This is a very simple project that lets you change a 9 pin female serial cable/plug into a male plug. This is useful when you need a sex change to connect. This actually happens to some of us. I wire mine for just 3 pins, but if you need more just wire it up. If this description and the pictures do not make this clear, then you do not need this device.
Step 1: Materials
2 9 pin male connectors ( mine are all salvage )
2 spacers, metal or plastic tubes see picture
2 bolts just long enough to hold the connectors together
Electrical tape or hot glue gun for insulation
Step 2: Tools
Wire cutter stripper....
Step 3: Step 1 Bolt together
See the picture. The trick is to have the spacers and bolts just the right length. A little cutting may be useful.
Step 4: Step 2 Wire it up
I just connect pin 2, 3, and 5. Beware of getting mixed up by looking at the connector from the wrong direction. These are the transmit, receive and ground. Use more pins if it is appropriate for your connections.
(Male 9 Pin DB-9)
1 2 3 4 5
\ . . . . . /
\ . . . . /
6 7 8 9
Viewed from front, the pin end.
Step 5: Step 3 Insulate it
Use a wrap of tape, or first pot up in some hot glue and then tape.
Step 6: Step 4 Use It
When you have an extra female and need a male, just insert the sex changer.
Step 7: Going Farther:
Make similar connector, but perhaps to a RJ45 connector, or use a null modem connection.
There is lots of stuff on RS232 and connectors to be found by Googling.
Finally a plug for my website, this page a long annotated list of links for electronics and robotics topics, they are intended to be easily enough to be accessible to high school students, but I think many have broader interest : http://home.comcast.net/~russ_hensel/RClub/ProjectLinks.html