Intro: Tea Connector for Serial RS232 Cables
Serial cables and connections can be frustrating. There are 4 different connectors in common use ( 9 pin and 25 pin each both in male and female ) and 2 common ways of connecting them, straight through and null modem.
This project is my attempt to deal with the fact that no matter how many cables and adapters I collect I never seem to have the right cable/adapter.
A tee connector is a connector with 3 connections, a Tea connector is built in a Twinings Tea case and has 8 connectors, two of each common RS232. So it is a Octopus Tea Connector.
Step 1: Materials
9 pin and 25 pin connectors, 2 of each male and female. I got some from salvage of old computers and some from Radio Shack.( not the best place in my opinion ). They are generally easy to find.
A Twinings Tea Can: I like Prince of Wales Tea, seems to stimulate the RS232 signals.
Colored Wire, stranded fairly fine. Colored wire makes keeping track of the connections much easier.
DPDT Switch. You need this if you are using a 3 wire connection and want to have a null modem option.
Wire nuts or heat shrink tubing. For making or insulating the connections. Heat Shrink Tubing
Misc small nuts and bolts.
Step 2: Tools
Tools to cut holes in the tea tin, I used a drill, dremmel tool and finally a file.
Soldering Iron, wire cutters, and wire strippers.
Screwdriver, needle nose pliers......
Step 3: Mark It Up.
I put tape over the areas where the plugs were to be placed. Then I marked the shape of the connectors. If you are not happy with the layout take off the tape and try again.
Step 4: Cut It Out.
I drilled out the ends of the holes, then use a dremmel to remove most of the hole, and finally filed it to fit the connector. Then I drilled holes through a connector laid over the hole on the outside. This guarantees that the holes are in their right place.
Step 5: Wire It Up.
I normally use simple 3 wire connections so my connector is only wired for three connections. If you use more wires in your connections then you just need to wire them up, you may be surprised at how much wire you can use up.
Cut 8 wires of each color, I used about 8 inch long wires, you could probably use shorter one. Tin the wire ends and the connector ends. I just lay the wire on the connector and reheat the solder. Not the fanciest or strongest connection around, but seems ok. If you like insulation insulate it now. Heat shrink tubing can make a really neat job of it. I actually used some insulation stripped from a phone cable, seemed ok.
I connected the 4 connectors for the lower layer together, with an extra wire for the receive and transmit and ground, these will connect to the upper level. At this point you may appreciated the fact that the wires are color coded. I used a wire nut for some and when I ran out of them just twisted them together and soldered, then finished of with heat shrink tubing. Then I put the connectors in the lower level of the tin. Half way done!
Repeat for the upper layer of connectors, but tie the extra wires from the lower level in this connects the two layers together. ( if you use the null modem option below, do not connect the layers together, except for the ground, put an extra set of wires on the top layer and run the receive and transmit to the double pole double throw switch together. All the way done!!
Step 6: Use:
Plug one cable in a connector that fits, the other into another that fits. Since you have two of all 4 types of connectors this is always possible.
Step 7: Limitations
As noted above my version is just a 3 wire connection. Additionally ( while I have not encountered it yet ) the rats nest of wire in the connector may limit the maximum speed or cable length of the connection. Do not try to connect coffee pots.
Step 8: Options
Null Modem connections. A null modem connection switches some of the wires around, in a 3 wire connection the receive and transmit connections are reversed. It is easy to find a switch to do this so I added one, the switch sets this up between the top row of connectors and the bottom. If you use more wires finding a switch is a pain ( and may be expensive ) In that case I would build 2 different Tea connectors, one straight through, one with a null modem connection between the upper and lower layer.