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Download The SolarTrak® Controller System
Transcript
PC Interface Manual and Installation Guide A comparison between the sun angle and the array position is performed by converting the sun angle to array position coordinates (counts) using an equation involving Gear Ratio, defined here as Counts per Radian (radian = angular arc / radius of arc) then adding in a Reference Offset (in counts also) from a fixed zero point established by a Reference Point (RP) indicating where in the mechanical range of motion a particular count number occurs such that: Request Position (counts) = Sun Angle (radians) * Gear Ratio (counts/radian) + Reference Offset (counts) 0 Count Hard Limits West East Zenith 0 Turncount Northern Hard Limit Axis 1 South Axis 2 Reference Offset Axis 1 Reference Offset Axis 2 Southern Hard Limit Elevation Position Map Azimuth Position Detection of Incremental Position Feedback Signals Counts can be detected electronically as a square-wave signal produced by any one of several methods. In general, as the positioning device moves, a contact, either mechanical or solid-state opens and closes producing a change in voltage (from 0V to 5V, rising edge, or 5V to 0V, falling edge) at an input pin on the microcontroller. The controller detects each change of state by sampling the input line at high frequency and, since the controller senses each edge anyway, the standard interpretation is that each edge is a count or double resolution compared to the notion of a ‘cycle’. Full-Cycle (single res.) Interpretation 5V Half-Cycle (double res.) Interpretation Motion 0V Pulse Detected Pulse Detected The motion of a magnet passing a magnetically sensitive reed switch, alternately grounding and releasing a current-limited 5-volt source, activates the typical signal pulse-generator. Also used with a moving magnet is a solid-state device known as a Hall-Effect sensor, which detects the field polarity of the magnet, north or south, and sets the output signal to 0 or 5 volts respectively. A third, and highly precise signal device is the optical encoder. 7
