Solar Powered Spark Core

For myself I’m wondering what kind of solar trickle charger / solar battery setup would be best for long-term outdoor installations, I wonder if anyone has started thinking about these?


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Dave, look at timb’s battery shield work! :smile:

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That’s a good idea! I’ve never had an excuse to put a solar panel on a project. I will look into that. I have no idea what size panel is needed to power the spark core’s 150mA.

I moved this to a new topic so it will be easier to find :smile:


There are several commercial products out there for example Solar’s but I like the look of this minimalist trickle charger which is about 10% of the price. By sizing the solar panel to limit the charge rate to C/20 for NiMH the charge circuitry is reduced to a couple of diodes.
I intend to try this when Spark deliveries restart. (Unless wiser heads explain that it is a bad idea.)

It’s somehow related to the topic but not directly:

  1. The :spark: core for this matter should be consuming lower power. 300mA * 5V = 1.5W is kinda power hungry in an outdoor solar project. Well, unless don’t have space constraint and a medium size solar panel is ok.

  2. There should be 2 battery imo. The Solar battery and something like a supercap for the :spark: core.

  3. The A123 or LiFEPo4 might be a good solar battery candidate and a MPPT charger feeds to the battery-charging circuit :smiley:

I always had this wild idea of having a controlled battery bank. Maybe we have 5 x Solar battery in parallel and the weather condition today only allows for 1 battery to be charged up or there’s too much load for the Solar. So we switch out one battery for charging and leave the rest to power the system.

Doing so gives more flexibility and control over the livability of the project outdoor. :smiley:

But that’s just my crazy idea and the electronic switch hasn’t been that easy to be implemented. If you do have a clue or maybe i’m not talking sense please feel free to comment!

There are lots and lots of commercial products of course–this one is nice in that you can use solar or USB to charge:

I also have some Goal Zero gear for camping that works great with the core. I don’t know if folks should pay for the rugged camping enclosures if they are mounting their project inside another enclosure. You are also going from Vbat to USB and then USB to 3.3V for the core with adds a bit of power loss.

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I bought a 1w 6v solar panel today and tried unsuccessfully to power the core. 1w is barely enough to for the steady state current. Not sure that should be enough to power the core with out a battery. Also, I was using a 5v regulator so the differential of input to output voltage is probably not enough for the regulator.

Next I am thinking about trying a 4.5 v panel down stream of the regulator diode fed with the reg output. I can also try a panel with a 1.5 w output also. But I don’t know if it is ok to power the core from the panel without a regulator.

Any thoughts

So i mentioned above it’s like 1.5W average…

You can plug the solar panel directly to the Vin pin without a regulator. Vin goes to a regulator and output 3.3v to power the core.

A step down would be best… Like 6V to 3.3V and directly to the core. Be careful though! if you didn’t do it correctly, the core will blow. That’s why there’s a regulator for steady supply and protection :smiley:

Oh thanks, sorry I didn’t read through all the post yet. I was thinking out loud.

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I see now that the power input is 3.6 to 6v. I wonder if I would be better off with the 4.5v 1.5w panel so that im right in the middle? With no load i saw up to 7 v with my 1w 6v panel. Do I need a battery in parallel to buffer the voltage or could I just run the panel straight in by itself?

If you’re going for the Vin, there’s no issue. Maybe a huge capacitor would help to minimise the fluctuation :slight_smile:

This MPPT solar charger breakout was announced over at Sparkfun today:

That Linear Technology part is nice and about $5 at Digikey if you want to roll your own.

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I think I’m going to have to jump on the solar bandwagon very soon. I just ran an extension cord out the dog door and into a “cold frame” in my yard…

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Ok, I’m getting there! I tested a 4.5v 1.5w solar panel with a 3.6v nimh battery pack and have success. The core still would not start up on the panel alone due to initial current draw. Once running I can remove the battery and it will continue to operate but occasionally crashes due to higher current draw. In my application I will replace the battery with a regulated power source from my jeeps battery. I think I could have used a smaller solar panel since I am only using it to offset the average current draw and have the jeep for momentary high demand. My next problem was the darn 7805 which is not efficient and running hot due to the large voltage drop across it. I wanted a switching power supply to eliminate the heat and reduce the current draw on the jeep. While looking for a cheap easy solution, that might be hiding in my house, I turned to a little USB port for cigarette lighter sockets and found the perfect jewel inside. I added a resistor in parallel with one on the board to change the adjustable output to 3.6v so it would be below the voltage of the solar panel when the sun is out. Now the core is only drawing 70ish ma from the 14v source. Success! Next I need to test the current draw of the solar panel at night to see if a blocking diode is needed (solar panels become loads at night and drain the battery). I’m hoping this panel is so small it will not be a problem. But if I do need it I will use a germanium diode to minimize the voltage drop. I want to keep it as high above the regulator setpoint as possible so the panel will take over most of the day. I will try sticking the panel to the inside of my windshield with some small pieces of clear double sided sticky tape. I think it is all going to work great!

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That looks good @pitchlynn. I have followed a similar route. I have implemented the very simple trickle charger I mentioned in my earlier post. I still don’t have my new Sparks so I am running with a Ciseco RFu-328 (An Arduino with a built in 898MHz tranceiver) which I ordered on April 13 and was delivered on 15 April. Great delivery - but I wish Ciseco had the very strong community support that Spark has.

The solar power comes from a pair of 5.5v 90mA solar panels connected in parallel (£3.49 each from Hobby Components). These keep 3 AA NiMH batteries topped up but can’t overcharge them. (you could probably up the charge current to 400mA safely with 2000mAh cells). The panels came with diodes and I’m pretty sure they are needed to prevent discharge at night.

The panel/battery combination delivers between 3.4 and 4.7 volts which I put through a TC1015 regulator (3.4 - 6v in - 3.3v out costing £1.45 on a breakout board). I sleep the radio and 328 about 90% of the time which gets the average current draw down to under 5mA and comfortably balances power use in the cloudy UK.

I’ll move it over to the Spark when it comes. I appreciate I’ll either have to up the panel size or sleep a bit more to keep the power balanced.

One issue is with over the air programming. With the RFu-328 I have included an LED that lets me know when the radio is awake but I can see myself peering through binoculars to see when to hit the upload button.

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If you do all of your programming after dark, you’ll be able to see the :spark:'s cyan LED from miles kilometers away. No question as to when that thing is on or not!


If anyone is interested, Brown Dog Gadgets has a 20% off everything promotion going on until May 31st, 2014. The promo code is “instructablescontest2014”. I think I’ll be ordering some solar gear soon!

Sorry to revive an old thing, I’ve tried several ways with a photon with a 1W solar panel and some 2000mAh Lipo, with Sparkfun lipo rider pro and other solutions, and I never have it working correctly after one week.

On the other side I have couple of arduino working perfectly with the same configuration.

Has some experiment been successful ?

[quote=“epierre, post:19, topic:3812”]
I’ve tried several ways with a photon with a 1W solar panel and some 2000mAh Lipo, with Sparkfun lipo rider pro and other solutions
[/quote]Can you describe your setup in a bit more detail? Does your arduino use WiFi? Are you deep sleeping the Photon, and if so, at what intervals, etc? Adding more details would better help us help you. :grinning: