Using arduino uno, solar panel & rechargable batts
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Using arduino uno, solar panel & rechargable batts

by kelly7552 on Wed Jun 29, 2011 2:37 am

Is there a way to power an Uno (or uno on a breadboard), a xbee, a BMP085, an HH10 humidity sensor, a thermisistor, a photocell, etc. etc. from a solar panel that charges a rechargeable battery and then the battery provides constant power?

I've seen lots of setups where the adafruit solar panel provides power with a battery connected with a diode, but it looks like the battery would draw down when the solar isn't working.

I was looking to use 2 adafruit 6V solar panels, and maybe 2 3.7 volt lithium ion batteries. All that sounds great, but what would the circuit look like to provide 5V (and 3.3V) power to my breadboard?

Again, the solar cells should provide 12V in parallel which should be enough to recharge the batteries for 24+ hours which should be able to run the arduino with sensors and an xbee.

I'm a software geek and I;m afraid I'll probably find a way to bring this project to a shocking conclusion. :D
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Re: Using arduino uno, solar panel & rechargable batts

by adafruit_support_bill on Wed Jun 29, 2011 5:59 am

Have you looked at the Solar MintyBoost project?http://www.adafruit.com/blog/2010/07/09/how-to-make-a-solar-mintyboost-a-solar-power-charger-for-your-gadgets/
This uses a solar panel to charge a single lithium cell. The MintyBoost then boosts the 3.7v to 5v.
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Re: Using arduino uno, solar panel & rechargable batts

by kelly7552 on Wed Jun 29, 2011 11:59 am

AWESOME! The instructions use a 1200 Mah battery, you sell a variety of larger batteries, is there an advantage for using a larger battery with this setup?

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Re: Using arduino uno, solar panel & rechargable batts

by kelly7552 on Wed Jun 29, 2011 12:04 pm

Oops, forgot to say that I have the 2W solar panel!

-Bill
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Re: Using arduino uno, solar panel & rechargable batts

by adafruit_support_bill on Wed Jun 29, 2011 12:27 pm

You can use a larger battery. The charge-rate on the controller is configurable with a resistor so you can reduce the charge times for larger capacity cells.
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Re: Using arduino uno, solar panel & rechargable batts

by exxpi on Wed Jan 04, 2012 2:08 am

I'd like to jump into this post, rather than starting a new thread, as the OP seems to have had his question answered. I read through the battery FAQ and understood about half of it, so I still have some questions.

I have the following equipment:
  • Arduino Uno
  • Xbee v1
  • IR Emitter & Detector
  • LinkSprite JPEG TTL Camera
  • 6v 2w solar panel
  • 3.7v / 850mAh LiPoly
  • Adafruit LiPoly Solar kit

I bought the battery a while back thinking it would be strong enough to power the whole setup on its own. It appears I was quite wrong. But I'm confused as to why. I've read the battery FAQ but only understood parts of it. If the Arduino Uno accepts voltages from 6-20v, is it because my battery is 3.7v that it can't power it, or because it can't push enough current? On the same note, why is the solar panel unable to power it if it's 6v?

My goal is to have the battery power the whole setup while the solar panel charges/supplements it during the day, so that the battery can power it throughout the night, rinse and repeat the next day. Is the 6v/2w panel not strong enough to get it the juice it needs, and is my battery too weak? I've already ordered a new 3.7v, 2700mAh LiPoly to see if there's a difference, but I'd like to know the theory/logic behind it.

It's set up correctly. The solar panel is plugged in, and the PWR GOOD/CHRG LEDs are blinking (not lit very well right now). The battery is plugged into it, and the LOAD is connected via a soldered 2 wire JST-to-2.1mm converter, and plugged in to my Uno's DC jack. My XBee's green power LED (I'm using the Adafruit XBee Adapter also) is blinking steadily as if it's got enough power, however my Uno's LED on pin 13 has not shut off as it normally does after resetting. As if maybe it is stalled while booting up. My IR emitter LED appears to have a correct voltage drop, however it looks like the total voltage coming out of 5V is closer to 3V or so, which seems to tell me that it's just not getting enough power :(

Is this a realistic goal? Will a larger capacity battery make the difference? Should the 6v/2w panel provide enough output to power the setup on its own, or should I rely on the panel strictly to keep the battery topped off?

Thanks so much for any help or direction you can provide, even if it's just links to other guides. I'm happy to learn the stuff, it just seems like I'm going in circles and spending money on dead ends.

[Edit]: Oh and just to add: Will using two of the 6v/2w panels make a difference, provided that they can get the same amount of sun exposure?
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Re: Using arduino uno, solar panel & rechargable batts

by adafruit_support_bill on Wed Jan 04, 2012 7:40 am

If the Arduino Uno accepts voltages from 6-20v, is it because my battery is 3.7v that it can't power it, or because it can't push enough current?

It is because the battery is only 3.7v. There are 3.3v Arduino variants. It is also possible to modify a standard Arduino to run on 3.3v: http://www.ladyada.net/library/arduino/3v3_arduino.html
Another possibility is to add a boost converter to boost the output up to the level that the Arduino needs: http://www.adafruit.com/blog/2010/07/09/how-to-make-a-solar-mintyboost-a-solar-power-charger-for-your-gadgets/
On the same note, why is the solar panel unable to power it if it's 6v?

That is 6v in full sunlight. A 'best-case' scenario. As soon as the sun drops behind a cloud, or low on the horizon, your Arduino will stop. (More likely, it will start to act really flaky for some time before it quits entirely). Adding the battery/charger to the circuit allows the battery to smooth the output and fill-in when the sun goes away.

I don't know what the power requirements of your TTL camera are, but the Solar Minty Boost configuration would be more than enough to handle the Arduino & XBee.
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Re: Using arduino uno, solar panel & rechargable batts

by Balloondoggle on Wed Jan 04, 2012 3:32 pm

I asked a very similar question a few weeks ago, and here is what I've settled on for an interactive public display involving audio. Keep in mind, I have NOT tested this setup yet!

12v 7Ah rechargeable battery
http://www.amazon.com/s/ref=nb_sb_noss? ... ry&x=0&y=0

Sony DCCE290 1000mA Car Charger
http://www.amazon.com/Sony-DCCE290-1000 ... B000095S9O

Instapark® 5W Mono-crystalline Solar Panel with 12V Solar Charge Controller
http://www.amazon.com/Instapark%C2%AE-M ... -1-catcorr

The Sony part is a car-charger with a 9v output. I thought it may be helpful to splice it in between the battery and the board to step down the voltage from 12v to 9v for the Arduino board, but since the board can handle up to 20v I may ditch this part.

My expectation is that the interactions will be low enough demand that the drain on a 7Ah battery will be minimal. With a well-placed solar charger keeping it topped off, I hope this will survive the May-October period of the display.
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Re: Using arduino uno, solar panel & rechargable batts

by bemental on Thu Feb 16, 2012 3:12 pm

You can use a larger battery. The charge-rate on the controller is configurable with a resistor so you can reduce the charge times for larger capacity cells.


I'm currently waiting on the solar Li-Po charger (http://www.adafruit.com/products/390) to be available again but was interested in your response to the previous question.

When you mentioned that the charge-rate on the controller is configurable with a resistor, is this a change to the stock charger resistor with a smaller resistor or something else entirely?


Thanks.
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Re: Using arduino uno, solar panel & rechargable batts

by adafruit on Thu Feb 16, 2012 4:45 pm

bemental wrote:
You can use a larger battery. The charge-rate on the controller is configurable with a resistor so you can reduce the charge times for larger capacity cells.


I'm currently waiting on the solar Li-Po charger (http://www.adafruit.com/products/390) to be available again but was interested in your response to the previous question.

When you mentioned that the charge-rate on the controller is configurable with a resistor, is this a change to the stock charger resistor with a smaller resistor or something else entirely?
Thanks.


please read the produect tutorial page linked from the product page for details on how to change the charge rate
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Re: Using arduino uno, solar panel & rechargable batts

by bemental on Thu Feb 16, 2012 8:40 pm

please read the produect tutorial page linked from the product page for details on how to change the charge rate


Found it, thanks - at the bottom of this page (http://ladyada.net/products/usbdcsolarlipo/use.html)
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Re: Using arduino uno, solar panel & rechargable batts

by bemental on Thu Feb 16, 2012 10:03 pm

First of all, thanks for the quick response!

Did some reading, have another question. During the parts selection process for the build I'm planning I created a spreadsheet with various panels, batteries, outputs, charging times, etc. Based on this new piece of information regarding resistors you provided I added some numbers to my spreadsheet and would love a bit of clarification.

Image

Adjusting the max current wasn't an issue previously because the panel I selected to use has a current < 500mA. I realize now that I can reduce the charging time via alternate source (i.e. 10w USB charger ala iPad 2) greatly, down from approximately 24 sunny hours, to 4 10w USB hours for the 6600mA battery, but this WILL NOT be my primary source of charging for the setup.

Now to the crux of my question: does a resistor reduce ALL current going through the system, or just those above the resistor's ohms? In example, if we modify the board and add the resistor will it reduce the current for all inputs (solar, USB, wall wort)?

My inclination is to say yes to the reduction of all current due to Ohm's Law, but I'm new to this and would appreciate any input!
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Re: Using arduino uno, solar panel & rechargable batts

by adafruit_support_bill on Fri Feb 17, 2012 6:56 am

The resistor sets the maximum charge rate for the battery - regardless of the input source.
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Re: Using arduino uno, solar panel & rechargable batts

by bemental on Fri Feb 17, 2012 9:39 am

The resistor sets the maximum charge rate for the battery - regardless of the input source.


So the analogy of a resistor as a "smaller pipe" adequate in that it doesn't effect lower currents?

In example, if we modify the board and add the resistor will it reduce the current for all inputs (solar, USB, wall wort)?


I'm new, and sometimes a bit daft... perhaps someone with a bit more time than the moderator could walk me through this one?
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Re: Using arduino uno, solar panel & rechargable batts

by adafruit_support_bill on Fri Feb 17, 2012 9:57 am

resistor as a "smaller pipe"

In this case, the resistor is not in the direct path of the charging current. It is a 'programming' resistor that tells the charge controller how much current should be allowed to flow. You might want to review the design details and schematics here: http://ladyada.net/products/usbdcsolarlipo/download.html
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