Powering Itsy Bitsy, FONA and sensors all with the 1.5A LiPo

[summitsurf]

I have an idea for a remote sensor package connected with a FONA and controlled with an ItsyBitsy 32u4 (3V). Can I power it all with a solar panel/battery/1.5A charger? I included my breadboard idea. Only thing missing is the solar panel obviously attached to the charger with the barrel connector.

[fgnievinski]

Hi. I have similar needs, I hope you don't mind offering some specific questions.

I understand the FONA must have a battery because of the 2A spikes. Can we have a single battery, plugged in the solar charger and shared between FONA and the main board (Itsy Bitsy here, M0 Adalogger in my case)? Or do we need a secondary battery connected directly to the FONA -- and if so, can it go lower than 1200mAh?

Would the internal regulator in FONA be okay with the solar chager's output voltage range? It can be "as high as 6VDC if in direct sun because it will draw current directly from the 6V panel instead of from the battery." The LOAD output can also be as low as 3.1V when running on batteries (overnight).

Can the solar charger's LOAD output be shared in parallel between FONA and the main board? Or should we route power through the main board (Adalloger or Itsy Bitsy) to the FONA? Or vice versa: connect the solar charge to the FONA then connect FONA's 3.3V regulator output to the main board's BAT pin?

I also note the FONA tutorial discouraged to "Connect an external 5V power supply to the USB and GND pins", recommending to "wire it to a USB cable's 5V and GND input". So, I'm not sure how to feed FONA's built-in charger.

Sorry for so many questions.

-Felipe.

PPS: @summitsurf could you share your diagram files? was it made in Fritzing?

PPS: here's a photo of my current setup: Adalogger and GPS feather with solar charger + 6W panel + 4400mAh battery:


It's been running 24/7 outdoors, here's the battery voltage over a year:


Now I'd like to include the FONA, hence the questions.

[summitsurf]

I just went ahead and ordered the parts. @fgnievinski I'll keep you posted as to some testing I plan to do. What other diagrams do you want? I am new to fritzing as the breadboard drawing above was my first attempt.

[fgnievinski]

good luck, @summitsurf, please do keep me posted!

here's my build tutorial, if that's of any help.
see especially the appendix, describing the design of the energy supply system.

I'm also new to fritzing, if it's easy for you, could you post your sketch (.fzz file)?

thanks
-Felipe.

[summitsurf]

Ah ya here is a link
https://www.dropbox.com/s/mprnnf4wg65a1 ... r.fzz?dl=0

I had to add all the fritzing parts to my library not sure if they are saved in the fzz file or not. I'll check out your build tutorial thanks!

[fgnievinski]

I was able to open the sketch in Fritzing -- super cool, thanks!

here's the shopping list generated automatically:

Amount Part Type Properties
1 Battery Holders package lipo-1100mAh; variant 1100mAh
1 Adafruit AHT20 Temperature and Humidity Sensor variant variant 1; part # Adafruit #4566
1 Adafruit FONA - Mini Cellular GSM Breakout variant SMA
1 Itsy Bitsy 32u4 3V @ 8MHz variant 3V 8 MHz; part # Adafruit 3675
1 Adafruit BQ24074 Solar-DC-USB Lipo Charger variant variant 1
2 2.2Ω Resistor package THT; tolerance ±5%; bands 4; power 0.25; resistance 2.2Ω; pin spacing 400 mil
1 Maxbotix MaxSonar Ultrasonic Sensor

[fgnievinski]

I've purchased the Adafruit FONA yesterday:
https://www.adafruit.com/product/1963

Let's see how to mix and match with the parts that I already have:
https://www.adafruit.com/wishlists/469752

[summitsurf]

Cool! Didn't know about that shopping list feature. I did order a larger battery, 2200 mah? and a solar panel. I couldn't see your wishlist for some reason. Showed an empty cart. My parts should be here early next week!

[summitsurf]

Got all the parts but I cannot connect to the mqtt broker in adafruit IO. I should clarify that I have yet to try it all with the solar panel and battery. This is just with the USB connection so far. I'm off to seek help in the adafruit io forum now.

[fgnievinski]

great, good luck with the IO.

my FONA should arrive by Thursday.

I've sketched some power supply scenarios:

option 1:

opt1_bb.png (224.95 KiB) Viewed 567 times

option 2:

opt2_bb.png (252.1 KiB) Viewed 567 times

option 3:

opt3_bb.png (254.05 KiB) Viewed 567 times

relevant excerpts:

"VBAT & GND - these are the same pins as the 2-pin JST connector. Connect to a 3.7V/4.2V Lipoly/LiIon battery. Do not power from a power supply or LDO. Use only a battery, at least 500mA, 1000mAh+ is best since there can be 2A spikes of current"

https://learn.adafruit.com/adafruit-fon ... -2046028-8

"5V (left middle) - this is the USB 5V from the microUSB connector when its in and powered. Good if you need to know when the microUSB is plugged in and/or want to recharge the battery from an external plug."
https://learn.adafruit.com/adafruit-fon ... 2046030-10

[fgnievinski]

I've read some more:

The problem with the load-sharing is that you can feed to full 6V from the panel into the FONA. The FONA is expecting battery voltage levels, and you risk burning it out. If you wire to the battery output, you will only get battery levels.

and:

You would not want to much connected directly to the battery as charging and drawing power to and from the battery at the same time is not a good idea.
The fona however can only deal with the typical lipo voltage range and it draws very short term up to 2 amps - not good to route this through the load part of the charger and/or other circuit.

So, I think this fourth diagram would be best.

opt4_bb.png (229.29 KiB) Viewed 556 times

[fgnievinski]

I just realized you're using the newer v3 solar charger. Its LOAD output voltage is regulated to never be over 4.4V (instead of 6V as in the older model). On the other hand, the LOAD pins output current is 1.5A max (instead of 1.8A in the older model). In either case, I think it's still better to connect the FONA in the battery pins instead of the LOAD port.

Here's a fifth diagram, it's equivalent to the fourth diagram, except I'm using the older v2 solar charger:

opt5_bb.png (230.6 KiB) Viewed 552 times

[summitsurf]

So I have almost the same setup now. I'm just using the JST to connect to the FONA and the OUT to connect to the PowerBoost 500(and on to the 5V Itsy) because the 4.4V was not enough. I am using the newer version of the solar charger. Now everything works fine when I am hooked up to USB and running. Publishes to the IO feeds and all. When I try to just use the battery the red LED on the FONA blinks every 3 seconds and not every 300ms consistent with GPRS connection. So something is wrong. Any clue on how to debug now?

[fgnievinski]

Everything I read about the FONA recommends connecting it directly to battery; in the case of the solar charger v3, that would be the lipo+gnd holes on the side.

[summitsurf]

Isnt that Lipo pin(on the solar charger) the same as Battery input? supposed to be connected to the positive terminal of the battery?