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--- projects:blinker:work_logs:9_resin_casting [2022/04/17 10:20] – created tjhowse
+++ projects:blinker:work_logs:9_resin_casting [2022/04/17 23:55] – tjhowse
@@ Line 5: / Line 5: @@
 ===== The Plan =====
+I wanted to run a medium-duration test of the electrically-complete blinker before going through all the trouble and expense of encasing it in aluminium and glass. I decided to cast the electronics in transparent resin. This would be reasonably mechanically and chemically robust, but it would degrade in sunlight over a few years, turning yellow and crumbling. This would give me a test good enough to check for any drastic short-term problems with the electronics.
+===== The Results =====
+==== Success ====
+{{:projects:blinker:work_logs:pasted:20220417-224929.png}}
+I bought this resin from bunnings. It's a styrene/polyester resin with a MEK catalyst.
+I cut out a cardboard box on the laser cutter and lined it with gladwrap.
+{{:projects:blinker:work_logs:pasted:20220417-225114.png}}
+[[projects:blinker:work_logs:8_solar_cells|Solar cell]] invested.
+{{:projects:blinker:work_logs:pasted:20220417-225134.png}}
+Not too bad!
+I was reasonably happy with this result. There is some white discolouration on the solar cells visible in that photo. That discolouration did not exist when I took the panel out of the mould. It formed shortly after I put it in the sun for this test. It seems to have been formed by some combination of:
+  * UV radiation,
+  * Heat,
+  * Resin,
+  * Flux, and/or
+  * Solder.
+In direct sunlight this panel generates 3.1V open circuit voltage, 190mA closed circuit current. That was about double the current I was anticipating. This caused me mild concern as the voltage limiting zener might not be able to keep the voltage down. I could add more in parallel to pass more overvoltage current, but that would increase the passive energy loss in the system [[projects:blinker:work_logs:6_power_consumption_testing#conclusions|considerably.]]
+I soldered it to a blinker circuit and put it in the sun:
+{{:projects:blinker:work_logs:pasted:20220417-234821.png}}
+Awesome!
+I was puzzling over why the voltage dropped off so quickly. I wanted to check whether it was panel degradation related to the discolouration or due to the panel heating up inside a pretty good thermal insulator. I put the whole shebang in the freezer for a while to see if that had any effect.
+{{:projects:blinker:work_logs:pasted:20220417-235051.png}}
+Dubious?
 ==== Failure ====
-===== Videos =====
+==== Videos ====
 [<6>]