Students from Gansu Province pose with a Solar Lamp

 Shaanxi Province students assembling the Solar Lamp

Cost Reduction project begins

If there was one thing I was not totally satisfied with, was the material cost of the solar lamp. Being our first time through the process, we made a few cost decisions in order to keep the progress going and ship the lamps. With the first batch of 1000 completed, I'm looking at reducing the cost for next year's batch...phase 2 of the project.
The first item I am redesigning is the charge controller PCB...

 I am currently in process of designing this simple circuit on a single-sided PCB with the wire terminals in the same location as revision 1. I'm using the open source tool, KiCad for the first time. This board will be so simple I'll etch a prototype PCB myself.

The controller receives the solar panel power and regulates the charge going to the battery, cutting off charging when the battery is fully charged. The circuit uses an input from solar panel, and can charge a Nickel Metal Hydrate (NiMH) battery.

o        Cost reduction strategy: The solar panel is specified to have 0.5W maximum output power, so the power source is limited. My sample measurement was actually only 0.25W. For revision 1 PCB design, I overlooked the power source capability; and specified the use of a charge regulator IC, which would be needed in the case there is more power potential available than is needed (for example, AC wall socket source). Because the available panel power source to charge the batteries is low, it is not necessary to regulate the charging current.

o        The Solar panel power is 0.5W, at 5V the available current is 100mA maximum. The batteries can accept up to 125mA charge current.

o        Since the current is limited by the panel power, we only need to regulate the voltage. Using a general purpose diode, we prevent the battery voltage from exceeding the panel voltage. A very small value resistor in series can be used as a small power divider to insure the battery is not over powered.

o        Optional: using a zener diode, we clamp the battery voltage to a maximum of 4.7V. I doubt this zener diode will be needed in the end, but want to test it.

o        Optional: using a re-settable fuse (such as a Raychem polyfuse) in place of the series resistor can be used if we find a reason for more robust protection of overpowering the battery. I also doubt we will need a fuse, as the solar panel and series resistor limit the power.

First shipment made

Evergreen Education Foundation shipped first 400 solar lamp kits from the manufacturer to two schools, one in Gansu Province and another in Shaanxi Province. Additionally, schools will have an instruction video, Teachers Lesson Plan Guide, and spare parts to start their participatory science and technology learning program this semester.

Writing the Teacher's Guide

nA Teacher's Guide will be provided to the teachers of the Solar Lamp lessons. This document has the purpose of guiding the teachers making the actual lesson plans. I have created the guide with 4 suggested lessons with classroom exercises, science topic summaries, illustrations, and thought-provoking questions. nRubric was created to guide assessment standards. The overall objective is to foster creative thinking and ingenuity in the students.

1. I.Solar tea– basic (not mathematical) level study of light conversion to energy - by making sun tea.
2. II.Electricity and instrument usage teaches basic electricity, ohms law calculations, and practical usage of multi-meter and hand tools.
3. III.Fruit battery – basic level (not mathematical) study of chemical storage of energy -by making a battery out of a piece of fruit. 
4. IV.LED and semiconductors - Very basic (not mathematical) semiconductor theory and LED operation. n

nThe Teacher's Guide is being translated by my friend Melinda, a Chinese High School English Teacher, before being distributed along with the Solar Lamp to the target schools.

Prototype Review

Innogetic built a prototype and it was reviewed. My fellow EEF volunteer, former Microsoft colleague, and friend, Jeffrey lives in China and was able to go to the Innogetic office for the review.  He reviewed the construction of the prototype and observed some product testing. The highlights and findings are as follows:

nOverall system looks robust for student use.

¨1 meter drop tested,

¨water resistant,

¨LED is bright enough for reading in dark environment

¨Articulating arm is flexible and easy to use.

¨Battery holds charge for weeks

n¨Innogetic will write an assembly document including photos

¨Innogetic will 100% test subsystems during manufacturing

¨Heavy cloud cover (typical of Zhuhai) can prevent charging. Anecdotally, cloud cover is lighter in in-land provinces.

¨

¨There will be 5% extra parts for spares/defects.

Innogetic will define tool kit for school

Getting funding and Purchase orders

I haven't made new posts in the past month or so, because price and term negotiation is normally confidential between the two parties. I had analyzed the Innogetic quotation for development costs and for unit BOM costs; then I met with the Evergreen Board of Directors, of which I'm a member, to get approval. I assembled a project update and quotation summary in a power point for the board. This was well received, the board was happy with the progress and the prospects. There were some minor issues to clear up like logistics details and how we could use this project for fundraising.  Today, I'm am preparing the Purchase Order for the Faith, the Evergreen President to sign; once Innogetic receives the PO, they will proceed with procurement and building prototypes.

Quotation Analysis

I received the quotation from Innogetic Technologies for the non-recurring development cost; and for the per-unit production cost. I have begun the process of evaluating the quoted costs: I started with the development cost by making my own estimate on the number of person-hours - this estimate is based on my experience and knowledge of what it takes to develop this product. Next I divided their dev cost by the hours to get a per-hour rate. Then compare this estimated rate with professional rates in China. 
To get the production cost, I made my own costed Bill of Materials (BOM) adding in estimated transformation cost (mfg cost), and of course the Chinese 17% VAT tax. This will help me judge the quotation to find out if it is reasonable or if further negotiation is necessary.