Quick weatherproof camera box. - page 8 - Hotwire! Hardware Mods, Accessories and Insights - CHDK Forum

Quick weatherproof camera box.

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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #70 on: 05 / September / 2013, 17:11:39 »
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By the way, I noticed that All-Battery.com has the perfect circuits for battery protection. So I was interesting in buying there, untill I noticed that shipping to Norway cost a whopping $100! I searched eBay but no luck. Do you know anywhere else they sell these kinds of battery protections?

Ebay is awash with that kind of thing. These are the same boards that are fitted to a lot of 18650 based devices.
Try this search.

This looks to be a pretty standard part.

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Offline JvdP

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Re: Quick weatherproof camera box.
« Reply #71 on: 05 / September / 2013, 17:16:24 »
Ebay is awash with that kind of thing. These are the same boards that are fitted to a lot of 18650 based devices.
Try this search.

This looks to be a pretty standard part.
Thanks. I found out this guy called hunk_lee has a good collection. Interesting name. :D

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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #72 on: 05 / September / 2013, 18:38:36 »
@JvdP Some of those little protection boards could be easily re-purposed as electronic battery switch modules. They generally contain all you need, to switch your cells on and off with a microcontroller, i.e. suitably rated mosfets pre-soldered to an easy to work with PCB.

They would need a few components removing or replacing, but much easier to work with than designing from scratch.... I think you just got my old grey cells firing again... 

Mr Hunk-lee has a more promising sounding name than "Quick Fire" LiPo batteries, or anything remotely electronic sold by Mr Bang Good. (I am not making these up BTW, both "Quick Fire" and "Bang Good" are genuine). 
« Last Edit: 06 / September / 2013, 09:36:09 by ahull »

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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #73 on: 06 / September / 2013, 10:25:58 »
I am aware this thread has gone a little off course and developed a heavy "Solar Charger" feel, but hopefully it will be back on course soon.

Meanwhile here is another "Solar Charger" observation, albeit a not very interesting one, this time about charging the device.

While charging using the USB input, the output of the "Gold Solar Charger 2600mAh" battery slowly increases till it hits the maximum charge voltage of the LiPo (around 4.2V at which point the LiPo is fully charged), then something unexpected occurs.

The LiPo charge protection switches out the battery, as it is designed to do, because LiPo cells don't like over voltage, and cant be trickle charged. At this point, we see a sudden *increase* in output voltage.

Within the space of  less than a second the output goes from 4.24V to 4.71V, the reason so far as I can tell is that since we no longer have the battery in the circuit, we are now connected directly to the USB charger +5V source via one schottky diode drop.

This would of course mean that if you left the camera running and attached to the nominally 3.7V output it could potentially be fed up to as much as 4.8V, but perhaps more importantly if the charger was unable to provide enough current to run the camera, then the charger might suddenly shut down (or worse still an internal protection fuse might pop in your charger, bear in mind that some USB +5V chargers are limited to 500mA or less, so there is a pretty high chance of this).

If the charger did switch off rapidly, this should simply result in the battery kicking back in, but it would also probably cause a fairly abrupt transient spike and or dip in the supply, perhaps enough to crash the camera or maybe cause it to shut down unexpectedly. 

This problem would also  affect any purely  "solar panel connected to a LiPo" setup, and probably  it would be worse, since the panel is not going to have a nice clean steady +5V, and furthermore it would be unlikely to be able to drive the camera directly (unless it was a whopping big panel).

We have a situation where once fully charged the LiPo and solar panel could start to oscillate on load, with the battery switching out, the load transferring to the panel, the panel overloading, the battery switching back in and so forth.

I suspect therefore it would be a good idea to add a  suitable smoothing capacitor across the input to the camera to avoid potential issues. Furthermore if your solar panel is capable of producing much more than +5v in direct sunlight you would have to feed the battery charger through a regulator, or we are back to fighting with the magic smoke.



Two completely unnecessary pictures of my multimeter and some assorted clutter.
« Last Edit: 06 / September / 2013, 11:07:25 by ahull »

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Offline JvdP

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Re: Quick weatherproof camera box.
« Reply #74 on: 06 / September / 2013, 10:31:26 »
Hi ahull, interesting find. Especially since I came across something very similar earlier this week. Please read this experience from a CHDK user while fiddling with the Adafruit LiPo solar charger circuit.

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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #75 on: 06 / September / 2013, 10:53:03 »
It might also explain one rather odd behaviour of this particular type of charger.

Once fully charged, via the USB port,  the charge light goes out. All as you might expect. However if I look closely I  see that the charge LED actually flickers very dimly at a rate of a few Hz. Presumably because the LiPo protection circuit keeps kicking in and out.

I don't have a scope to hand, but I suspect if I connected one I would see a very interesting series of spikes across the output and these are probably what is lighting the charge LED.

The Adafruit solar charger may well behave in the same way, I don't have one to hand to test. It certainly works in a similar fashion, and its output may also exhibit this quirky problem.

EDIT: Actually the post you linked to above refers to bwh13 and the LDO regulator module he is using, not as I mistakenly thought the Adafriut solar charger. Nonetheless, the above observations apply to this setup too. The LiPo will switch off when fully charged with the Adafruit charger or the LDO too, leading to a similar situation.
« Last Edit: 06 / September / 2013, 11:53:38 by ahull »

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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #76 on: 07 / September / 2013, 06:00:23 »
It would seem my cynicism was ill founded, the "Gold Solar Charger 2600mAh" does actually charge the battery with the solar panel. In direct sunlight, I get around 4.46V from the panel on load (i.e. while charging). I wont bore you with another picture of my multimeter, but if you want the proof, it is in the usual place

Furthermore the black version of the charger was drained flat last night and placed in a sunny spot. This morning the charge light is glowing away nicely and has received enough charge in the last couple of hours to be able to at least power up the camera.

Of course the real cynics amongst you will be questioning whether there is such a thing as a sunny spot in Scotland in September, but I assure you its a lovely day here.  :P

Next on the agenda, since I am still missing the mythical mosfets will be testing the capacity of the battery, fed directly to the camera without the two unnecessary regulation stages.
« Last Edit: 07 / September / 2013, 06:06:43 by ahull »

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Offline bwh13

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Re: Quick weatherproof camera box.
« Reply #77 on: 07 / September / 2013, 20:31:06 »
Quote
EDIT: Actually the post you linked to above refers to bwh13 and the LDO regulator module he is using, not as I mistakenly thought the Adafriut solar charger. Nonetheless, the above observations apply to this setup too. The LiPo will switch off when fully charged with the Adafruit charger or the LDO too, leading to a similar situation.

I don't know if there was any confusion surrounding this, but I was using the Adafruit charger and I was seeing the higher voltages when the battery was either charged or getting its max charge current (much like what AHull seems to be reporting.) I had to build the LDO (yet to be tested.) As an alternative while researching the LDO, I found the buck/boost from Pololu and it has been running the camera now for 13 days.

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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #78 on: 08 / September / 2013, 07:19:11 »
The real issue seems to be that there is no provision to allow charging and running the camera at the same time, or to be more exact, we can charge and run the camera at the same time, but the moment the battery is fully charged, the battery protection circuit will kick in and we then end up with the camera connected to the charger.

I am still thinking about the simplest way to deal with this, i.e. to seamlessly switch from on charge to fully charged and charger disconnected, and still have the charger kick back in once we drain the battery to a certain level. We need the equivalent of a battery thermostat, a "voltostat" if you will that lets the battery charge and discharge within a certain range, without ever quite letting the battery completely charge, and thus hitting the voltage where the protection IC to kicks in and takes the battery out of circuit.

In other words, we need to avoid hysteresis, i.e. the oscillations we are seeing where we swap back and forward  between on charge and battery disconnected/charger connected. 

I think I will experiment with a simple large smoothing capacitor, that will at least remove the sudden glitch, and should smooth out the oscillation, albeit that it will still allow the voltage to increase towards the charger/solar panel output voltage. If that doesn't work I need to look at something a little smarter, but let me start with the simple approach first. 

I want to try to avoid adding additional voltage regulation if I can, (i.e. using the buck/boost regulator you describe) to keep the losses down, and also avoid any more diode drops as I don't want to limit the available useful voltage curve from the battery. I suspect though that regulating the charger input to say 4.1V my be the only simple solution. If so, I might look at tweaking one of those buck/boost converters to see if we can make it more efficient at the low voltage levels we are using.

I also thought of crowbarring the charger/solar panel with a 4v1 zener diode... as well as the smoothing capacitor, but this is a little crude, would probably not work and may well stress the solar panel. 
« Last Edit: 08 / September / 2013, 07:42:50 by ahull »

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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #79 on: 08 / September / 2013, 16:25:51 »
The "Gold Solar Charger 2600mAh" is back in the singularity containment field on the old dinner plate for tonight's discharge experiment.

This time I have rigged up the camera directly to the LiPo output, i.e. the safe side of the LiPo charger circuit through an XT60 plug/socket and the dummy battery.

The battery was fully charged till the protection circuit kicked in, the USB charger was disconnected and then the XT60 side was connected immediately to the camera. Now we have no excuses for poor performance. If the battery fails to live up to expectations, its because its a squib like we suspected.  Barring any mishaps, including the implosion of the local galactic sector, I should have the results in the morning (possibly sooner given its previous dismal performance).

Don't panic, and sleep tight. My money is on the plate holding out without any trouble.  :P
« Last Edit: 08 / September / 2013, 16:33:15 by ahull »

 

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