Introduction: Make Custom Cables With Hot Glue and Shrinking Tube
I own a WRTnode board - a very interesting 600MHz development board for OpenWRT distribution. So instead buying a WiFi router able to run OpenWRT and start disassemble it and soldering various cables, you can use WRTnode - all the signals are accessible out of the box. WRTnode can boot your personal OpenWRT compilations straight from USB stick, so you will not harm the board. (details about the board on http://wrtnode.com/ - PS: I am not WRTnode team affiliate).
Somehow I managed to brick the board, I did my best to fix it, eventually I had to make 2 cables: one cable for serial connection (made from a Nokia mobile phone USB data cable) and a second cable for Ethernet connection (one end has a RJ45 connector). WRTnode has 2 rows pin header (male) with useful signals: 3V3, 5V, GND, Ethernet, I2C, SPI, serial Rx / Tx, USB and so on. In order to connect to these signals, I had to use 2 rows headers female on my cables.
Just an observation: comparing to USB-to-serial modules, it is cheaper and less time consuming to use such mobile phone USB data cable, just cut the end phone connector, solder the wires to your connector and that is it.
I soldered the wires from my cables to the female headers according to the WRTnode pin map, but the cables are not looking very good and also I am not sure these will last long time.
Searching for Instructables, I found ideas to use shrinking tube, hot glue, Sugru, insulation electrical tape... Some ideas were looking good, some not, some were simpler and so on.
So why not combining shrinking tube, hot glue and a hot air gun in order to make some long lasting cables with header connectors (and maybe for other connector types)?
Step 1: First Attempt Using Hot Glue and Shrinking Tube
My idea was simple:
-the hot air gun will melt / soften (again) the hot glue inside the shrinking tube
-the shrinking tube will shrink and it will distribute the hot glue evenly inside the tube (even filling air gaps)
-afterwards I can give a shape to that end of the cable.
Things went fine until I noticed that hot glue is coming out of the connector's holes because: hot glue melted inside the shrinking tube, shrinking tube shrink and pushed the hot glue to the path of minimal resistance :)
So back to the drawing board!
Step 2: Second Attempt Using Hot Glue and Shrinking Tube
Solution to the problem:
-use machined headers, these have no holes
-block the holes somehow.
I had to take choice number 2.
I took a sheet of paper, I punched the connector's pins to the paper and trimmed the paper to match connector size.
I soldered the wires, I checked the cables (connect them to the PC and to the WRTnode and see that are working from an electrical perspective).
After I was sure that these are working cables, I put hot glue, left it a while to harden, then put the shrinking tube and use the hot air gun.
Step 3: Lesson Learnt
As you can see, cables are looking good, definitely they will last longer.
Lesson was: never squeeze hot glue, it will go outside if there is a hole! (pretty obvious, isn't it?)