Computing stuff tied to the physical world

Solar… again – first results

In Software on Jan 23, 2013 at 00:01

Sorry for keeping you in suspense after presenting yesterday’s code. I had to let this run for a few days to collect enough data worth graphing…

Some raw output:

L 15:01:00.818 usb-A40117UK OK 20 90 27 224 25 128 26 224 26
L 15:02:01.232 usb-A40117UK OK 20 68 27 224 25 128 26 224 26
L 15:03:01.663 usb-A40117UK OK 20 64 27 224 25 128 26 224 26
L 15:04:02.075 usb-A40117UK OK 20 64 27 222 25 127 26 224 26
L 15:05:02.486 usb-A40117UK OK 20 64 27 195 25 128 26 224 26
L 15:06:02.901 usb-A40117UK OK 20 64 27 192 25 123 26 224 26
L 15:07:03.314 usb-A40117UK OK 20 63 27 192 25 124 26 224 26
L 15:08:03.728 usb-A40117UK OK 20 38 27 192 25 111 26 224 26
L 15:09:04.140 usb-A40117UK OK 20 32 27 192 25 104 26 224 26
L 15:10:04.557 usb-A40117UK OK 20 32 27 169 25 99 26 224 26

And here some readings with DIO1 turned on:

L 16:01:24.894 usb-A40117UK OK 20 30 51 0 51 128 51 32 51
L 16:02:25.293 usb-A40117UK OK 20 159 51 128 51 0 52 160 51
L 16:03:25.677 usb-A40117UK OK 20 0 52 224 51 107 52 0 52
L 16:04:26.061 usb-A40117UK OK 20 64 52 55 52 192 52 96 52
L 16:05:26.461 usb-A40117UK OK 20 128 52 113 52 0 53 160 52
L 16:06:26.849 usb-A40117UK OK 20 192 52 160 52 61 53 192 52
L 16:07:27.224 usb-A40117UK OK 20 224 52 192 52 96 53 0 53
L 16:08:27.622 usb-A40117UK OK 20 0 53 237 52 128 53 32 53
L 16:09:28.011 usb-A40117UK OK 20 32 53 12 53 160 53 64 53
L 16:10:28.406 usb-A40117UK OK 20 64 53 32 53 192 53 96 53

In decimal, this is what I see:

a0: 13952 a1: 13914 a2: 14144 a3: 14017

Here are the first eight hours after sunset – no energy coming in at all, just conditioning:

a4-19jan

Top to bottom: orange = 2 MΩ, red = 20 MΩ, blue = 2-C 200 kΩ, green = 1-C 200 kΩ. Some variation probably due to resistor / supercap tolerances.

Since we’re measuring half the voltage of the supercaps, you can see that they have all reached around 2.8V at this point. The interesting bit will be to see whether the voltage ever rises in the time between DIO1 “on” cycles – indicating a charge surplus!

Here’s the next 24 hours, only the 2 and 20 MΩ loads benefit from this cloudy winter day:

a4-20jan

Another day, some real sunlight, not enough yet to survive the next night, even w/ 20 MΩ:

a4-22

Note that the only curves which hold any promise, are the ones which can permanently stay above that hourly on/off cycle, since that DIO-pin top-up won’t be there to bail us out when using these solar cells as a real power source.

I’ll leave it for now – and will collect data for some more days, or perhaps weeks if there’s any point with these tiny solar cells. Will report in due time … for now: patience!

PS. Note that these fingernail-sized CPC1824 chips are a lot more than just some PV material in an SOIC package. There appears to be a switching boost regulator in there!

  1. Glad you are working on this again. Very interesting.

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