Voltage protection by Blue Pill in time lapse rig

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Sdack
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Voltage protection by Blue Pill in time lapse rig

Post by Sdack » Thu Oct 26, 2017 7:58 pm

Hi,
I am a total novice, planning to use a Blue Pill as an intervalometer, controlling the power to a time lapse rig consisting of a Canon point and shoot camera (using the CHDK - Canon Hackers Development Kit), and a Raspberry Pi.

The power for this remote placed rig will likely come from a cheap, chinese, 6 LiPo battery pack

Image

https://www.ebay.com.au/itm/121957836096

which can output either of the two voltages I need for the components ie. 3.7v for the camera and 5v for the Raspberry Pi. I plan to buy the safest chemistry Lithium Iron Phosphate (LiFePO4) batteries for the pack. Can anyone suggest the most efficient method for boosting the 3.7v up to 5v, so I can power both devices at the same time, or perhaps regulating down the 5v output to 3.7? I've read that linear regulators are wasteful in heating up while buck converters are pretty good. Is boosting a voltage up more wasteful than regulating a voltage down?

I'm hoping I can add power measurement to the BluePill sketch such that it will sense when the power pack is getting near the low threshold for safety and stop the power supply. Is this even possible and could someone link me to some tutorial or a sample sketch?

Thanks in advance
Sdack

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ahull
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Re: Voltage protection by Blue Pill in time lapse rig

Post by ahull » Thu Oct 26, 2017 10:26 pm

I simply used one of the cheap LM2596 buck regulator modules that litter ebay. (I think generally that buck tends to be more efficient than boost conversion, and both are more efficient than linear regulators).

Image

Bunch of pictures here -> https://plus.google.com/u/0/photos/1110 ... 6731304017
- Andy Hull -

Sdack
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Re: Voltage protection by Blue Pill in time lapse rig

Post by Sdack » Fri Oct 27, 2017 2:12 am

Thanks Andy,

I just ordered a couple of those LM2596 buck converters.

Originally I misunderstood the ebay item as being able to 'simultaneously' output the two voltages, but that's ok.

I pm'd you on the CHDK forum, hope that's ok. I'm very excited about my time laspse adventures, since getting a nice result yesterday morning in my neighbour's field.

https://www.vimeo.com/239930114

Best wishes

N

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ahull
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Re: Voltage protection by Blue Pill in time lapse rig

Post by ahull » Fri Oct 27, 2017 9:21 am

Hi, hope you don't mind if I post your CHDK PM here.
Hi Andy,
The parts for my extended, internet connected, time lapse rig are arriving bit by bit on the slow boat finally.

I did think rather than a PM, I should start a thread for this but I'm not sure where to put it. If you advise, I'll transfer it to an appropriate place in the forum.

I have been reading up yours and other folks DIY 18650 power packs and have decided it seems the best way to go, so I've ordered one of these units:
Image


ebay link here
https://www.ebay.com.au/itm/121957836096

I plan to go with the safest battery type I can find, which seem to be the Li-phosphate chemistry, which I read, doesn't burn when exposed to air (if punctured) - http://batteryuniversity.com/learn/arti ... _batteries

Aside from overloading the batteries on recharge, which comes down to the quality of the charger, the issue seems to be making sure they don't drop below their lower voltage safety limit, I read, I think in one of your posts, that because Canon point and shoots, shut down themselves, when the voltage isn't high enough, that provides a secondary level of safety, beyond whatever protection circuitry there may be in the cheap power pack itself.

The reason I chose this model was because it offers both 3.6v AND 5v outputs, which are the desired voltages for the Canon AND my Raspberry Pi controller that handles the internet upload of images. Because the Blue Pill STM32 microcontroller will be powering up the Raspberry Pi I'm wondering if there's some way to add, voltage detection, to the Arduino sketch, so that it will cease when the voltage approaches the lower safety threshold? I'm not yet familiar enough with the capabilities of the STM. Should I post on the STM forum too?

I just read in this thread https://chdk.setepontos.com/index.php?topic=12749.0 in the final post by Axman,

Quote

Lessons learned so far: (some seen elsewhere in this forum, and some learned from burnt fingers)

Try to mimic cam's functions when operated by a human more closely (use the on-off sw if possible).
Affix wires to their final locations before attempting to solder tiny wires to paper-thin switch contacts.
Try not to get it too hot - obviously.
Don't over-voltage - give the cam close to what it expects but not more - kind of obvious..
if possible, leave the power On inside the battery house throughout a day's cycling,
rather than cutting power each time -
the resulting power switch on-off action seems more reliable.


This and the fact that the power button on my Ixus160 seems very small with little movement, makes me wonder whether I could leave the camera on during the shooting day (construction - 8.30 am - 4.30 pm ish). Do you know if there are any figures for the power draw in a low power state, or if there even is such a thing?

Finally, do you think I'm taking too much of a risk with this chinese unit? Can you recommend any other, easily implemented safety features I can put in place to avoid the kind of fireworks I've seen on YouTube?

Cheers
Nigel
First point last. "do you think I'm taking too much of a risk with this chinese unit?" ... not really, these units are probably no better or worse than the sort of thing you get in Asda/Tesco/Wallmart or wherever. They are what they are. So long as you keep them dry and don't let the lipos get too cold (< -18C) or too hot (> +40C) then you should be fine.

So far as the power button on the camera is concerned, I would avoid surgery if possible.
I would tape down the camera power button, as it should then power up automatically when you apply the power through the dummy battery.
Do you know if there are any figures for the power draw in a low power state, or if there even is such a thing?
Search the CHDK forum, I'm sure there is a thread that does in to this in some detail.
I did think rather than a PM, I should start a thread for this but I'm not sure where to put it.
Put it in the "Hotwire! Hardware Mods, Accessories and Insights" section of the CHDK forum. I'm sure a lot of people would be interested, and willing to contribute their experiences.

I am in the process of moving house at the moment, so my apologies if I am as responsive as I usually am for the next few weeks.
- Andy Hull -

arpruss
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Re: Voltage protection by Blue Pill in time lapse rig

Post by arpruss » Mon Oct 30, 2017 3:12 pm

ahull wrote:
Fri Oct 27, 2017 9:21 am
First point last. "do you think I'm taking too much of a risk with this chinese unit?" ... not really, these units are probably no better or worse than the sort of thing you get in Asda/Tesco/Wallmart or wherever. They are what they are. So long as you keep them dry and don't let the lipos get too cold (< -18C) or too hot (> +40C) then you should be fine.
Is 40C really the cut-off for these lipo packs? Eek. Can't use them in the summer around here, then.

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RogerClark
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Re: Voltage protection by Blue Pill in time lapse rig

Post by RogerClark » Mon Oct 30, 2017 8:16 pm

Same here...

We've had some days above 45 deg last year.

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ahull
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Re: Voltage protection by Blue Pill in time lapse rig

Post by ahull » Mon Oct 30, 2017 8:47 pm

I think they will still work beyond these extremes, but their capacity will be affected.
Particularly charging at elevated temperatures >45C, and below freezing may be a problem.

http://batteryuniversity.com/index.php/ ... mperatures
- Andy Hull -

arpruss
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Re: Voltage protection by Blue Pill in time lapse rig

Post by arpruss » Tue Oct 31, 2017 3:33 pm

ahull wrote:
Mon Oct 30, 2017 8:47 pm
I think they will still work beyond these extremes, but their capacity will be affected.
Particularly charging at elevated temperatures >45C, and below freezing may be a problem.
Good to know. Fortunately, I don't charge batteries (except car batteries) outdoors.

Sdack
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Re: Voltage protection by Blue Pill in time lapse rig

Post by Sdack » Fri Nov 10, 2017 4:50 am

ahull wrote:
Fri Oct 27, 2017 9:21 am
Hi, hope you don't mind if I post your CHDK PM here.
Not at all.. thanks for that

The below item arrived and seems reasonably sturdy.. I'm not quite game for a teardown.. might not get it back together again!

Image

ebay link here
https://www.ebay.com.au/itm/121957836096
I plan to go with the safest battery type I can find, which seem to be the Li-phosphate chemistry, which I read, doesn't burn when exposed to air (if punctured) - http://batteryuniversity.com/learn/arti ... _batteries
scratch that.. I decided to go with a local (ie. Australian), supplier and a brand name batteries which came up on special a couple of days ago..

Genuine LG HE4 2500mah 20A Lithium Rechargeable battery

https://www.techaroundyou.com/Vape-Batt ... upply-bulk

and a 6 slot charger to go with the 6 batteries

https://www.techaroundyou.com/Chargers/ ... CD-Charger

Total cost AUD $95, which seems a lot but the charger was $55 of that and the batteries only cost 6.50 each. I went for 'high drain' ones having read they're more capable. Even though there were some 2600mah 30A Sony's available for only a dollar more each.

https://www.techaroundyou.com/Genuine-V ... upply-bulk
I am in the process of moving house at the moment, so my apologies if I am as responsive as I usually am for the next few weeks.
Hope your move went well.. it can be quite unsettling hey!

Cheers
Sdack

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RogerClark
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Re: Voltage protection by Blue Pill in time lapse rig

Post by RogerClark » Fri Nov 10, 2017 6:10 am

If you can put up with 2000mAH batteries you can get a whole single sell power bank from KMart for $7

I suspect you can possibly get them a little cheaper elsewhere.

The batteries in the KMart power bank are labelled "Great Power", which sounds like a Chinese brand.
and have a manufactuing date on them of 20170522 as well as the max charge voltage

I've not tested yet to confirm the capacity is whats written on them.

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