SCDVM : Solar Cell Characteristic Measurement

RE: SCDVM : Solar Cell Characteristic Measurement

mp2100 — Fri, 13 Aug 2021 20:49:34 GMT

That's a nice tidy design given all the resistors needed. Very informative. Have you moved it into the sun (or bright lighting) to see the power curve shift around with brightness?

RE: SCDVM : Solar Cell Characteristic Measurement

Andrew J — Fri, 13 Aug 2021 18:44:04 GMT

Nice one. It's really frustrating running out of memory on an Arduino when you've put a lot of effort in getting so far..

RE: SCDVM : Solar Cell Characteristic Measurement

neilk — Fri, 13 Aug 2021 16:06:23 GMT

Nice project, Dubbie [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-38b1fbdb-0253-43f8-bd6c-83e6c11ec9d9/contentimage_5F00_1.png:16:16]

I'm mulling over playing with some solar panels; this, or something similar, would be very useful.

Neil

RE: SCDVM : Solar Cell Characteristic Measurement

genebren — Fri, 13 Aug 2021 15:17:37 GMT

Very cool tester! In thinking about the resistive load, I wonder if you could use a single value resistance and then parallel more and more of them as opposed to having a bunch of different resistors. For example, using 40 1K resistors you can develop the following resistive curve:

[View:/resized-image/__size/483x291/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-38b1fbdb-0253-43f8-bd6c-83e6c11ec9d9/contentimage_5F00_208487.png:483:291]

Sure, this might be a little over kill, you could likely achieve the desired resistance range with fewer resistors. The neat thing about this approach is that you can get a fine resistance step in the area of the curve near the peak power point. Using 1K ohm resistors, the step size at 10 resistors is ~20 ohms, or ~5 ohms at 20 resistors. An added bonus to this approach is that as the resistance drops, the effective wattage of the load increases, allow you to test larger solar panels.

Another fairly simple way to do this is to use a Li-Ion battery charger as a load and to vary the charge current with a simple digital resistor. This can provide a wide range of current testpoints. Here is a detailed description of a very similar approach that I used in a smart solar charger: Smart Solar Lighting Project - Detailed design .