Tutorial: How to build a serial port plug

Archived 2013-12-08
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Contents of this page:

here is the description how I built my own serial port plug for the HP 200 LX.
In this case, I wanted to connect a mouse directly to the port, without all these HP-cables and adapters. So I soldered a plug fitting into the serial port of my HP 200 LX directly at the cable of the mouse.

Please notice that I found two methods for making a connector. Here you can find the first one of them. The second (newer and I think better) method you can find below.

What you need:

2 pcs. "Platinensteckverbinder 5-polig, Rastermass 2,0mm" - In English this should be a "Socket strip" 2.0mm pin spacing, 5 pins in a row. See pictures: pic1, pic2, pic3!
You can get it from Segor Electronics.

Segor Electronics
Kaiserin-Augusta-Allee 94
10553 Berlin
Telephone: +49 (0)30 3449794
Telefax: +49 (0)30 3453968
email: This email address is being protected from spambots. You need JavaScript enabled to view it.

It has the part # 15606, part description "PC- 405" and costs DM 2,80
(+ shipping).

several diameters of heat shrink tubing (German: Schrumpfschlauch).
I used diameters of 12.7mm and 4.8mm, each about 4 cm of length.

a soldering iron



Take the two 5-pin-connectors and the superglue.
The connectors have one side with little plastic lips for each pin and one totally plane side.
Glue both totally plane sides together with about two drops of superglue. press strongly, but don't glue your fingers to the connector. This combo won't fit into the palmtop's serial port! :-)

Try to plug the 'double-connector' into the serial port. if it fits in there and if you can pull it out of the port without applience of
violence it's good.
Otherwise you have maybe glued not exactly.

Find out which pins you'll need for your application, cut off the not needed of the ten cables of the connector. make sure that
no cutted cable contacts another! you can isolate them with a little drop of (normal) glue.
To find out which signals you need, check out my serial port info!
I have no solution for a mechanical protection from plugging upside down, so please make a little mark on the upper side of the connector!

Shorten the needed wires of the connector to various lenghts from
about 1 cm in steps of 0.5 cm. after that the connector should look
like this (only one half is shown):

|       |_
|       |_______
|       |_
|       |______________
|       |_________________________

In this example are two cables cut off and three needed cables shortened to various lenghts.
No cable should have the same lenght like another, because after you soldered the cables of your device (mouse, LED light, modem... whatever) to the connector, there would be short-circuits between the wires!

Do the same as under (d) with the cables of your DEVICE, but in reverse order (so that the cables fit exactly to the corresponding cables of the connector!)

Evaluate how much of the heat shrink tubing (diameter ~4.8mm) you need, cut it and push it over the cable. the illustration shows from where to where the heat shrink tubing should reach after mounting it in its final position:

|      |_                                   _____________________
|      |_____ -----------------------------|
|      |_                                  | cable of device
|      |__________ ------------------------|
|      |_____________________ -------------|_____________________

from here ^                       to about here ^
(first layer of heat shrink tubing)

Remove about 2mm of the insulation of the wires, solder the wires of the connector and the wires of your device together. in the ASCII-'picture' the soldering points will be shown as 'O'.
If there are short-circuits between your soldered points, you must insulate them with PAPER (DON'T USE PLASTIC TAPE - IT WILL MELT WHEN HEATING THE HEAT SHRINK TUBING!!!)

Push the heat shrink tubing back over the soldering points into its final position (as shown in (f)). It must be as close as possible to the connector!

After that it should look like this:

                                                heat shrink tubing
 _______  ========================================================
|       |_                                       ____________________
|       |_______O-------------------------------|
|       |_                                      | cable of device
|       |______________O------------------------|
|       |_________________________O-------------|____________________
|_______| ========================================================

Heat the heat shrink tubing CAREFULLY (don't melt down any insulations or the connector!)

Push another heat shrink tubing (diameter about 12.7 mm, lenght about 4 cm) over the connector and the cable like this:

hst 12.7mm
===============================================        hst 4.8mm
 _______ =======================================================
|       |_                                  ________________________
|       |_______O--------------------------|
|       |_                                 |  cable of device
|       |______________O-------------------|
|       |_________________________O--------|________________________
|_______| ======================================================

and heat it, CAREFULLY, too.

DON't FORGET TO MARK THE UPPER SIDE OF THE CONNECTOR! If you plug a mouse connector upside down, it won't destroy your machine or the mouse (I have tried it :-) ), but I don't know if it is the same with - say - modem connectors or something else!



the plug

mouse connected to the palmtop running windows 3.0

close view of the plug connected to the port


I'm not responsible for physical or other damages to your devices. The descriptions I made may contain errors which could cause serious damages of your palmtop or your peripherial devices.

Second way of making a serial port plug

Contents of this section:

Here's the second idea that I had to make a plug for the serial port.

I think it's a little bit easier to make (and easier to understand, too!) and the result is much more solid than this one of the first way.

I took pictures while I made it, so I think you will see how I made it.
So I don't have to write much describing text and you don't have to read much of my English.

Here's what you need INSTEAD of the two 5-pin-'Platinensteckverbinder' from Segor Electronic that you need for the first way:

What you need

Main parts for the plug:

  • 1 piece 2 x 5 pin "machine-screw header receptacle" connector with 2.0mm pin spacing (See the pictures: pic1, pic2).
    Such an item can be obtained at Conrad Elektronik (Germany), it is part number 739251.
    Alternatively you can use a laptop IDE hard drive connector. It has the same distances between the pins. For instance, you can buy a 2.5" to standard IDE connector adapter to get that connector.
  • 1 circuit board (both sides must be coated with copper!) that has such a thickness that it fits exactly between the two rows of the connector pins, i.e. it should have a thickness of 2.0mm.
    The circuit board must be at least 1cm * 2cm. If it's bigger, you have to saw it into the size of 1cm * 2 cm.

In addition, you need only:

  • a soldering iron
  • something to groove the copper coat of the circuit board, like a good knife or a small rotary grinder
  • epoxy glue
  • heat shrink tubing


When you watch the pictures now: please notice that I used this plug for making an LED light, so I only needed the pins 3 and 5 of the plug.
If you want to use it for serial communication, you have to make another layout of the little circuit board!
For informations regarding which pins you have to use please have a look at my serial port info.

Step 1

Put the connector on one side of the circuit board and mark where to saw the board and where the pins will take place later.


Step 2:

Saw the board into its size of 1cm * 2cm (the 1cm must be exact!).
Saw the connector in its size of 2*5 pins if it isn't already.


Step 3:

Design the board: make sure which pins you have to use, insulate all pins from each other and carry through these ones which you need.
I used a rotary grinder for that (rotary grinder = german 'Fräser'). Maybe a simple knife works, too.

The two holes I made were for the stiff wire that holds the LEDs of the LED light.
They might also be usable for holding a thin cable.

the bottom of my board (pins 6-10; not used in my case)

the top of my board (pins 1-5; pin 3 and 5 are used here)

Step 4:

Solder the 2*5 connector to the board (avoid short-circuits between the pins!)

the bottom (pins 6-10)

the top (pins 1-5)

Step 5:

Solder all the cables you need to the board.

If everything is soldered and you verified that the plug works, cover it with epoxy or hot glue and a fitting piece of heat shrink tubing.
You can also try to place a little blob of epoxy glue onto the top of the connector, so that it becomes impossible to plug the connector upside down into the palmtop´s serial port.


I'm not responsible for physical or other damages to your devices. The descriptions I made may contain errors which could cause serious damages of your palmtop or your peripherial devices.

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Daniel Hertrich