Mini0806: Peculiar behavior under low battery condition.

SergeiF

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Hi (specifically Rayman@MegTech):

Between me and my friends we have 5 mini0806 cameras (6 if you count the one on the way back to gearbest). I personally have two. So far the failure rate is 1 out of 3.
In the most recent fix, I replaced the battery (as the camera was crashing during power transitions).
After replacing battery the camera was still misbehaving.
So I have added a 470uF cap after the big Schottky diode to remove whatever ripple the crappy 5V adaptor outputs and noise from pogo pins bouncing on the connector (I noticed these pogo pins were unreliable on gravel road).
When I was adding the capacitor I measured the voltage of the battery. It was around 2.7V(!). This brings to the subject of this thread: mini0806 and low battery voltage.

What I observed I consider a serious design defect: mini0806 does not have low (3.2V) battery cut-off. It will happily discharge the battery until the little PWM module that supplies the ARM chip stops working, which according the specs of the module used is around 2.8V. Guess what happens when the voltage gets near that value? The SoC crashes and is left in ON state (while getting quite hot, basically implementing Halt and Catch Fire).

So here is the scenario of perpetual battery death and camera crash:

1) Short trips or long storage time will cause the battery to be relatively low.
2) After a short trip, not enough to recharge battery, the battery voltage drops to a level where camera crashes. This crash instead of powering down safely, or instantly, will cause the SoC to stay on (in crashed state - red light permanently on) until battery voltage drops to below 2.7V.
2a) if next power up happens before complete depletion, the camera will remain in crashed state (not sure if it will charge or not). This is bad because at this stage it will not record.
3) If there are no sufficient long trips, the camera will never shut down properly and will kill the battery very fast (repeat point 2).

If the camera is stuck in the crash loop (where it never shuts down gracefully), the only fix is to 20sec power off (depending on the battery level will or will not work), or let it die, and then charge it up from the wall USB charger for at least 30min.

The proper fix is to add low voltage cut off (independent from SoC).

Show stopping flaws of these cameras are (or how to make mini0806 better, not in particular order):
1) No low voltage cut-off for battery (this can be achieve with battery protection chip or couple transistors).
2) No reset button (eg: battery disconnect momentary NC push button would be a simple solution).
3) Poor voltage regulation circuits (no large smoothing caps?). The 0.5V over voltage tolerance of the PWM chip is way too low (at least add a beefy 5.4V zener to deal with transients). The Camera relies too much on 5V supply being smooth, noise and transient free. No such thing with crappy buck-down/switch mode converters shoved inside of a cigarette lighter adaptor.
4) Recording file cut off in the middle leads to completely unusable file (instead of recoverable corruption). The solution is to sync (flush buffers) every I frame not at the end of the file. Who cares about the the SD card life after an accident?
5) The crappy pogo stick connector - seriously, what is wrong with just using TRRS connector? Make camera mount out of solid metal, and have a flexible wire with 3.5mm TRRS connector connecting the camera from the base (GND EN, TX, 5V).
5a) Crappy mount: the camera sags a bit from its own weight, making video on slight lean, and vibration apparent.
6) Crappy flexible wire connecting the camera board to the rotating connector. The TRRS plug would remove the necessity of such wire and reducing assembly costs (and RMA from improper assembly, jamming and damaging the wire).
7) Crappy 40'C rated battery in an environment that sees 80'C frequently. Add second standby supply (always on) to bypass the battery entirely (with supercap as backup). Maybe allow the second micro usb feed to act as standby feed via firmware setting?
8) Atrocious firmware. The SD card switching does not work, which is much more important than LDWS (LDWS is utterly useless). It is ~5 lines of code to implement the SD card switching logic. The undocumented storage of GPS/Accelerometer data as subtitles is nice, but why the hell the speed is in MPH (it should match the whatever is configured on camera)? The flip-flopping of the timezone setting between firmware versions does not inspire confidence in quality of the firmware.

In conclusion I decided to not buy anymore mini products (sorry Rayman, it has been a pleasure dealing with you, but product hasn't been tested properly). Instead I will wait for good A12 based cameras and find the most stable one with least features.
 
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