I fly FPV drones, and one of the best purchases I made was the DJI Digital FPV Goggles. They support 720p video at 120hz (that's amazing) all while having great range over analog video. But there was a solid chunk of time where I didn't have the yet-to-be-released small version of the video transmitter that actually goes on the drone. I decided to retrofit an analog receiver I had onto the goggles using their AV input so I could use them with traditional analog systems. Products already existed to do this, but nothing sleek and sturdy. Most were floppy adapters that sat on the side of the goggle and bulged outwards. This was designed to integrate into the existing shape as best as possible.
The Build:
This is probably one of the most compact areas I've ever had to work with. I had to design the product around the container it went in. I could change the faceplate design as much as I wanted, but I couldn't make it too large or the antennas would protrude too far, or too small and the delicate mechanisms inside could be damaged. My main goal for this project was to 1) make it compact and 2) not void the warranty. This meant no internal soldering, no disassembly past removing the front plate, and no physical modification of the goggles.
This is the space I had to work with. Not only incredibly confining, but oddly shaped and with weird protrusions to boot. I had to fit a video receiver, its accompanying diversity (second antenna) module, and a 5v BEC to power everything. I also added a switch later, managing to cram it underneath the diversity module with a few well-placed cuts on the
switch.
These are the final parts. The receiver and BEC are on the left, stacked on top of each other, and the diversity module and switch are on the right. This meant I had to run power from the switch to the BEC then into the receiver via that white connector on the leftmost part of the assembly. The 4 pole headphone jack plugs into the analog input of the goggles, providing video (no audio). It's connected via the yellow wire running to the top of the diversity module. The signal and power cable (white braided one in the middle) that runs between the receiver and diversity module can be disconnected, so I used bullet connectors to connect power from the 16.4v source to the BEC. This enables the wires to slip behind the middle plastic that separates the two holes and lets me take the device off of the goggles, allowing me to do maintenance (or take these pictures) without desoldering.
Designing it:
This design started out when I saw a similar product online. It was built for a different receiver type that was one-sided, and also protruded far too long for my liking. I figured I could make one myself! I started by finding a model of the faceplate (originally metal) to design my version around. I found a model by Crazyguy_FPV on Thingiverse that had a module bay on one side. I cut it in half and mirrored the halves to create a blank faceplate to start with. My initial idea was to do something similar to Crazyguy_FPV and make a module bay for the receiver to sit in, but recess it back into the hole in the goggle. This... didn't work. I printed a bunch of tests and couldn't get anything to fit properly, much less be compact. It was taped together for a few weeks until I found time to re-do the model properly. This time, I started with this model of the module bay doors instead. I discovered that the receiver module snapped into place in the door, and could be held on even more securely by the antenna. Gone was the idea of putting the module into a bay, now I just put a plate on top that was perfectly fitted. I essentially designed an inverse bay, with the receiver attaching to the front plate and being open in the back. I extended this inverse bay outwards until I could fit the components behind it. The diversity receiver is far slimmer and only needed a slight protrusion. I also smoothed the module bay door cover to not have any extra holes or clips that were present in the original model.
Once I got everything to fit using test prints, I decided to order a professionally-printed part with higher accuracy and durability. I used jawstec.com to print the part in MJF nylon. The resulting part will be of a much higher quality than anything I could do with my FDM printer. The part cost about $23, which is actually on the cheap side. It turned out great. It was so strong I had to use a drill to cut a hole for the switch to fit in. The resulting part is has a rough (but in a quality way) texture and fits everything perfectly.
Here's a picture of the wiring and some other closeups:
Final Result:
Take a look on Thingiverse!