Telemetering Beacon For VUSAT

Posted on Feb 5, 2014

The beacon controller is intended to be operated for telemetering data available on board of the VUSAT in Morse code so that the ham radio operator can decode the info without any costly and complex equipment. The design strictly follows the KISS concept. It uses low cost, easily available components through out the design. A block diagram of the

Telemetering Beacon For VUSAT
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beacon controller is as shown: The controller can accept 16 single ended data channels of which the dc level represents the parameter to be telemetered. These channels are selected one by one (multiplexed) by using 2 number of CD 4051 (analog MUX). Voltage from selected channel is given to the ADC chip for converting this voltage to its digital equivalent. A channel counter (4-bit binary counter) controls the channel selection. This counter counts every clock pulse given to it and thus gives a 4 bit binary output. This binary is given to the analog mux as address of the channel to be selected. For every clock pulse to the counter, successive channels are selected. The channel select clock is derived from the end of message signal (EOM), which will be explained later. ADC chip used is AD7574. This chip is an eight bit Successive Approximation type ADC made by `Analog Devices`. This ADC starts converting the analogue voltage input when the RD! signal goes low and the digital value is available at the output pins approximately 15 microseconds later. RD! signal is derived from the "EOM" signal available from the EPROM. Eight-bit Binary output from ADC is given as the address of 8 most significant bits of the EPROM through two nos. of quad 2 input multiplexer chips. This two chips form an 8 bit 2 input multiplexer, one input is being the 8 bit binary from ADC and the other being the channel address (4 LSBs the upper nibble are...

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