On finally getting on to wiring up my servos which I bought years ago to do the physical mounting work; I found one was misbehaving when I tested them in the system. After consulting with my supplier (Mendelssohn Pilot Supplies) I was very pleased with Danny's prompt service and soon had news that I could return my servo under warranty - that's great service from both Mendelssohn's and Dynon thanks guys if you are reading this! So at the moment I am waiting for word back and am in possession of only one servo.
Here is a drawing of my auto pilot wiring scheme
I am installing two Dynon autopilot servos one for pitch and one for roll. The skyview system talks to them over the two twisted pairs (I think 2nd pair is for redundancy) that it uses on all other network nodes. The servos need an independent power supply each which comes from two channels of my VP-X electronic fuse system they also need a ground return which I decided to run back to the firewall forest of earths rather than ground locally at each servo. Finally the servos require an autopilot disconnect which is a common signal sent to both and is active low. This signal will come from one of three sources either P1 Stick Switch, P2 Stick Switch or Panel disconnect Switch. I am planning to splice the P1/P2 stick signals together in the wing central spar area before feeding the common signals forward to the panel - more on that later.
To get all these signals to each servo you need some sort of splice as outlined in the dotted lines on the diagram. I went for locating this close to the branching point in the aircraft under the P2 seat. I originally made my splice using 9 pin D-Sub connectors but found them rather large and difficult to secure together and mount. After the problems with one of my servos I also decided there was also potential for plugging one in the wrong position and then opted for Molex Minifit-Jr connectors as shown.
I made a couple of angles fitted nutplates to them and made a mounting plate:
I have learnt that it is easier to have nutplates facing forwards in these tight spaces just the two central holes are used to secure the plate the smaller ones are drilled in error (unintentional lightening holes) I may remake this plate if the cosmetics get to me but it will do for now.
Pop riveting the angle brackets in place was very challenging as there is very little space for the tool:
I ended up using a 08 screw and nut in the top right position (just visible) after a lot of cursing. I would recommend mounting further forward in hindsight. wanted this removable for access to wiring and also if I ever need to go behind the plate for an unforeseen reason; eg if a part rolled under there.
I then crimper and wired it as per the drawing using twisted wire solder joints with heat shrink for all the 3-node joints:
Then I cut to length and crimped all the cables that plug into here double checked the wiring visually for consistent colours into and out of the connectors:
Here is the final assembly in place.
The pitch servo runs out to the right on the picture into the central tunnel and the up aft to the servo.
The roll servo cable runs out to the right wing (to left in picture) and was terminated with 20cm of loose lead on a free hanging receptacle as I have yet to site the Panel mount Plug side in the wing root.
I also made up the length of cable that runs up in the wing and terminated the ends to use as a test cable for my one servo which I tested in both roll and pitch positions and worked OK in both. Hopefully I will hear back about my faulty servo soon and will be able to test both together but don't anticipate a problem.
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