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I am making a solar tracker and was checking different methods for Sun Light Sensing. This one is what I was going to use, which is pretty simple arrangement of LDR sensors, which go in shadow if panel is not perpendicular to sunrays.

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However I came across some commercial trackers which use different sensor and arrangement, for eg,

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Can anyone explain how this method works and which sensors are they, because it seems to have some advantage over the first arrangement.

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You can design your circuit with LDRs. The pictures show what I guess to be 3mm DIP Ambient Light Sensors.

I can't see the details of the second picture, but if they are 8 separate sensors, it will be more precise and will drive your solar panel to better levels of light and consequently, higher output power (unless it will be already receiving more than enough light).

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  • \$\begingroup\$ LDRs seem to be pretty mismatched, I even tried calibrating them but i get very diferent values for same amount of light, but using LED as sensor seems promising, as they give large margin difference if sun is not at same angle to them \$\endgroup\$ – Sajid Oct 24 '15 at 16:24
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Both sensors appear to be using LEDs as light detectors. It isn't possible to determine what color of LED they are using, nor is possible to determine what the dispersion angle is. You would have to experiment with various LEDs to see what works best for you.

You may not already know this, but plain ordinary LEDs make decent light detectors. A LED will produce a small DC voltage when exposed to light. The wavelength that the LED responds to is normally the color that the LED is designed to produce.

The 2nd sensor that you show (8 LEDs) is more accurate than the sensor with only 4 LEDs. However, I would point the LEDs that are currently straight up to a 45 degree angle instead of straight up.

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  • \$\begingroup\$ Yes, on further research i found green colour leds are best for sunlight sensing. And the one i tested today gave 0.75uA current so i made an opamp circuit to convert it to voltage. Do you know why using more sensors is better? And how do we wire them, in series? \$\endgroup\$ – Sajid Oct 24 '15 at 15:55

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