uvm cricketsat wireless sensor. remote temperature measurement possible application –measure...
Post on 22-Dec-2015
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![Page 1: UVM CricketSat Wireless Sensor. Remote Temperature Measurement Possible Application –Measure temperature in the upper atmosphere –10 km altitude Two challenges:](https://reader036.vdocument.in/reader036/viewer/2022062516/56649d795503460f94a5bdf5/html5/thumbnails/1.jpg)
UVM CricketSat Wireless Sensor
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Remote Temperature Measurement
• Possible Application
– Measure temperature in the upper atmosphere
– 10 km altitude
• Two challenges:
– Measure temperature indirectly
– Long-range wireless transmission of data
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Thermistor Temperature Sensor• Resistance changes with
temperature• Problem: Resistance
cannot be measured directly
• Requires additional circuitry to produce an electrical response
• Oscillator circuit is the simplest and lowest cost solution
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• Produces an oscillation that changes with temperature
• Circuit based on the popular 555-Timer IC
• Frequency determined by two resistors and a capacitor
• Resistive and capacitive type sensors may be substituted
• In our case, the upper resistor is replaced with a thermistor
Temperature Sensitive Oscillator
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555-Timer Oscillator Demo
Click on picture for online demo
![Page 6: UVM CricketSat Wireless Sensor. Remote Temperature Measurement Possible Application –Measure temperature in the upper atmosphere –10 km altitude Two challenges:](https://reader036.vdocument.in/reader036/viewer/2022062516/56649d795503460f94a5bdf5/html5/thumbnails/6.jpg)
Frequency vs Temperature
• Thermistor resistance increases with colder temperature, reducing charging current
• Charging time increases, reducing the frequency
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The Wireless Connection
• Timer output signal enables transmitter during charging interval of the timing cycle
• Oscillator frequency is mixed with RF carrier frequency• Antenna is sized for carrier frequency -> short
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Receiving Station
• Receiver extracts oscillator frequency
• Frequency measured by instrument or software
• Calibration charts used to determine temperature
CricketSat Sensor
•Oscillator frequency determined by temperature
•Oscillator output signal modulates RF carrier frequency
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C1 C3C2C4 C5 C6
U2R1
D1DIP
Socket
Notch
U1: 555 Timer
IC
Dimple
Pin 1
Flat Side Up
1 2 31 2 3 4
8765
1234
U3: RF Transmitter
5-Volt Regulator
10K Ohm Thermistor
Printed Circuit Board (PCB)
47 micro-Farad Electrolytic Capacitors
Longer Lead
+ - + - + -
Longer Lead+-
Light Emitting
Diode (LED)
0.1 micro-Farad Capacitors
+-
Black Band D1 - Diode
+-
B1: 9-Volt Battery
Pins: Pins:
Antenna Wires
Battery Snap Connector
+
-
Red Lead is Positive
R4: 100 Ohm
R2: 3300 Ohm
R3: 680 Ohm
Brown-Black-Brown-Gold
Orange-Orange-Orange-Gold
Blue-Gray-Brown-Gold
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Completed CricketSat
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Prototype Development
Area
Thermistor
Test Points
Dipole Antenna
RF Transmitter
Module
Timing Capacitor
5-Volt Regulator
IC
555 Timer
IC
Flashing LED
9-Volt Battery Leads
Timing Resistor
Primary Features
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Output Jack
Noise Decoupling Capacitor
Series Isolation Resistor
Current Limiting Resistor (LED)
Noise Decoupling Capacitor
Protection Diode (Reverse Battery
Connection)
Noise Decoupling Capacitors
Secondary Features