Solar Proto: What to do with the Parallax 2.5W solar cell (todays $7.49 DotD) ??

Tubular

Want to know what to do with the 2.5W solar cell (the $7.49 deal of the day)??

The LTC3108 from Linear technology harvests energy from sources as low as 20mV. It can be used with a single solar cell such as the parallax one on special today, and can even harvest energy from the fluoro's in your office to trickle charge up a supercap.

... you'll also need
* Parallax 2.5 Watt single cell (today!)
* LTC3108 from Linear technology (a few$)
* TSSOP16 breakout (eg Futurlec.com)
* Coilcraft 1:20 stepup transformer as per LTC3108 datasheet ($1.06)
* CAP-XX supercap
* Blank proto board
* MCP3208 (optional) for monitoring)
* The plywood packaging the Parallax cell comes in
* Drawer handle!

The LTC3108 charging power path is only about 4.5mA, but it can charge any size supercap, or 4.1 volt Li-ion/Lipo batteries. These can in turn provide much higher currents but at a lower duty cycle.

This was all inspired by Beau's mppt comp. Then I realized this really has very little in common with maximizing efficiency - in fact its terrible as far as efficiency goes!

cheers
tubular

Post Edited (Tubular) : 7/7/2010 11:44:07 PM GMT

WBA Consulting

Love it! I almost started a post this morning asking how I could make use of the single panel to power a small project. Results from doing google searches for solar panel chargers/power supplies makes your head spin. I have two 35W solar panels that output 8 volts and I am looking for a way to make good use of them.

ps. Excellent use of the $2.99 blank proto board also! I always think of stacking boards, but end to end looks great.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Andrew Williams
WBA Consulting
PowerTwig Dual Output Power Supply Module
My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger

Tubular

Thanks Andrew. It's a great option for powering low duty cycle electronics (sensors etc). It also works with Thermopiles (Peltier devices).
I wouldn't mind betting it could also work with a headphone output but that remains to be tested.

The proto blank is really great, and many thanks to Ken and mikediv making these available

Originally I had in mind a small module that would power the proto board via the 3 pin servo headers (a la ServoPal/SoundPal) ; but the 32mA quiescent current killed that idea for now.

Cluso99

Nice use for the Solar Panel Tubular

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)·
· Prop OS: SphinxOS·, PropDos , PropCmd··· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBlade Props: www.cluso.bluemagic.biz

john_s

Perhaps an off shot question but somehow related...

I wonder how/why did the manufacturers come up with particularly 4.1V for Li-ion/Lipo batteries (and not 3.6 or 4.8V for example) ?

Tubular

Hi John_s

Not quite sure if you're asking how the 4.1v arises (it's determined by the battery chemistry), or why the chips such as LTC3108 nominate 4.1v in their example circuits. I've also seen 4.0 and 4.2 volt setpoints used with other chips.

You can set the output voltage on the both LTC3108 and LTC3105 using a resistive divider, to any output voltage you like within the output range of the chip. There is also a second, AUX output which can be set independently with its own resistive divider. This allows a 3v3 rail for the Propeller, and 4.1v for the LiPo, for instance.

john_s

What I had in mind was the battery chemistry. I guess I found the answer here http://en.wikipedia.org/wiki/Lithium-ion_battery

According to that link when using different chemistry the LIB single cell voltage can be between 3.3 and 4.2V.