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Small CUBEsat command decoders



CUBESAT Builders:

Today we tested an off-the-shelf DTMF decoder in a neutron radiation
environment and after subjecting it to the equivalent of 26 years in
space, it was still working flawlessly.  Since it is about the size of a
large postage stamp, it seems to be a good candidate for the TINY cubesat
and other simple student satellite designs.

It was a SPEC-COMM 809B DTMF 3 function decoder.  Typically advertised in
all radio magazines.  It was exposed to 3 rads per second for an hour for
a total dose of over 10,000 rads.

The professor in the Nuclear lab was amazed at its performance.  Another
very RAD-HARD RAM chip was exposed at the same time and it suffered 5
SEU's in the same time.  We powered up the DTMF module throughout the test
with no power cycles hoping to see if any SEU's would lock it up.  None.

So we doubt seriously that the DTMF PIC Processor is a hard device, but
that it probably has internal watch dog timers and good firmware that
receovers from any wandering code.  Our main concern was that the EEPROM
that stores the command sequences would not suffer any corrupted bytes.
None occured.

Our test consisted of simply sending the six command sequences over and
over for an hour and observing a proper decode every time.

de WB4APR@amsat.org, Bob

CUBESAT Designs     http://www.ew.usna.edu/~bruninga/cubesat.html

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