Discover Circuits founder Dave Johnson found this broken solar powered path light near a railroad track. Like many engineers who find things and think the parts might one day come in handy, he stuffed it in his pocket.
The big question: Why does broken stuff seem to have a natural affinity for railroad tracks??
Upon closer inspection, he realized that instead of filling the 3-square-inches of available space with solar cells, the unit skimped out, using four skinny cells that yielded an active area of only .83 square inches (28%). Dave’s calculations revealed that while the light would indeed light, it would only be good for about six hours — maybe good enough for London in June but not nearly long enough for the interminable December nights in Colorado where he resides.
His conclusion: “This design stinks. The manufacturer was trying to save money by using only one rechargeable cell, and a very small solar cell area.”
This post originally appeared at sister publication Electronics Weekly MBM blog, where more of Dave’s analysis appears.