Photon white led w/ solar panel

The powerboost 1000 isn’t meant to output over 5.2V - so it looks like that isn’t working correctly. The problem with using an Voltage Regulator is the dropout level - you maybe able to find one that outputs 5V and has a drop out of 0.2V or use a zener diode?

:radioactive:CAUTION Crotchety old engineer post ahead…:radioactive:

It’s a little unclear how everything is connected together, but it seems like you have an excess voltage that doesn’t have anywhere to go. You could add a voltage-activated bleed resistor which would be easy enough to implement, but it’s just another thing to hang off of this chain-hack.

6.16V is still less than 6.5V, so I’m not sure how you’ve determined that is definitely the problem.

It seems an awful lot like you started with an idea of what is wrong in mind, and you’re looking for evidence of that. It may end up leading you somewhere, but it will waste your time if you ignore evidence to the contrary.

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The issue is that the power boost is just that, a voltage booster not a buck device - so it will take anything lower that 5.2v and make its so - it will NOT reduce excess voltage on it’s input.

The culprit here is that solar charger as it (like many in the same category) does not shed excess voltage generated by the solar cell, its job is to get max power (V*I) from the cell and so it will pass through any voltage it receives on the load output after diverting some power to charge the cell if needed - so once the cell is full the voltage will rise as the sun delivers more energy - which is what is happening with the observed issue by the OP.

This is why you always need a buck/boost convertor to stabilise the desired load voltage after some (unregulated) solar mppt’s.

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That is not very clear from the Adafruit specification - it seems to suggest that adding a USB type A socket and using that output will provide a USB spec 5V! I guess the conclusion here is go back to the drawing board with this circuit and ensure that that the solar panel output is limited to 5V first then use that to charge the LiPo and power the Photon.

Sort of :slight_smile:

The Adafruit is going just whats promised i.e. boost a battery level to 5.2V - what it omits is that if the input is higher - its passed through :slight_smile:

The best way is to use the MPPT to extract max power from panels:

The open circuit voltage of a panel can be quite high and the MPPT endeavours to take the max power from the feed to charge the battery while providing at least the battery voltage to the mppt output. Once the battery is chargde then the output floats upto the max voltage from the panel (based on output load only now - in the case of a particle, not much, so it will probably float to panel max) - Now when the sunlight drops this will taper off until just the battery voltage is presented (until its flat) etc.

So what you should now do is have a buck/boost regulator (or inverter in AC based systems) that will handle the max and min input levels and produce your stabilised output needed.

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Thanks for all the excellent input. I have some of the Adafruit buck/boost converters on the way and I’ll post again how things go.

When putting this together I assumed that it would limit the voltage of the output. A good lesson and time well spent.


Great explanations @shanevanj

Another possible solution is simply using a 5V Panel and an Argon.
If @davidcool cant source a 5V panel that’s large enough to meet the Power Requirements, this may be a good project for Mesh with a Solar Powered Xenon that reports the sensor readings to a nearby Argon on mains power.
Either version is cheaper and cleaner than the current setup.


My goal with this system is to get a really robust unit that can run year round 24/7 and withstand even several days with little to no sun. After I get a stable system I plan on using a lot of Borons so these can be placed in streams, and forests, etc. I’m gearing up to work with schools in China, Bhutan (up in the Himalayas), Thailand as well as here in the US. A college in upstate New York will also use them in a forestry program.

This is also designed to be used in classes ranging K-12 to college, and other DIY types. I wanted to stick with more “off the shelf” type components so anyone, anywhere could easily implement this. That’s also why I used female header pins so it’s easy to connect and reconfigure components on the fly, a must with students putting these together in mind and also reusing or replacing components.

I’ve been playing with Xenons and Argons for the last week. I love the cost reduction but it comes at a cost of a bit more complexity in setting up. Fine fore me but maybe a bit daunting for first timers or students just learning.

If anyone has test cases or design profiles for different particle devices running on solar, please share links. I’d love to see some more detailed technical specs, wiring diagrams, sourcing, etc. on more “refined” or simplified systems that are tested and stable!

Thanks again to everyone for all of the valuable input and keeping me moving…


@davidcool, Boron’s will change everything (for the better).
With a Boron, you can remove all the extra gadgets, and use your 9W panel directly.
In reality, a smaller panel could work with a sleeping Boron.

Have you looked at this project


Hi all,

I got that Adafruit buck/boost verter in the mail today and swapped out the power boosts on two units… Both ran perfectly all day. @shanevanj that power boost was indeed drifting to higher voltages once the battery was full…

I have the Boron up and running now. I’m going to try and run this same setup, just minus the Sparkfun fuel gauge b/c it’s built into the Boron. I plan to run the buck / boost directly into the VUSB, that goes through the power regulator down to 3.3v correct?

I just had a moment to look at that solar based PCB project for the Boron, but it looks great. I’d love ideas on the most efficient / cost effective ways to configure the Boron to run 24/7 taking readings every 2 min or less on nothing but solar.

Thanks again for all the input to help resolve this, most appreciated!

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The Boron is much more forgiving in terms of Input Voltage.
As said previously, you can use your (6V) 9W panel directly with a Boron or Electron (but Not Photon, Xenon, Argon).
Or something cheaper like a standard 12V panel, along with a 12V SLA Battery if space isn’t a concern.
Another benefit to having a 12V battery with much more capacity than you need, is that it allows you to easily add a timer relay to minimize the chance that you will need to travel to the site to Reset the Boron in the future.