I have a motley collection of small action cameras. Most of the time, I use them to capture in-flight video with my RC aircraft. I stopped using some of these cameras as they developed problems and annoyances over time. I finally decided to address each of the issues and get all of my dusty gear up and running again. This required me to perform some repairs and a few upgrades. I'll show you how I cracked open these little cameras and got them back into service.
Mobius Battery Replacement
One of my Mobius cameras had developed very short battery life. A fully-charged battery would last only a few minutes. I opened up the case to have a look. The 2-piece case is attached with tiny Phillips screws in the front and plastic latches in the rear.
The Mobius is powered by a single LiPo battery. Dead (or dying) LiPo cells will often swell up like a balloon, but this one had no obvious physical defects. I detached the power connector from the camera PCB and charged the battery on one of my hobby-grade LiPo chargers. This allowed me to rule out any problems with the camera's built-in USB charging circuitry. My run time results were still way below normal, so I was confident that I had a dud battery.
I ordered a replacement battery from Buy Mobius for $7. Both of my Mobius cameras are from an early production batch and were equipped with 520mAh batteries. The factory later switched to 820mAh cells for longer run time. My replacement battery is the 820mAh variety. The newer battery has almost the exact same footprint as my original. It's just a little thicker.
The stock battery was held in place with a small square of double-sided tape. I was able to pry up the battery with my finger using gentle pressure. Even the tape was salvageable. The new battery fit into the same spot without any modifications. Since the replacement battery has the appropriate power connector, I was able to simply plug it in and the swap was complete. This cheap, quick fix gave me a brand new battery with more than 50% greater capacity than the original. But I wasn't finished just yet.
Battery Charging Port
One thing that has always bugged me about these little action cameras is that they must be charged via USB. It works okay most of the time, but there is very little feedback. You usually only have a single LED that tells you when the battery is charging and when it's done. I've become accustomed to having much more information when charging the various LiPo batteries that power my RC models. So I decided to add a charging port to my Mobius that would allow me to ditch the USB cable and charge the battery with a dedicated LiPo charger.
I should preface this section by telling you that this task is only for those who have the knowledge and equipment to properly charge LiPo batteries. These batteries demand gentle handling and a healthy respect. You also need to be comfortable soldering fairly small components.
I didn't come up with the idea of using a charging port. There are several videos on YouTube that show how it's done--or rather, how it could be done. The examples that I saw have an add-on battery connector protruding from the case attached to a length of wire. I'm sure that method works fine, but I was concerned that a dangling bits might be in the way or get damaged when mounting the camera to a model. I took a different approach by adding a flush-mounted female charging port on the side of the camera case…no dangling bits.
The stock power plug on the battery is a JST Micro 1.25. It is an itty-bitty plug that is also used on several brands of tiny RC models. This plug is fine for the Mobius where there is very little electrical current and the plug is rarely disconnected. However, this plug has a reputation of wearing out quickly in applications that involve frequent mate/disconnect cycles. So it just wouldn't do for my add-on charging lead. I upgraded to the JST-PH 2.0, a slightly larger connector that is considerably more robust.
I found an area on the case of the Mobius that could accommodate a flush-mounted female 2.0 plug. The Mobius case is pretty soft, so I was able to cut out a notch for the plug using an X-Acto knife. I removed the battery from the case and connected the plug using 26-gauge stranded wire. Pay special attention to polarity when making your connections.
The battery has an integrated circuit board connected to the outputs. Honestly, I'm not exactly sure what purpose(s) it serves here. Most of the time, these micro-boards on LiPo cells manage voltage and current to protect the cell from overcharge, over-discharge, or excessive amp draw. I wasn't sure if the board would impact my charging functions. As a test, I connected my charge wires to the output side of the board (same as the stock power leads). The battery has been charging normally, so, I'll keep the wires there. Alternately, you could bypass the board and connect the charge leads directly to the battery tabs.
After the battery was returned to the camera case, I tacked the female connector into the cutout using thick CA glue. Although both sides of the case are notched, the plug is glued to only the bottom half. I strengthened the plug-to-case glue joint by making a fillet of GOOP around the edge.
My LiPo chargers also use female JST-PH 2.0 plugs. I made a few male-to-male adapters that allow me to connect a charger to the camera's charge port. Some applications out there use JST plugs configured with opposite polarity. So, I double-checked the polarity of the entire charge circuit before applying power for the first time.
The 2.0 plugs have spacing very similar to the pins on my LiPo voltage monitor. With gentle persuasion, I can connect a monitor to the camera and quickly determine the charge state of its battery.
Only after completing the installation did I snap to the realization that the female plug I had hardwired to the battery has both electrical contacts somewhat exposed. I could imagine a screwdriver or Allen wrench sliding around in my flight box and finding just the right angle to short out the contacts. That could be a bad day! To prevent this scenario, I removed the contacts from a male plug and sealed the open ends with liquid electrical tape. This protective plug stays in place whenever the charge port is not in use. Unfortunately, it protrudes a little more than I'd like.
Overall I've been very happy with the increased battery control that the charge port provides. In fact, I added similar ports to my other Mobius and my Foxeer Legend. The plug was a tight fit in the Legend case!
I chose the standard lens (86-degree field of view) when I bought my first Mobius. In fact, I don't know if there was a choice of lenses at that point. But I do know that the first camera saw very little use once I bought my second Mobius with a wide-angle lens (116-degree FOV). I'm sure that the standard lens is great for several applications. For the shooting that I do, however, the wide-angle lens is best.
The good news here is that the lenses are interchangeable. You can buy an entire lens module that includes the sensor for $31 to $37, depending on which lens you want. In this case, you remove your current lens module, slide the new unit in place, and connect the ribbon cable. In only a few minutes, bada-bing, you've got a new lens.
I took the more economical route and purchased a standalone lens for $25. I was happy to see that the Mobius now has an even wider angle 132-degree FOV lens. That's the one I chose. Installing this unit is nearly as easy as swapping out the entire module. You just have to invest a few minutes getting the lens focused as well.
The lens is threaded into the sensor housing. A tiny setscrew prevents the lens from rotating. I loosened the setscrew and removed the standard lens. I then screwed the new wide-angle lens into the sensor housing. The case has two slots for the sensor housing. It is necessary to move the housing to the forward location when switching to a wide-angle lens. The housing fits into place with a gentle friction fit.
I utilized the Mobius' live video output to get the new lens focused. A Mobius FPV cable piped the video signal to one of my FPV video transmitters (VTX). With that connection made, all I had to do was tune my Tactic FPV-RM1 7-inch monitor to the signal. You can omit the VTX and hardwire the output directly as long as you have the correct cables and adapters. It doesn't matter how you do it. The point is simply to get the camera's live feed on a decent screen.
Since most of my shots include parts of an airplane that are really close, I pointed the camera at an object on the wall about 3 feet away. I threaded the lens into the sensor housing until the image came into focus. It took a few back and forth adjustments until I was satisfied and tightened the setscrew. I may make further focus adjustments once I am able to fly with this camera and review the footage.
The final step in the lens swap was to update the camera's firmware to reflect the new lens. This was easily done in the Mobius interface program on my PC.
More to Come
It feels good to finally get my underutilized action cameras back into the mix. I have a few projects coming up that will be ideal for these revived units. And now that I'm in a camera-tweaking mood, I just may get around to investigating that pesky black spot on all of my GoPro videos. I also need to figure out a better way to charge the batteries for my RunCam 2. You'll see it here if I make any progress on either front.
Terry is a freelance writer living in Buffalo, NY. Visit his website at TerryDunn.org and follow him on Twitter and Facebook. You can also hear Terry talk about RC hobbies as one of the hosts of the RC Roundtable podcast.