I wanted to share a little project I have been working on for the last few weeks regarding the wiring of the Pixhawk and DF13 connectors.
During flying my Skywalker X8 last year I had a failure of GPS, thankfully while on the ground before the first flight. My current setup has a custom wiring rig as the stock cables are simply not long enough for a big model without compromising the placement of devices. While building the X8 I decided to solder on the pins for the DF13 connectors, which worked great. However after some time the wires tend to break off as there is no strain relief, which of course I first discovered when the GPS failed.
This year I decided I didn't want to take any chances, I am very particular with redundancy and flight safety and I have yet to have a crash due to component failure. Having a cable break and cause a crash would be a particularly frustrating way to destroy a plane!
The solution I came up with solves two problems, firstly it eliminates the need for having to make up DF13 cables. Secondly it provides a way to run all connections for the Pixhawk to anywhere in the plane using simple IDC cabling and connectors which can be made up easily to suit the application. Also it provides the receptacles for damping balls to help minimise any vibration problems.
The main carrier PCB features a space in the middle to attach the Pixhawk by normal means of a sticky pad. Around the outside there are sockets for all of the DF13 connections, RC connections and power. Every connection on the PIxhawk connects to the carrier PCB using the (short) standard cables available and standard 0.1" plugs. On the bottom of the board there are two 34 pin IDC connections (standard floppy disk cable) that carry all of the signals to a pair of daughter boards that break out the signals and power using 0.1" headers, which of course are easy to make with a cheap crimper. The plan for the peripherals with DF13 sockets is to make DF13 to 0.1" adapters using standard DF13 cables and cutting them in half, then putting 0.1" connectors on the bare wire end.
There is a larger daughter board that connects to both ribbon cables and makes all of the signals available. There is also a smaller daughter board that connects to one of the ribbon cables that makes some of the signals available. The idea is the Pixhawk sits in the middle of the plane, the optimum position for the IMU to move around all three axes. The smaller daughter board goes at the back of the plane and gives access to power, I2C, CAN, USB, PWM and the switch, allowing the power electronics and motor to be connected at the back of the plane. I also included a spot for a zener diode to protect the servo rail from over voltage.
The larger daughter board then goes at the front of the plane, keeping the sensitive electronics as far away from the motor as possible. The larger daughter board breaks out all connections allowing for any configuration of instruments and equipment at the front.
This board is of course designed for the X8 and may be of interest to anyone with this airframe, although I'm sure it would work for anyone using a large/long fuselage. I am still assembling the first one and have yet to install it in the plane however I wanted to open a discussion to see if this kind of device would be of interest to the community. The first spin of the PCB was not intended for sale but after recently reading a (very long) thread about DF13 connectors I began to wonder if there was scope to design something that solved these problems that was commercially available. Thanks for reading!