(help) Dash camera UPS

[robotic]

Hi everyone,

I bought a dash cam a while back and am not complete sure what is wrong with it.   I'm thinking the internal battery is out of most of it's power or something.  It works when I turn on the car and the time and date are always right when I start up the car.  However, it use to turn off after a couple of seconds and properly power down so my last file would not be corrupt.   Now after I shut off the car it pretty much just shuts down immediately and the last file is always corrupt.

To solve this, I was thinking of creating a  dashcam ups connected to my car 5v ->  dashcam ups -> dash camera

So the dashcam ups bypass will just feed 5v to the dash camera and when the  dashcam ups notices that it is not being powered it will count 2 minutes and then turn off.  This will let the dash camera finish it's 3 minute write cycle and the last file will be saved.

Now I'm not too sure how to make this...  I know I will need
- some kind of timer (I thought it would just be easier if I use a digispark or arduino) 
- A way to sense voltage coming from car usb port to tell when there is no more power
- A way to switch to battery mode if power is cut off from the car
- A 3.7v battery as a power source for the 2 minutes.
- A charging circuit for the 3.7v battery.  I'm hoping for it to charge the  dashcam ups's battery as well as passthrough the 5v to the dash camera at the same time.

Any help would be appreciated.  This dash camera has sadly(because I had accidents)/luckily saved me from he said she said arguments from a couple of accidents.

Thanks

[paulca]

Been looking down this road for a while myself.

https://www.eevblog.com/forum/beginners/battery-float-with-current-limiter/msg1331637/#msg1331637

The short answer is.  It's not going to be easy.  Most of the easy options have "gotchas".

If you are willing to spend money there are a few commercial options, but they cost between £180 and £300.

As to the last file being corrupted, it "could" be the super capacitor within it has dried out or failed in the heat of the sun stuck in the window constantly.  The powering down within a few seconds is perfectly normal, but the corrupt file is not.

Note that you do get the odd corrupt file due to the dash cams not properly implementing the error detection and sector marking which should be used for SSD cards.

My use case is a little bit different than yours.  it seems you only want to power the dash cam for a couple of minutes after the car goes off.

For that you could purchaer single super capacitor and wire it across the two power pins of the dashcam.  Job done.  When the power is on the cap will charge up and supply a smooth 5V (do check it's not 12V which would make more sense in a car).  When the power shuts off the capacitor will discharge slowly.  A LARGE super cap the size of a D Cell battery will probably run the dashcam for 10+ minutes.

[IanMacdonald]

Problem I see here is that even if you extend the shutdown time it will still corrupt the last file when it shuts down. Since that could mean half an hour of recording lost it's not very acceptable.

I feel that having a dashcam on a separate switch is a better idea anyway. There is the the risk of leaving it on overnight but usually that won't case a flat battery.  The draw is about 300mA which means a few Ah overnight at most. The problem with having it on the ignition is that you have to leave the keys in the car to have it stay running at the scene of an incident. That risks having the car stolen.

That risk would certainly arise if you rendered assistance to a crashed vehicle and it turned out that the driver was a criminal. 

[paulca]

The is "Power magic" boxes, for 12V dash cams, which run direct off a non-switched fuse in the car fuse box, 24/7 using the car battery.  They have configurable low voltage cut outs so you should be able to restart the car in the morning.

I personally don't trust these.  My car is notorious for having a weak battery and high leak current at times.  I have left it for a week idle and even after that I could hear the starter motor turn slower.  Don't want to put more fuel on that fire.

http://www.halfords.com/technology/dash-cams/dash-cam-accessories/blackvue-power-magic-pro

Also of note.  Dashcams usually save videos in 3-5min chunks for the exact purpose of preventing loss of larger segments.  The internal capacitor is meant to last long enough for the dashcam to close the current open file and flush the disk buffer.

Note, you read that right, £40 for a low voltage cut off and 555 timer.

[Gregg]

I've been thinking about the same situation, but mostly I'm concerned that someone will smash a window to steal the dash cam so I remove it most of the time.  Anyway I think that a small 12V glassmat lead acid battery powered via a Schottky diode to charge from an ignition on circuit and a battery protection circuit between the small battery and the 5V dash cam power supply to keep from overly discharging the small lead acid battery would be about as simple, cheap and reliable as anything.  Here is a link to an ebay seller of a ready made battery protector module:
https://www.ebay.com/itm/Under-Over-Voltage-Protection-Module-Battery-Automatic-Charger-Discharger-Board/232477980321
You may have to scroll down to review all of the modules offered by this seller.

[paulca]

One thing to consider is the initial charge current when the small lead acid is part depleted.  The car will happily give it 10A if it wants it and (in my case) blow the utility socket fuse.

Small SLAs have different float charge voltages too.  A car battery will happily sit at 14.40V-15V all day, a small SLA will not.

As the OP only needs to run the camera for enough time to end the current video file and start a new one (which will become corrupted), all he needs is a beefy capacitor across the 5V leads.

[robotic]

One thing to consider is the initial charge current when the small lead acid is part depleted.  The car will happily give it 10A if it wants it and (in my case) blow the utility socket fuse.

Small SLAs have different float charge voltages too.  A car battery will happily sit at 14.40V-15V all day, a small SLA will not.

As the OP only needs to run the camera for enough time to end the current video file and start a new one (which will become corrupted), all he needs is a beefy capacitor across the 5V leads.

Yes all I need to the current video to end.  The dashcam records in 3 minute chunks so technically I only need 2m59s.    What is considered a beefy cap?  I bought a couple of small supercaps a whileback maybe I'll test it out if that's all I need and time it for dissipation.  What would be approx. F? I'm not sure the draw I'm guessing 200mah.  I'm assuming 20F @ 5V

Power is drawn from an usb adapter connected to the cigarette lighter. So not hard wired into the 12V system

[suicidaleggroll]

One thing to consider is the initial charge current when the small lead acid is part depleted.  The car will happily give it 10A if it wants it and (in my case) blow the utility socket fuse.

Small SLAs have different float charge voltages too.  A car battery will happily sit at 14.40V-15V all day, a small SLA will not.

As the OP only needs to run the camera for enough time to end the current video file and start a new one (which will become corrupted), all he needs is a beefy capacitor across the 5V leads.

Yes all I need to the current video to end.  The dashcam records in 3 minute chunks so technically I only need 2m59s.    What is considered a beefy cap?  I bought a couple of small supercaps a whileback maybe I'll test it out if that's all I need and time it for dissipation.  What would be approx. F? I'm not sure the draw I'm guessing 200ma min

Power is drawn from an usb adapter connected to the cigarette lighter. So not hard wired into the 12V system

The camera expects a 5V input, let's assume it can operate down to 4.5V before having issues.  It likely draws a watt or more as well.  So this capacitor would need to supply at least 1W for at least 3 minutes while only allowing the voltage to drop from 5 to 4.5V.  That would require nearly 100F.  You're well into series-connected and balanced/protected supercap territory there.  There's also the issue of it discharging back into the switched off DC/DC converter, possibly damaging it or discharging the cap prematurely.  You could use a diode to keep the current from reversing, but then you lose your 0.5V discharge room.  There's also the issue of the minutes-long current surge when powering this on, which would certainly send the DC/DC converter into overcurrent shutdown.  Far simpler to use a battery IMO.

Of course the simplest option is to just open up the camera and replace the internal battery.

[robotic]

One thing to consider is the initial charge current when the small lead acid is part depleted.  The car will happily give it 10A if it wants it and (in my case) blow the utility socket fuse.

Small SLAs have different float charge voltages too.  A car battery will happily sit at 14.40V-15V all day, a small SLA will not.

As the OP only needs to run the camera for enough time to end the current video file and start a new one (which will become corrupted), all he needs is a beefy capacitor across the 5V leads.

Yes all I need to the current video to end.  The dashcam records in 3 minute chunks so technically I only need 2m59s.    What is considered a beefy cap?  I bought a couple of small supercaps a whileback maybe I'll test it out if that's all I need and time it for dissipation.  What would be approx. F? I'm not sure the draw I'm guessing 200ma min

Power is drawn from an usb adapter connected to the cigarette lighter. So not hard wired into the 12V system

The camera expects a 5V input, let's assume it can operate down to 4.5V before having issues.  It likely draws a watt or more as well.  So this capacitor would need to supply at least 1W for at least 3 minutes while only allowing the voltage to drop from 5 to 4.5V.  That would require nearly 100F.  You're well into series-connected and balanced/protected supercap territory there.  There's also the issue of it discharging back into the switched off DC/DC converter, possibly damaging it or discharging the cap prematurely.  You could use a diode to keep the current from reversing, but then you lose your 0.5V discharge room.  There's also the issue of the minutes-long current surge when powering this on, which would certainly send the DC/DC converter into overcurrent shutdown.  Far simpler to use a battery IMO.

Of course the simplest option is to just open up the camera and replace the internal battery.

Yeah I thought about that as well.  Last time I opened it up, I broke it somehow... Not sure if it was already broken and I just couldn't fix it by adding a new battery or what.  Probably the latter.   Sounds like too much of a problem to do supercap.  I forgot about voltage drain.  Doing the ups may also help with future projects or as an emergency solution.  I would like to pursue it I think.

[robotic]

Yeah it is probably the battery like I said in my previous post.  It surprisingly still keeps time though after a few days, so I know the battery isn't completely dead anyways.

I still want to work on it, just as a nice project as well as if I do ever need something like this because it does seem useful to have a ups type device to turn off things after a certain amount of time.

I found an article using FQP30N06L for a ups.  That might work for 1 part in which it triggers the dashcam off.

powerA = car
powerB = ups

So if powerA is providing power turn on FQP30N06L [dashcam will turn on]
if powerA is not providing power, start timer for 3 minutes, turn off FQP30N06L.

I'm not sure how to bypass powerA and use powerB when powerA is interrupted (car engine off).

[paulca]

It's likely the cam is powered by a super cap inside it.  Which (should) provide enough power to give it a few seconds to close the file it's currently saving when it detects a loss of input power.  This is how mine (BlackVue) works.

If you have dislodged that cap or broken it some other way then the camera will power down instantly when you disconnect the power and corrupt the last file and potentially the SD card filesystem.

Currently when you disconnect the power does the dash cam indicator lights remain on for a few seconds and then fade out or does it just switch off instantly?

Mine even has enough time/power to audibly say "BlackVue shutting down"

There are many cheap and nasty dash cams.  How sure are you that the one you have did save it's last file without corruption previously?

[robotic]

It's likely the cam is powered by a super cap inside it.  Which (should) provide enough power to give it a few seconds to close the file it's currently saving when it detects a loss of input power.  This is how mine (BlackVue) works.

If you have dislodged that cap or broken it some other way then the camera will power down instantly when you disconnect the power and corrupt the last file and potentially the SD card filesystem.

Currently when you disconnect the power does the dash cam indicator lights remain on for a few seconds and then fade out or does it just switch off instantly?

Mine even has enough time/power to audibly say "BlackVue shutting down"

There are many cheap and nasty dash cams.  How sure are you that the one you have did save it's last file without corruption previously?

Mine doesn't shutdown immediately it waits about 2 seconds but requires about 5-8 seconds to properly shutdown (triggering the shutdown when not connected to power.  I'm pretty sure it's a lipo battery inside and I know the battery isn't completely disconnected or I would not have any time/date.

Anyways, I'm more interested in building the UPS.  I may change the battery in the future and have talked about this in earlier posts.  Thanks anyways.

[paulca]

I wonder if you could hack a USB power bank for this purpose.  The one I have will not output AND charge at the same time though maybe they exist were they will.

This might give you ideas: http://www.theoutpost.org/6-techy/raspberry-pi-usb-power-bank-ups-pass-through/

[robotic]

I wonder if you could hack a USB power bank for this purpose.  The one I have will not output AND charge at the same time though maybe they exist were they will.

This might give you ideas: http://www.theoutpost.org/6-techy/raspberry-pi-usb-power-bank-ups-pass-through/

I bought a couple of powerbank modules and that was actually one of my ideas.  Once I get the logic transistor chip I will probably test it out.