Sensors Lecture 4

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SensorsLecture 4
DE1 AUE 2007 Bo Rohde Pedersen
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Today
Inspiration for projects Sensors Useful Components
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Temperature NTC and PTC
Negative Temperature Coefficient Is a resistor
with a large negative temperature
coefficient Positive Temperature
Coefficient Is a resistor with a large negative
temperature coefficient Made of Carbon,
Iron, Silicon. Linearity Nonlinear function
between resistance and temperature
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Temperature Integrated Sensor
Inside of an intergraded device
The aim is to make a linier devise which in our
case is easy to use. In this case is the
temperature measurement device based on Silicon.
Remember to check manufactory specification for
setup and use
Example National LM34
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Flex Sensors/Bend Sensor
Flex Sensor Is a resistor that changes the
ohmic value when it gets krumt. Made
of Resistive Carbon technology, silver. Typical
range 10-80kOhm
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Strain Gages
Piezoresistive Element Resistance change takes
place when length or area are changed. Made
of Wire, metal foil or semiconductor. Linearity
Nearly linear function between resistance and
force
Sensitivity
One direction
Two direction
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Photoconductive Cell (Photocell)
Photoresistor Is a resistor that changes the
ohmic value depending of the light
intensity LDR Light Depending Resistor Made
of Cadmium sulfide (CdS), Cadmium selenide
(CdSe). Typical range 100-10,000 Ohm
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Photo Diode
Photo Diode When a current is flowing thru it
will behave as a voltage source depending of
the light. The Principe is the photovoltaic, as
it is used in solar cells. Made of Silicon.
(Semiconductor) Linearity Good in a relative
large range. Low noise
NB Also available as a transistor. A transistor
is a semiconductor we later will work with.
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Switch- and Reflector Module in Use
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Tilt Sensor
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Electrical Set Up of Tilt Sensor
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Piezo Sensor

• Generates a Voltage
• High impedance app 1Mohm (1.000.000)
• Mechanically tough

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Applications
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Passive Inferred Sensor Movement
The device is measuring the temperature or the
change in temperature
Device
Detection Anglers
Connect GND to 0V and V to 5V. O/P connect to
digital in.
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Passive Infrared Sensor Driver Chip
KC778B is the main chip on the passive infrared
sensor. Here are the features of the passive
infrared sensor
-Daylight adjusting -Filtering noise -Drivers for
sensor
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Long Distance Measurement Sensor
The device sends out infrared light and detects
the reflections
Device
Block diagram
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Principles of IR Distance Measurement
Triangulating principle Light is sent out at a
known angle from the transmitter and the receiver
detects the direction of the light that is
received (angle). Based on the receiving angle
the distance is calculated. The triangulating
principle is used for the short distance
measurements in the range (um/mm) with high
resolution.
Time of flight principle In the principle Time of
flight is a short pulse of light sent out. This
pulse is reflected and the time from the pulse
being sent out till it is received again is
measured. This time is corresponding to the
distance.
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Output Signals
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Measurement Spread
Not the IR sensor we have!!
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Zener Diode
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Transistors
Basic component inside
Water systems
Electrical diagram
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Examples of Useful Transistor

• Classic transistors
• BC547 NPN max 100mA
• BC557 PNP max 100mA
• BD136 NPN max 1A
• BD137 PNP max 1A
• 2N3055 NPN max 10A

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