Deep sleep question for Underwater camera

Official Hardware Nano Family Classic Nano
1

I need some advice regarding maximizing battery time. First the background. I’ve built an undewater camera system that allows to me to see what’s going on in my crab traps from a remote (dry and warm) location. When I see there’s crabs in the trap I row out and get them. The batteries in the system last about 24 hours. However 10 to 12 hours are at night.
The camera and FPV (drone) transmitter are powered by a 12v battery pack. As I only check the trap every few hours I don’t need the camera/transmitter on all the time – it would drain the batteries in no time. So I turn on and off the camera/transmitter with a relay controlled from the cabin. The simple on/off relay is controlled by an Arduino nano attached to a Lora transmitter. The Nano is controlled from the 12v battery back though a 5v stepdown. The Lora’s 3v input is supplied from the Nano.

What I’d like to do is basically shutdown as much battery drain during the night – say from 8pm to 8am. Then at 8am the system wakes up.

I could use a light control relay, but during the summer (when I use the system) there is often only 7 or 8 hours of darkness ( 10:00pm to 5:00am). I would also have to power the relay system so I’m not sure how much net power I would be saving. Another possibility is to use a simple on off alarm powered by a DS3231 clock unit that would cut off the power to the Lora transmitter. That would save some power.
However the final suggestion would be to put the Nano into deep sleep (with the DS3231). Since the Lora Transmitter receives it’s power from the Nano I’m ASSUMING that power would be cutoff when the Nano goes into deep sleep.

So, I’m asking for opinions which system would be best and if anyone out there have any sketch examples I could use to put the Nano to sleep at a given time and wake it up at a given time.

Thanks.

2

No, absolutly not.

Whilst a device attached to the Nano, may be connected to the Nano supply pins, this does not mean that putting the Nano to sleep cuts of the supply to other devices, or puts them to sleep.

3

I have used the following low power/sleep library with great success;

Also, you may get some useful tips reading through the underwater arduino data logger website at:

The section " How to Build an Arduino Data Logger" is well worth a read.

4

You could use a Pololu Power Switch to control the power to other devices. The Nano would shut that off before going to sleep, then turn in on again.

5

Thanks for taking the time to consider my problem. Hadn’t heard of a pololou switch before. However its seems it’s a sophisticated relay. I still need some advice on the main problem of figuring out the programming to use to set a sleep and wake function for the nano.

Best

Jeff

6

Just use one of the low power libraries, like that linked above. Start by studying the docs and examples that come with it. Very simple to use.

7

Nice to hear from you again. I was afraid of that. So that means the program(s) needs to shut off power to the lora first (probably another relay) then put itself to sleep.

8

You do not want to use a relay in a low power device.

9

Hey Mark, this looks very promising! Thanks for putting me on to ie.
Jeff

10

You need to use code, normally provided in the LoRa library you are using, to put the device to sleep. Most LoRa modules have a sub 1uA sleep current.

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Thanks for all who reached out with advice. It's much appreciated. After considering that I would have to design sleep cutoffs for BOTH the arduino and Lora I've decided that the simplest solution will be to go to the photorelay switch which will run off the main battery system and cutoff voltage to the arduino/lora at night. Although it won't put the system to sleep for 12 hours, the net energy loss will probably be about the same.

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