This is a simple USB plug is a two-pin connector for laptop fans as used in my blower stoves. It is, cheap, robust, ‘repairable in the bush’ and compatible with the existing cables and sockets on the laptop fans.
The laptop fan cables are designed for the gentle static environment inside a computer and not that of a campsite. I had one bad experience of the fan cable pulling the printed circuit connection off the plastic fan housing. This luckily was toward the end of a 4 day overnight Easter walk. I now anchor all fan cables to the fan housing to prevent this from happening. However, I still needed a better way of connecting the USB power to the fan power socket.
I also wanted the electrical system to support a small elevated LED light for illumination of the cooking at night time. For more details on the lighting module please see LED Lighting.
I have tried a variety of commercial connectors but none have met my requirements, so I have settled on a DIY ‘fang fitting’. This fitting is crude but light and robust (“bushwalking boot proof!”). It has two copper pins that mate with the fan socket. The positive pin is slightly longer than the negative one so that it can be identified correctly for connection to the red wire (positive) on the fan socket.
The copper pins are strong and are soldered to the USB power cables and are separated by a tapering cane insulator and are bound together with whipping cord at the same pitch as the fan socket. The whipping and tapering cane is extended onto the power cable to form a soft transition from the stiff plug ‘handle’ to the flexible cable. This fang fitting is a little crude looking. It is designed to be left in place, connected to the fan cable socket, for the duration of an extended walk. This is to avoid its loss and to maintain polarity.
“In my earliest designs I left the fan connected to the battery and used a switch on the battery box to stop the fan. Although this was a convenient feature while cooking, one time I had made a big shared pot of soup for lunch on a cold day and found out to my dismay at dinner time that my fan had been quietly running in my backpack for some hours (left on or bumped on). Luckily there was still enough power in my spare batteries to finish the trip. “A disconnected battery is the most secure one when not in use.”
The fan’s cable is supplied with a little ‘two-pin socket’ that is designed to mate with protruding soldered PCB pins on a motherboard of a computer. These little fitting have stood the test of time during my many adventures. With reasonable care they are; suitably robust, simple to connect and make good electrical connections. They are also quite good for quick fault testing, and jury-rigging with alternative connections and power supplies (wires, pins and sticky tape etc).
Lastly, removing the USB A plug from the power supply can be used as a switch to turn off the fan (another excellent switching option is discussed below).
“On the first day of an 8-day walk, I unknowingly lost the plug and cable behind a log that we sat on it after boiling water for a lunchtime cup of tea.”
After this mistake, I designed the cable to be semi-permanently connected to the blower fan by the ‘fang fitting’, so that leaving it behind or lost is very unlikely.
The LED light can be turned on or off by it’s insertion or removal from the jack socket. The lighting module can also be used independently as a small light when the fan is disconnected (e.g. as a tent light).
Addendum. Now I also protect the blower fittings from damage by making a single assembly of all electrical parts. This means that there is no need for any significant movement between them when they are moved. The components can still be disassembled for convenient compact backpacking inside the stove body and pots.
I have made a further refinement of the electrical system that avoids the need to remove the USB plug as a ‘switch’. The switch is described in another post (pulse power supply to extend battery life).
Tim
gge
