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Feather 32u4 FONA and USB / DC / Solar Lithium Ion/Polymer c
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Feather 32u4 FONA and USB / DC / Solar Lithium Ion/Polymer c

by GRAY8 on Thu Apr 06, 2017 8:41 am

I have a water level sensor that posts distance data to a cloud platform. The sensor uses the USB / DC / Solar Lithium Ion/Polymer charger - v2 to charge a Feather 32u4 FONA via a solar panel. When not in direct sunlight, the Feather 32u4 FONA functions properly. When placed in direct sunlight, the FONA does not function. Removing the sensor from direct sunlight re-activates the Feather 32u4 FONA.

While in direct sunlight the chargers red and yellow LED's are solidly lit.

Thank in advance for your help,

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Re: Feather 32u4 FONA and USB / DC / Solar Lithium Ion/Polym

by adafruit_support_mike on Fri Apr 07, 2017 4:03 am

Post a photo showing your hardware and connections, plus a link to any documentation for the sensor please. 800x600 images usually work best.

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Re: Feather 32u4 FONA and USB / DC / Solar Lithium Ion/Polym

by GRAY8 on Fri Apr 07, 2017 10:15 am

The following is the link to the ultra sonic senor: https://www.adafruit.com/products/1137
Below are internal and extrenal images of the sensor node.


Thanks,

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Re: Feather 32u4 FONA and USB / DC / Solar Lithium Ion/Polym

by adafruit_support_mike on Sun Apr 09, 2017 4:36 am

When you say 'sensor':

Removing the sensor from direct sunlight re-activates the Feather 32u4 FONA


are you referring to the MB7092 or the entire assembly (specifically including the solar panel)?

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Re: Feather 32u4 FONA and USB / DC / Solar Lithium Ion/Polym

by GRAY8 on Sun Apr 09, 2017 8:12 am

I'm referring to the entire assembly, to include the MB7092, a Adafruit Feather 32u4 FONA, a USB / DC / Solar Lithium Ion/Polymer charger - v2, a Lithium Ion Battery Pack - 3.7V 6600mAh and a Large 6V 3.5W Solar panel - 3.5 Watt

When the red LED on the charger is not lit, the Feather functions perfectly. When I place the unit is sunlight, and the red and yellow LEDs light on the charger, the Feather ceases to function. The NET LED (Blue) on the Feather ceases to blink.

I'm using this unit to monitor flood conditions, any help you can provide is greatly appreciated.

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Re: Feather 32u4 FONA and USB / DC / Solar Lithium Ion/Polym

by adafruit_support_mike on Tue Apr 11, 2017 5:09 am

Thank you.

It sounds like you're getting overvoltage through the Solar LiPo charger.

The MCP73871 that handles LiPo charging passes input power directly to the output as long as an external supply is connected. A 6v solar panel in direct sun can generate enough voltage for the LOAD output to exceed 5v. The FONA is probably shutting down to protect itself when that happens.

The solution is to change the connections slightly. Instead of connecting the FONA to the Solar Charger's LOAD jack, move the connection over to the secondary holes for BAT. That will connect the LiPo directly to the FONA, and the voltage reaching the FONA will never exceed the normal working range for a LiPo.

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Re: Feather 32u4 FONA and USB / DC / Solar Lithium Ion/Polym

by colemanjj on Fri May 25, 2018 12:02 am

Glad to hear that one can go from the secondary holes for BAT to the Feather FONA.
To avoid the direct feed from the solar panel to the Feather FONA that could overload the Feather, I took a different approach: I ran a wire from Load Output to a USB male that I plugged into the USB female on the Feather FONA.
My logic was that the USB input on the Feather FONA probably would have some voltage regulation to bring the input voltage down so it would handle high voltages from the solar panel better that if I ran the charger directly into the Feather FONA's battery jack.
I thought this approach would take advantage of the direct feed from the solar panel when the battery was full but maybe not blow up my Feather FONA. It also means I can have 2 batteries in the system, one on the solar charger and one plugged into the Feather FONA.
It's working, but so far I've only used a smallish solar panel that maxes out at about 6.5 volts. Any sense to my logic or will I eventually blow up my Feather FONA with this setup?
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Re: Feather 32u4 FONA and USB / DC / Solar Lithium Ion/Polym

by adafruit_support_mike on Sat May 26, 2018 3:54 am

Your basic assumption is incorrect: the Feather relies on the USB cable to regulate its own 5V line. Nothing on the board limits the USB connection to 5V.

PCB space is a precious commodity on the Feather, and there isn't room for parts to double-check something that has to be within 150mV of 5V to remain compliant with the USB spec.

It sounds like you're seeing the same overvoltage problems, and the solutions will be the same as the ones discussed above. The Feather doesn't have a lot of room for flexibility when it comes to power connections.

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Re: Feather 32u4 FONA and USB / DC / Solar Lithium Ion/Polym

by colemanjj on Sun May 27, 2018 10:57 pm

mike,
thanks for the reply. I don't feel like I'm having overvoltage problems, at least not with the small solar panel I've been using, I'm just unsure if my solution of running power in by way of the usb port made any sense. I think you're saying it doesn't.
I know if I use a 6V solar panel it can output in the 7-8V range in direct sun, so I thought I might be protecting myself by running the input to the Feather from the solar charger through the Feather's usb port.
Am I correct in understanding your post as saying that running it through the usb doesn't provide any protection against overvoltage from the solar panel? Therefore the only solution for powering the Feather from the solar charger is by feeding the Feather from the secondary battery hole?
Sorry I'm being pedantic about this, just want to be sure of the options to solar power a Feather, its a great unit.
thanks,
john

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Re: Feather 32u4 FONA and USB / DC / Solar Lithium Ion/Polym

by adafruit_support_mike on Tue May 29, 2018 3:18 am

colemanjj wrote:I don't feel like I'm having overvoltage problems,

The first rule of debugging is to distrust anything you haven't verified with a measurement. 99 times out of 100, the point of failure is something that isn't doing what we assume it should be doing.

The second rule of debugging is to distrust any measurement you haven't confirmed by some other means. Assuming the instruments are working as expected is one more idea that can be wrong.

colemanjj wrote:Am I correct in understanding your post as saying that running it through the usb doesn't provide any protection against overvoltage from the solar panel?

That's correct.

colemanjj wrote:Therefore the only solution for powering the Feather from the solar charger is by feeding the Feather from the secondary battery hole?

Connecting a 6V solar panel to a Feather's BAT pin will kill the onboard LiPo charger through its output port.

Connecting the panel to the Feather's USB pin is functionally identical to sending the power in through the USB jack. The USB pin is directly connected to the USB jack.

Connecting more than 6.5V to the Feather's USB pin or jack will kill the LiPo charger from the input side instead of from the output side.

If you want to guarantee the voltage going into the Feather will be no higher than 5V, you have to add an external voltage regulator.

Taking a step back from the mechanics of connecting power to the Feather, trying to charge a LiPo directly from a solar panel doesn't work very well. The charger wants a reliable and well-regulated power source, and solar panels are notoriously variable. To use a solar panel efficiently, you need a circuit called a Maximum Power-Point Tracker (MPPT) which self-adjusts to the voltage and current levels that use the energy from the panel best.

We have a simplified version of that in the shop:

https://www.adafruit.com/product/390

and the Design Notes page from the tutorial explains the issues involved in making it work:

https://learn.adafruit.com/usb-dc-and-s ... sign-notes

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Please be positive and constructive with your questions and comments.