nuckollsr(at)cox.net Guest
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Posted: Sun Jan 08, 2006 11:04 am Post subject: Diodes in the Altitude Encoder data lines |
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Quote: | Comments/Questions: Hi Bob,
I will be installing a digital chronometer with a built in altitude alert.
The manual calls for a 'T' connection to be fabricated to connect to the
existing altitude data lines between Encoder and Transponder. Is this a
simple process of connecting two wires per pin on the encoder DB-15
connector? Excuse the simple question but I have found no reference
regarding the correct methods in fabricating a 'T' connection. Also, I
have seen your wiring for two systems to share one encoder, which shows
diodes in each line, the manual does not call for diodes to be installed,
is there any harm in omitting the diodes?
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Don't know. In the earliest days of multiple clients
sharing the output from a single encoder, diodes had to
be added in series with each of the client's data signal
lines to prevent a powered-down client from loading the
data bus an killing data to all clients.
Over the years, many folks have either added the diodes
internal to their product or designed the outside world
interface so that the powered down client cannot load
the altitude data bus.
You would have to ask the folks who supplied your
accessories as to whether the product includes bus
isolation features friendly to other devices sharing
the bus.
If the answer is "yes" then your supposition is adequate
and correct but I don't think I'd try to put double wires
into the connector. Taps into the wire covered with heat
shrink for finish would be my choice for installation.
If you need diodes for either client, then an etched circuit
board assembly with diodes and d-sub connectors would be
a cleaner approach. You might ask a local avionics shop what
they use for isolation diode installation techniques. There
may be some whippy adapters that I'm not aware of.
Bob . . .
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