vjp
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- Jan 23, 2009
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I've been thinking about building a MAD detector for a while now, but was
wondering if it wouldn't be cheaper and just as reliable to use a pair of CDS
photoresistors, once facing up, the other facing rearwards, in a voltage
divider configuration. Feed this into the op-amp (configured as a comparator)
with the reference voltage set to half V+.
When the rocket reaches apogee and begins to turn downward, the rear-
facing CDS sensor now "sees" more light than the forward facing CDS, and
the voltage at the op-amp input goes low (or high) compared to the reference
voltage, triggering the ejection circuit.
Obviously, there are probably some unusual weather/terrain lighting conditions
that could cause it to "see" a brighter ground than sky (i.e. a dark cloud
overhead and sunlit sand or snow on the ground), but I would think these
conditions would be the exception rather than the rule, in most parts of the
country and in most launch conditions.
Anyone ever tried this?
wondering if it wouldn't be cheaper and just as reliable to use a pair of CDS
photoresistors, once facing up, the other facing rearwards, in a voltage
divider configuration. Feed this into the op-amp (configured as a comparator)
with the reference voltage set to half V+.
When the rocket reaches apogee and begins to turn downward, the rear-
facing CDS sensor now "sees" more light than the forward facing CDS, and
the voltage at the op-amp input goes low (or high) compared to the reference
voltage, triggering the ejection circuit.
Obviously, there are probably some unusual weather/terrain lighting conditions
that could cause it to "see" a brighter ground than sky (i.e. a dark cloud
overhead and sunlit sand or snow on the ground), but I would think these
conditions would be the exception rather than the rule, in most parts of the
country and in most launch conditions.
Anyone ever tried this?