Greenwatts

How It Works

The SunSwitch sensor is basically an array of LEDs arranged on a curved surface. The sensor array is divided into an east and west array and separated by a vane which cast a shadow. When LEDs are exposed to direct sunlight within their focus angle they produce a small current (micro-amps) and associated voltage which is compatible with TTL inputs.

Tracking - the shadow vane and first row of west LEDs are used for tracking. The shadow alternately covers then exposes the first row of west LEDs. When the first row is exposed to the sun it outputs a small voltage... which turns on a DC motor via a TTL circuit which drives the tracker and sensor in a west direction casting a shadow over the first row of west LEDs causing the voltage to drop and turning off the DC motor. This process repeats about every 60 seconds.

Searching - when resetting in the morning or updating after a cloudy period all the rows of LEDs are used and the end result is a tracking condition as above. If the tracker ended the previous day facing west the rising sun will strike the east most row of LEDs and cause the east DC motor to turn on which will drive the tracker in a east direction ... the first row of east LEDs will drive the tracker about 45 degrees then hand off to the next row of east LEDs which will continue to the next then the final row of east LEDs which is next to the shadow vane... as the tracker continues to move east the vane cast a shadow over the last row of east LEDs causing the east DC motor to stop. The sun then creeps westward and after a few degrees of arc will expose the first row of west LEDs and tracking will begin. A interruption in tracking (cloudy period) will result in the same process as a morning reset but the west LEDs are involved rather than the east LEDs.