středa 18. března 2015

Goldcaps? Goldcaps!

As promised yesterday, some new toys that arrived recently. I got some solar panels - those are 4.5V and 5V rated ones. The 5V one can actually put over 5.6V on a really bright sunlight, which is - after dropping 0.2V of the forward voltage of a Schottky diode - close to the 5.5V rating of the goldcap, so I am using the 4.5V panel. Then, there are two goldcaps, 1F/5.5V and 22F/2.3V, and finally a sealed lead-acid accumulator, 6V/4Ah.
First thing I tried was a few experiments with the goldcaps and solar panels, of course. I just added the BAT54 Schottky diode and used my incadescent lamp to generate some electricity. The voltage went up nicely and I was watching the 22F goldcap charging - sweet! After removing the light, the voltage begun to drop quickly, and it looked like the self discharge of the goldcap is that high that it won't hold the charge for more than just a few minutes!
After looking up more info on web, I realized that a goldcap is really behaving like that - the charge slowly trickles in and it takes some time for it to reach all the parts of the golcap. To prove that, I let the goldcap with attached panel charge all the day on the balcony. It got charged to 1.9V, and after more than a day, the voltage dropped to 1.78V only. Much better!
I used the 5.5V goldcap with the meteo node. It worked over day, but after nightfall, the voltage dropped pretty quickly and the node only worked for a few hours. I need to create a monitoring and logging tool that isn't dependant on my computer working all the time. Hmmm, a good application for RasPI! If nothing else, I know it works with RF24 *evil grin*.
That's all for today, I need to make plans for further steps. One of them will be finding the best way how to put the solar panels (the 9V ones I have) on the balcony, on a direct sunlight, avoiding my wife's flowers and plants, and the sunshades she puts over the flowers on hot days. That's the trickiest thing.

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