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very similar to the transmitters found in a garage door opener. The TX433 is perfect for this application
because it is small, light weight, inexpensive and simple to use.
Only 4 pins are required for operation of the transmitter. The square wave tone output from the 555 timer
is inputted into pin 2 (i.e., data in) of the transmitter. Pin 1 and 4 provide the transmitter with connections
for connecting a small antenna. Finally, a VCC power supply ranging from 2 to 12VDC is applied to pin
3 to provide operation power to the transmitter.
5.1.4 Summary
The CricketSat flight unit is a design that is quite simple and contains only three main components. The
components include a temperature sensor that is a NTC thermistor, an astable multivibrator that generate
the audio tone, and a transmitter. A schematic of the CricketSat flight unit is shown in Figure 22. An
assembled CricketSat flight unit that was used in the SimSat-1B test flight is shown in Figure 23.
Figure 22: CricketSat Flight Unit Schematic
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