solar panel

[jerabaul29]

I think the Artemis RedBoard Nano should be very easy to use with a LiPo battery + solar panel (6V max) in cases the deployment takes place in an area with lots of sun. I asked on SF GH repo, crossing fingers to get an answer (otherwise may ask on their forum): https://github.com/sparkfun/RedBoard_Artemis_Nano/issues/4 .

Resources (added by gaute):

• https://learn.adafruit.com/li-ion-and-lipoly-batteries
• https://batteryuniversity.com/article/bu-302-series-and-parallel-battery-configurations

[gauteh]

👍 for the sfy power is provided through the notecarrier, it also has lipo charger (or comes in variants with that). I'm wondering if the supercaps need to be downstream the voltage regulator so that they don't interfere with the charger?

[jerabaul29]

Not sure about the supercaps location. We can chat about it :) .

[gauteh]

https://www.adafruit.com/product/4755 think I need something like this, with supercaps placed after load. The sfy uses about 50 mA at 4.5V on average now - but I think that can be improved.

[gauteh]

Maybe @akkermei has some suggestions.

[jerabaul29]

It is common with 6V 1-2W solar panels, this is quite small solar panels actually, and this should be more than enough in theory to drive the sfy? :) But agree 50mA average sounds like a lot - in pure ISM330DHCX logging + on the fly Kalman filtering, power use on the OMB is typically a couple of mA if I remember correctly. Even with the occasional modem spikes, 50mA sounds like quite a bit.

[jerabaul29]

Edit: 8mA in wave measurement mode for the OMB; but I think this is more than strictly needed, think there is 1 LED on the qwiic switch that remains active, + the artemis is in burst mode so double the power usage, + possibly some other wastes.

[gauteh]

Solar panels:

• https://www.sparkfun.com/products/18726 IP67 / 1.2W

maybe 2 or 3 for SFY, maybe enough with 1 for OMB?

@jerabaul29 : students will be working on this this summer. it would be great if we can do some work that both benefits OMB and SFY. I'm setting up a shopping list, please take a look and suggest setup if you have time. Will order somewhen next week so no rush.

[gauteh]

Related: #124

[jerabaul29]

Regarding the OMB, "everything" needed regarding "electronics infrastructure for using solar + battery" should already be provided by the AGT, i.e. the AGT has solar power connector + battery connector + "battery solar charger" to make sure the battery does not get overcharged etc.

A few notes, of course all of this would need testing:

• since the OMB uses very little power, it should in theory be more than enough to include for example one such solar panel on top of it, looking directly up (that would fit on top of the OMB with good margin): https://www.sparkfun.com/products/18726 . It could even be possible to fit 2 on top of the OMB if needed (but wondering if having only 1 solar panel, so that there is nothing above / too close to the antenna, would be a good idea to keep good signal). If 1 is enough (in particular in tropical regions such as Tahiti), this would be very little added complexity to the manufacturing process :) . There may be a tiny bit of work the first time finding the best way to make holes in the box for the cables, + glue with epoxy the solar panel on the top of the OMB, + make all of it waterproof with silicon, but nothing bad I would think
• a battery would need to be used as a buffer for peak power use and at night, this is also supported; maybe something like https://www.sparkfun.com/products/13856?_ga=2.10737524.1511975063.1685442033-1650352225.1596177951 or similar (since the SF batteries do not ship internationally) would be good. A bit of capacity would be good (so the system can last for a week or two without sun), in case of storm / bad weather etc.
• maybe some ballast would be needed at the bottom of the OMB to make sure it stands "up" despite the added weight of the solar panel at the top, and the less weight of the (now absent) large primary batteries at the bottom
• the main pain will likely be getting used to sourcing the components + finding the right connectors and using the right polarity, but this should be "easy" to sort out at prototyping. I think all of this is JST connectors, both for battery and solar panel. It is a bit hard to find from the AGT which JST is used, but looking at comparible battery, e.g. https://www.sparkfun.com/products/13856?_ga=2.10737524.1511975063.1685442033-1650352225.1596177951 , it looks like what is needed is JST-PHR-2Pin .

I will look at sourcing and add to the shopping list :) .

[jerabaul29]

An extra note: it makes little sense to monitor the voltage of the LSH20 as it is completely flat, but monitoring the voltage of the LiPo battery would make sense :) . I can add it to keep it in the back of my head (to add a "battery monitoring information", for example to the GPS fix information or the wave messages).

[gauteh]

https://github.com/gauteh/sfy/issues/136