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DIY USB 2.54mm Fang Fitting

PostPosted: Thu 03 Jun, 2021 8:34 pm
by telemarktim
Hi there, Fellow MYOGers, I guess that you also tinker with low voltage powered gizmos for your bushwalking.

We are now blessed with so many wonderful inexpensive electronic devices. Equally inexpensive rechargeable 18650 lithium-ion batters and….. tiny power packs that house the battery/s and….. manage charge/discharge and……. short-protection. This all makes the USB 5V DC power supply standard that looks as though it is here to stay. It is irresistible for our backpacking adventures.

However, the range of USB plugs and socket seems endless. I also like to bandicoot parts and fitting that are designed for the gentle static interior of PCs or Laptops PCBs. These have plugs and sockets for conductor pins set at a standard 2.54mm pitch with a pin diameter of ~0.8mm. These fittings, at first sight, are not exactly meant for rugged use with bushwalking, skiing, camping, campfires and tired people wearing clunky walking or skiing boots.

Despite this, in my experience, a universal USB power plug and socket can be simply made by MYOGers such as us. They can survive the above challenges. They also have the advantage of being repairable, or jury-rigged on the trail, with things from a modest repair kit or even a first-aid kit. “Try doing that with any ordinary USB plug or socket at camp!”

The DIY USB Fang Fitting. The USB fire blower unit shown below is connected to the power supply by my DIY Fang Fitting that plugs into an industry-standard 2.54mm PCB socket. “A robust fitting that if ever needed can be repaired in the bush.

In the photo below the fang fitting (in the middle of the cable) is connected to the blower stove fan via the little white factory fitted 2.54mm PCB socket.


The photo below shows the detail of the exposed fang fitting formed on the end of a power cable that is plugged into a power bank with a USB A plug. Normally, I would not leave the pins exposed to the risk of shorting. The positive pin is left a little longer to easily identify it. It also makes docking with the socket easier as the positive pin can be in place while the negative is being aligned.


I normally leave the fang fitting in a socket of a device. This eliminates shorting issues and helps to not lose the cable in the hurly-burly of bushwalking. The USB A plug in the power pack would be disconnected to cut the power to the fan and the little cable would be left attached to the fan.

The connector pins. I use two 0.8-0.9mm diameter soft copper pins (salvaged from discarded house wiring. Now that’s my Green Credentials ticked). I make a slightly shorter pin for the negative pin.

I 'tin' the copper pins with solder and I do the same for cable wires. This makes the subsequent soldering between the pin and the wire very easy. The long pin is soldered to the red (positive) and the shorter pin to the black (negative) power wires of cheap off-the-shelf USB A plug and cables.

Fitting the cane spine. After the soldering, I make a flat slice of a cane grilling skewer. This goes between the two pins. A sharpened long point on one end of the cane slice so that it can be pushed up inside the plastic sheath of the cable will stretch and swell a little. This provides the fang fitting with stiffness and later prevents fatigue at the soldered junctions. It also will help to form a useful plug handle.

Alignment and testing. After the soldering, I trim off any excess cane, then the pins are temporarily inserted into a 2.54mm socket to set their pitch. For this, I use the factory fitted socket on a flying lead on a Laptop fan. At this stage, I do a test of the solder connection and correct polarity by seeing that the fan runs at full speed.

Note: The fan motors are polarity protected, by diodes, so they just don’t work if connected the wrong way. Similar to most LED lights because they are diodes. I only use USB power banks and lithium-ion batteries that each have their own short protection built-in. These dual measures make a battery melt-down and explosion by shorting double unlikely.

A strong protective and waterproof cover. After the testing, with the pins in the socket, I smear the fitting with an excess of acetic cure RTV silicone rubber and bind or whip the fitting with thick cotton, nylon or wool thread that is also impregnated with the rubber. The whipping generously covers the electrical junctions and I extend the whipping so that it covers the portion of the cable sheath that has the spike of cane within it. Where possible I mount the power supply on the device that it powers so that the cable is protected from pulling forces. It also makes it easy to use with one hand while camping. Similarly, I anchor a bend in the fan cable in a hole in the fan housing to prevent the wire from being pulled off the tiny motor.


The final finish. I check that the negative pin is significantly shorter than the other pin and trim a bit off if needed. This is so that it can be identified by touch. Then I clean the copper pins with sandpaper to remove soldering flux, glue and oxide. I also use sandpaper to round the ends of the pins so that they make an easy and soft entry into the conductive spring clasps of the socket. (If the pins are left very long they can be used as a connector for double or triple adaptor sockets but that's for another post along with a jack plug fang fitting.)

“I can hear the nit-pickers crying.. Ohoh…… acetic acid is bad for conductive metal. I simply say that it works and it avoids the nasty toxic solvents such as toluene that are in most other rubber glues. Feel free to poison yourself.”

Note: Please see BarryKs warning (link below) about voltage loss in very thin and cheap copper conductors in some cables. I have only use the thick conductors for my fittings and keep the cable length very short.

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