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dean.psiropoulos(at)veriz
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 Posted: Wed Feb 22, 2006 10:20 pm Post subject: Transponder/ RS-232 |
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Question on the Gray Code connection to the transponder. I have an Apollo
(UPS AT-now Garmin) SL70 transponder and it has a "D4" Gray code input. I
plan to use a Dynon EFIS D10 (not a D10-A) as my encoder but it does not
have a "D4" Gray code output. What should I do with this connection at the
Transponder end? Can I just leave it floating, do I need to ground it or
what? Don't see anything in the manual about this.
I also plan to connect my full UPS AT radio stack together at their
respective RS-232 Tx/Rx I/O interfaces. My GPS/COM manual says to use a
three conductor shielded cable for two way RS-232 communication (Tx and RX)
and two conductor shielded for one way communication (Tx only or Rx only).
What is confusing to me though is their wiring diagram, it shows two wires
PLUS a shield connection to the transponder (one way comm). One wire is
connected to RS-232 Rx, another wire to a specific ground pin at the
connector AND....a shield connection to the mounting frame of the GPS/COM.
First, I'm a little confused about what UPS AT is saying...since the
Transponder will only require one way communication then according to the
text, I only need a TWO conductor shielded cable! But from the wiring
diagram, it looks like I need two conductors PLUS A SHIELD!!!
Does that mean I need something like a shielded twisted pair for this
connection, or triax....or what?
Where would I obtain shielded twisted pair Tefzel wire for this purpose?
Thanks.
Dean Psiropoulos
RV-6A N197DM
Finishing Autocad and stripping wires.
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brian
Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA
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| Posted: Thu Feb 23, 2006 6:29 am Post subject: Transponder/ RS-232 |
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DEAN PSIROPOULOS wrote:
| Quote: |
Question on the Gray Code connection to the transponder. I have an Apollo
(UPS AT-now Garmin) SL70 transponder and it has a "D4" Gray code input. I
plan to use a Dynon EFIS D10 (not a D10-A) as my encoder but it does not
have a "D4" Gray code output. What should I do with this connection at the
Transponder end? Can I just leave it floating, do I need to ground it or
what? Don't see anything in the manual about this.
|
The Apollo stuff uses a serial code to communicate altitude information
to their radios (GPS, etc.). I don't remember if the SL-70 accepts
serial data in instead of gray code. I *think* it does but I am not
sure. If it does not you will need a serial-to-grey-code converter to
get the data from the Dynon to the SL-70. (I like the SL-70. I have had
one in three airplanes at this point.)
| Quote: | I also plan to connect my full UPS AT radio stack together at their
respective RS-232 Tx/Rx I/O interfaces. My GPS/COM manual says to use a
three conductor shielded cable for two way RS-232 communication (Tx and RX)
and two conductor shielded for one way communication (Tx only or Rx only).
What is confusing to me though is their wiring diagram, it shows two wires
PLUS a shield connection to the transponder (one way comm). One wire is
connected to RS-232 Rx, another wire to a specific ground pin at the
connector AND....a shield connection to the mounting frame of the GPS/COM.
First, I'm a little confused about what UPS AT is saying...since the
Transponder will only require one way communication then according to the
text, I only need a TWO conductor shielded cable! But from the wiring
diagram, it looks like I need two conductors PLUS A SHIELD!!!
|
They are using one of the wires in the bundle as the common and they are
using the shield separately as just a shield. This is the best way to
prevent ground loops and other noise pick-up. (The special ground for
mic input is isolated from the chassis.) I recommend you use the
approach shown in the wiring diagram with both the shield AND the wire
common/ground. It will greatly reduce the chance you might have a noise
problem on your mic.
| Quote: | Does that mean I need something like a shielded twisted pair for this
connection, or triax....or what?
|
Yes. In that case you will need two-conductor shielded (two center
conductors plus shield). If you have more signal lines you will need one
extra for common.
BTW, this is needed for mic and possibly for RS-232. It will not be
needed for headphone wiring. (In fact, you probably do not need even
shielded wire for headphone except in very rare cases.)
--
Brian Lloyd 361 Catterline Way
brian-yak at lloyd dot com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery
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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery |
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