Fat Shark FPV Goggle Battery with ON/OFF Switch and Power Indicator by jellofrog

Last crawled date: 3 years ago

Back Story
In between flights as I am switching out packs on my model I unplug the barrel jack from the goggles so as not to waste the power while they are just resting on my forehead. I am sure many of you do the same. My problem comes when it is time to blindly plug it back in while it is on my face. I will grope around with my fingers, misidentify the headphone jack as my target and struggle in vain for an embarrassingly long time to force the battery connector into it. A case could be made that if I am this clumsy with my hands, perhaps I should not be piloting drones. You may have a point. I will ponder this later.
Functionality
I decided to make a battery pack that I could leave plugged in and simply switch off when I don't need to draw power from it. While I was at it, I added a power indicator LED. The LED works differently than you might expect but you are free to build it any way you like or just omit it altogether.
Build Details
In my build, when the pack is switched "ON" it glows brightly when the pack is at 8.2V and gets dimmer all the way down to going out at around 7V. At its brightest the LED only draws a negligible 1mA of current when turned on. The wiring diagram is attached but I basically added a Zener diode in series with the LED to create the dimming behavior described above. These are just soldered point-to-point. I arrived at the Vz value experimentally and found 5.6V to be a good fit. If you don't want to go to the trouble just put an appropriately sized current limiting resistor in place of the zener diode. There is enough room for all the wiring but it is a tight fit in order to keep the overall size of the unit down.
Four M3x14mm screws are used to fasten the front and back pieces from the back side. I made the front and back cover from PETG and the strain relief block out of TPU. TPU or TPE is recommended for this particular part. As you will see in the images, the inside of the strain relief block is meant to be cinched down upon the cables with a small zip tie that will stay concealed inside the case when the project is complete. For this reason, the part was designed with the expectation of a reasonably flexible material. The stuff I used has a Shore hardness of 95A and it worked very well but I would not go any higher.
Happy building and please post your makes!
Parts List:
2S JST-XH cable
18650 Li-ion Cells
Two Position Switch
Zener Diodes (optional)
5mm Blue LED
M3x14mm Thread Button Head Hex Screws
Hatchbox Blue PETG Filament (used for cover)
SainSmart White Flexible TPU (used for the strain relief block)