18
Digital IR Range Sensors
19
Digital IR Range Sensors

• Uses an array of small detector elements - no
  determinations or calculations needed

transmitter
R
S
R/S f/x
f
receiver
S and f fixed by camera design
20
Inverse Square Law

• Key law in physics, gravity, light intensity,
  Coulombs law in EM
• IP/A where A?r2, or I1/ r2
• Determines the spacing of antennas in cellular
  telephone system
• Can be used to locate a transmitting signal

21
(No Transcript)
22
Inverse Square Law
R ?Ro
R Ro
r ro
r ? ro
I (r ?ro) P/(??2r2) I (r ro) /?2
23
(No Transcript)
24
(No Transcript)
25
(No Transcript)