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projects:blinker:work_logs:8_solar_cells [2022/03/20 01:07] tjhowseprojects:blinker:work_logs:8_solar_cells [2022/04/17 23:45] (current) tjhowse
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 All of this testing was done on a single 125x125 solar cell. I have another nine of them to experiment with. I would like to see how these cells respond to a CO2 laser. I work with people who built solar racing cars, and so have experience with this kind of thing. We also have a water jet cutter at work, which might be worth a try. All of this testing was done on a single 125x125 solar cell. I have another nine of them to experiment with. I would like to see how these cells respond to a CO2 laser. I work with people who built solar racing cars, and so have experience with this kind of thing. We also have a water jet cutter at work, which might be worth a try.
  
-===== Video =====+==== Unearned success ==== 
 + 
 +I was at Bunnings (a hardware store) for an unrelated reason and I saw some solar-powered garden lights with various configurations of solar cells. They were mostly under AUD$10 so I grabbed an 8-solar-cell LED light on a stake. 
 + 
 +{{:projects:blinker:work_logs:pasted:20220417-233721.png}} 
 + 
 +{{:projects:blinker:work_logs:pasted:20220417-233636.png}} 
 + 
 +{{:projects:blinker:work_logs:pasted:20220417-234440.png}} 
 + 
 +I drilled a small hole in the bezel to make the LED visible from the front. 
 + 
 +I connected the 8 cell panel to a blinker circuit and it generates enough power to overwhelm the voltage limiting zener and the supercap overvolted to 3.1V. I did some experimentation with covering up cells with tape, but quickly realised that dark cells don't pass current. 
 + 
 +{{:projects:blinker:work_logs:pasted:20220417-234033.png}} 
 + 
 +I dug through the polymer coating with a hot air gun and knife to expose a connector and soldered on a wire that bypassed two of the cells. This gave me the following results under direct sun when connected to the blinker: 
 + 
 +{{:projects:blinker:work_logs:pasted:20220417-234304.png}} 
 + 
 +I was pretty happy with that, however it did sneak pretty close to the voltage limit of the supercap. I decided I would go with a 5-cell array for the final version. 
 + 
 +{{ youtube>lZiL-H9wsoI?large }} 
 + 
 +==== Success again ==== 
 + 
 +{{:projects:laser_cutter:pasted:20220331-000734.png}} 
 + 
 +Once I got my [[projects:laser_cutter:overview|laser cutter]] set up, things started to improve again. I collected all of the bigger bits of the failed previous attempts and shot lasers at them at varying intensities, movement speeds and number of passes. I settled on 2 passes at 70% power on my 80W CO2 laser tube moving at 50mm/s, lasering the backside of the cells. This caused the seam to bend upwards slightly providing a guide for the crack. 
 + 
 +{{:projects:blinker:work_logs:pasted:20220403-060140.png}} 
 +First attempt. Note the cut is approximately parallel to the fine white lines. 
 + 
 +{{:projects:blinker:work_logs:pasted:20220403-060227.png}} 
 +More success. 
 + 
 +{{:projects:blinker:work_logs:pasted:20220403-060040.png}} 
 +Repeatable results. 
 + 
 +{{:projects:blinker:work_logs:pasted:20220404-002747.png}} 
 +Soldered up one five-cell array. 
 + 
 +I used some fine copper wire to join the cells. I used leaded solder, a chisel tip, Chipquik SMD291 flux and 270ºC. I dipped the wire in the flux and laid it across the contact on the panel, wet the iron tip with a good amount of solder then swept across the copper while I held it in place. Once I got my technique sorted it was pretty straightforward. 
 + 
 +Holding this cell in diffuse sunlight gave 2.7V open circuit voltage. 
 + 
 +===== Videos ===== 
 + 
 +Failure:
  
 {{ youtube>s49XNyZ3Eqo?large }} {{ youtube>s49XNyZ3Eqo?large }}
 +
 +Success:
 +
 +{{ youtube>lZiL-H9wsoI?large }}
 +
 +{{ youtube>E3jePteZ7Yw?large }}
 +
 +{{ youtube>DGBrjxjcLxw?large }}
  
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projects/blinker/work_logs/8_solar_cells.1647738425.txt.gz · Last modified: 2022/03/20 01:07 by tjhowse