Category Archives: Solar Stage

Then there was three…

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Remember the new PV modules I barely mentioned previously? Well, it turns out that two was much better than one. Now we shall see how three in parallel will compare. This time I’ve stuck to nonpermanent adhesive (ha ha) so it can easily be remodeled. Lesson learned from a previous module multiplexing experiment.

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Testing under way, full sun ahead!

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Board with test terminals in constant current phase of CC/CV charge.

After building a Solar Stage with integrated terminals on the PV and battery for connecting an ammeter, I am now collecting data relating to the solar boost output and constant current/constant voltage charge cycle.
Data will be posted once recorded and graphed.
So far, the more sensitive PV modules connected in parallel provide charging current before noon from inside a north west facing window.

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Testing rig

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To allow for current measurement, a Solar Stage has been assembled with clips on both power interfaces (PV module and battery) for connecting an ammeter in series.
Of course, the sun disappears shortly after it’s ready to go. More to follow.

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On a breadboard somewhere on Planet Earth…

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So after having some trouble with the Solar Stage’s LT4071, I took Greg’s advice and recreated the LiPo charge circuit on a breadboard. I used a proto adapter boards leftover from my attempt at breadboarding the SPV1040 solar boost (see why breadboarding high freq circuits is trouble).
After following the instructions for the charger IC’s eval board, it powered up and switched to supplying the battery through VCC after the power was removed. This was verified by watching impedance of the HBO pin, which went to 0 Ohm when it hit the charge cycle.

Moral of the story: examining sub-circuits is useful and rewarding!

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Poly PV cells arrived

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Polycrystalline photovoltaic cells (1V @ 500mA, 60*60mm) arrived today from a responsive eBay seller. At $2.50 each, they were the cheapest I could find within the spec for the Solar Stage. Took 3 weeks to arrive (Singapore Post). Preliminary tests show they perform well.

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At the dirty board house in Shenzhen

Through the marvels of globalization and modern technology, my solar charger design, dubbed the Solar Stage, has been sent off to a board house in China for low cost production. Thanks to DirtyPCBs, and its sassy yet functional website, I placed my order for 9 to 12 boards of my 10 * 10 cm 2-layer design for only $25 (including Hong Kong Post — no tracking). Yes, that’s no typo. $25. Oh, and a pick from 6 colours (I chose red). 5 * 5 cm is a jaw-dropping $14.

Front of the image generated by the DirtyPCBs website. After countless revisions, the board is ready. A Dangerous Prototypes Bus Pirate and a self-designed SD/flash combo board occupy the space unused by the Solar Stage.

According to the DirtyPCBs website, my Gerber files are transmitted through their automated system to a board house in the high tech heart of China, where it’s batched up with other boards and given the full treatment. The boards are then forwarded on to the DirtyPCBs agent, to be sent on to me. The whole process takes 6 to 8 days, not including the postage time (1 to 8 weeks for Hong Kong Post, dependent on your country). Amazing!

Back of my board order.

One feature I really appreciated is DirtyPCBs unlimited file revisions. Up until the point the board design is sent to the board house, the site accepts a re-upload of your design files. In the 31 hours before it was batched, I submitted five (5) updates. In my post-submission high, I noticed little bits I could improve and went over everything with a fine-tooth comb. Nothing like the thrill of working against the clock! Granted, it might be a bust, but at least I have some useful boards out of the experience.

To be honest, I enjoyed the cheeky language that peppers the website. Apparently the website was originally made as a joke poking fun at people complaining about the quality of a new process. Or a very clever dirty marketing. Either way, the results are impressive for the cost, so I decided to give them a shot. Tonight I received a notification saying my board has been batched up. Stay tuned for an update when my dirty boards arrive.

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Filed under Battery power, DIY, fabrication, ICs, micro-controllers, PCB design, Solar Stage, Teensy

Progress on solar MPPT board

My first stab at PCB routing, using the design rules from DirtyPCBs.com.

Perhaps overly complicated, but the challenge of routing a bunch of pins so close together was pretty fun. I will post a final schematic later, but here is what I have so far. Don’t mind the cramped nature of the drawing, for I am contending with EAGLE’s freeware limitations & paneling to cram other useful stuff onto the remaining 10*10cm DirtyPCBs.com allows.

Top layer

Bottom layer

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Filed under Battery power, DIY, fabrication, ICs, PCB design, regulators, Solar Stage, Soldering, Teensy