Virtual Integrated Design

RS232 Monitoring Cable Schematics

 


Half Duplex Cable -



The schematic below is used to make a half duplex RS232 monitoring cable.

RS232 Half Duplex Cable

This cable is used for monitoring 2 devices communicating in half duplex fashion, that is, one device would send data and the other device would receive data. Both devices cannot transmit at the same time with half duplex, if that happened the data would be unusable.

RS232 Hex Com Tool can be used to receive either ASCII or Hex half duplex data. Also RS232M Com Monitor can monitor 2 sets of half duplex communicating devices (1 set in each window).

Here is a parts list for the half duplex cable with Digikey parts:

1 - M/F RS232 Cable, AE1020-ND.
1 - Female RS232 DB9 Connector, 209F-ND. or
1 - F/F RS232 Cable, AE1016-ND.
1 - 1.38" x 1.97" Enclosure, HM375-ND.
2 - 1N4148 Diode, 1N4148DICT-ND.

NOTE: If the female DB9 connector is used a standard M/F RS232 cable is needed to connect to the monitoring PC. Otherwise a second M/F cable can be used instead of the female DB9 connector.
(Digikey parts at www.digikey.com )

Assembly:

1) Drill 3 holes in the enclosure (at the center line) the size of the RS232 cable for a snug fit.
2) Cut a rectangular hole in the side of the enclosure that will fit the female DB9 connector using a nibbling tool, replacing 1 of the round holes.
3) Align the DB9 connector with the enclosure and mark the 2 mounting holes.
4) Drill the mounting holes and mount the connector with 4-40 screws. 
5) Cut the RS232 cable in half, insert the cut ends through the holes in the enclosure, strip the ends back about 3" and strip the insulation off the individual wires.
6) Twist the diodes together at the cathode and solder into pin 2 of the DB9 connector (or the red wire of the F/F RS232 Cable).
7) Twist the red wires together and twist the orange wires together.
8) Solder the red wires to one of the diode's anodes and the orange wires to the other and cover with heat shrink tubing.
9) Twist the rest of the wires together, solder and cover the exposed ends with heat shrink tubing.
10) Assemble the enclosure.

NOTE: Skip steps 2,3 and 4 if using the F/F RS232 Cable instead of the connector.



Full Duplex Cable -



The next cable is used for monitoring full duplex RS232 communication.

RS232 Full Duplex Cable

For devices that may transmit data at the same time, this cable is the one to use. RS232M Com Monitor can display both sides of full duplex RS232 communication.

This is the parts list for the full duplex cable, again using Digikey parts:

1 - M/F RS232 Cable, AE1020-ND.
1 - F/F RS232 Cable, AE1016-ND.
1 - 1.38" x 1.97" Enclosure, HM375-ND.

(Digikey parts at www.digikey.com )


Assembly:

1) Drill 4 holes in the enclosure (at the center line) the size of the RS232 cable for a snug fit.
2) Cut the 2 RS232 cables in half, insert the wires through the holes in the enclosure and strip the ends back about 3".
3) Strip the insulation off the individual wires, twist the wires together, solder and cover the exposed ends with heat shrink tubing.
4) Assemble the enclosure.

 



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