Monday, February 8, 2016

The ACK E-04 ELT Instillation – The Saga Continues

My hope for this work session had been to finish off the instillation of the ACK E-04 ELT … but that was not to be because of the exorbitant amount of time spent on wiring four pins on the ELT’s miniature din connector, but more on that rant later.

Van’s places the ACK E-04 ELT on the right side of the RV-12 above the center channel and behind the right seat. The mounting tray that that comes with the ACK E-04 ELT needs to be riveted onto the inside of the fuselage after drilling a couple of mounting holes. The aft portion of the mounting tray is secured with Clecos using two existing rivet holes in the F-12122 bracket so the two forward holes in the mounting tray can be match drilled into the F-1204H bulkhead cap.
With the aft end of the ACK E-04 ELT mounting tray secured to the F-12122 bracket with Clecos, the forward two holes in the bracket are match drilled into the F-1204H bulkhead cap using a #30 drill bit.

After drilling the forward mounting holes into the F-1204H bulkhead cap, the mounting tray was removed and the two holes were deburred. At this point, two metal straps are placed under the mounting tray before it is riveted … the strap stamped BATTERY is placed under the aft end of the mounting tray and the strap stamped FRONT is placed under the forward end of the mounting tray. The rivets used to secure the tray/straps to the fuselage are the larger head SB-42-BSLF baffle rivet.
Riveting the ACK E-04 ELT’s mounting tray onto the fuselage using SB-42-BSLF baffle rivets.

With the ACK E-04 ELT’s mounting tray and straps riveted in position, the next step in Van’s plans instructs the builder to refer to the ACK E-04 manual for guidance on wiring the ACK supplied mini din plug (nightmare) connector that will furnish power and a GPS signal to the ACK E-04 ELT along with an optional test wire to verify the ELT is receiving the GPS signal. Here is where the wheels fell off the production wagon. For starters the ACK instillation manual says the mini din connector has solder cups and that the wires are to be soldered… the connector they supplied in the box DOES NOT have solder cups, it has gold pins. Included in the Van’s hardware for installing the ACK E-04 ELT are 4 gold plated female pins of the crimp variety and of the type designed to be enclosed  in a connector housing. The spacing of the pins makes the connectors practically touch one another and if the wires flex they will touch. Once the connectors are slipped over the tiny (and very short) pins on the mini din connector, they almost touching one another … especially at the base of the pins and they are very wobbly and easily moved by the wires. Frankly, this is the worst interfacing I have ever seen … the setup is totally daft. I was half tempted to chop off the mini din plug and use a "real" four wire plug and socket designed to fit together … but figured I could improve on the hot mess and move on so as not to have to wait for parts from Mouser. If this connector gives an inkling of trouble, it will be chopped off and replaced with a quality connector.

For starters, instead of soldering the wires to the female connector pins, the tiny pins were crimped using my crimping tool with special dies for tiny connector pins. All the crimps turned out better than expected considering how tiny the pins are.
Placing a wire in the jaws of the crimping tool.
Zooming in on this photo of the GPS signal wire and the ground shield, one can see the pins supplied are a split female type without any insulation or a connector body to fit into like they are designed for … frankly, in my opinion, all wrong for this application and beyond daft!!

In an effort to mitigate possible shorting of the connectors and to make the connections tighter, after the wires were crimped onto the pins, a piece of TINY heat shrink tubing was placed over the female pin and was left a few thousands longer than the female pin … then a heat gun was used to shrink the tubing before sliding the female pin onto the tiny male pin on the mini din. This made the female connector fit much tighter onto the tiny male pins coming out of the mini din connector because the heat shrink compressed the female fitting tighter to the pin.
Zooming in on this photo, one can see one female pin has the heat shrink covering it and the other does not. The viewer can see just how close these pins come to touching one another along with also seeing how tiny and short the pins exiting the mini din are.

The ACK wiring instructions say to connect the white/red power wire to pin 1, test data out to pin 2 (this is a short piece of wire that is not necessary but can be used as a troubleshooting aid to verify a GPS signal is being received), the shield ground from the GPS cable to pin 3, and the GPS signal wire to pin 4. The pin callouts in the ACK instructions are viewed from behind the connector on the side where the wires attach.
All the wires are now connected onto the mini din connector.

The ACK instructions say to fill the connector body with RTV … so the high temperature RTV that was available in the hangar was squeezed into the connector body and the two halves placed together. Before sliding the housing up over the two halves, more RTV is placed on the wires where they exit the two halves of the connector then the body is slid up and over the two halves locking them in place.
The mini din connector sitting in half of the housing. RTV will be used to cover the wires and fill the housing before the other half of the housing is mated.
Finished connector with a little red RTV oozing out the slots on the back of the cover.

Not wanting to disturb the wires until the RTV has had a chance to cure a little, will wait until the next work session to mount the ELT unit and audio panel onto the mounting bracket then dress the wires and keep my fingers crossed the mini din connector is functional.