4 Board Calibration

The Solar Battery LED Streetlight board is pre-calibrated for the voltage and current input ranges appropriate for each board variant. If the solar input range is increased or decreased for the application, or the battery configuration is changed, the voltage dividers and current monitoring resistors can be adjusted to fully utilize the ADC range of the controller. An Excel-based design tool, included in the download package available at www.microchip.com, contains the calculations for these resistor values.

In production, each board (or at least each board variant/revision) will need to be calibrated using a precision voltage and current source capable of representing the input and output voltage range of the end product. More information can be found in Productizing the Design.

These calibration values are not used by the embedded CPU. They are simply there to make entering real-world numbers (volts and currents) easy for the user of the GUI on the Configure tab. Ultimately, the embedded CPU only cares about ADC count values that represent key voltage thresholds such as input under/overvoltage, pre-charge voltage, CC/CV transition voltage, solar and battery currents, etc. These values are used in the state machines to transition between states when voltage/current thresholds are met.