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LNSC-2420-Firmware
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Firmware for the LNSC-2420 solar charger. Based on libopencm3.
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Thomas Kolb 49bd9247e0 Average the measurements 
The measurement module now provides averaged measurements. These are
used in some places where accuracy is more important than latency (for
example for the temperature limit, where noise triggered the limit too
early).
 		2021-06-18 23:37:16 +02:00
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README.md

Firmware for the LNSC-2420 Solar Charger

The LNSC-2420 is a PWM-based solar charge regulator for 24 V systems supporting up to 20 A charging current.

Noteworthy features:

  • High-side switching with N-Channel MOSFETs:
    • Gate voltage is provided by a charge pump which doubles the battery voltage.
    • The MOSFETs are controlled using GPIOs.
  • Current and voltage measurement:
    • The solar current, load current, solar voltage, battery voltage and charge pump output voltage are measured using the internal ADC of the STM32F030.
  • Low power usage:
    • The charge pump is disabled if both power FETs are off.
    • Additionally, the microcontroller is put into deep sleep (Stop Mode) if no solar power is available and the battery voltage is in undervoltage protection.
  • LED status display:
    • 6 LEDs show the internal charging and discharging state.
    • The LEDs are controlled using Charlieplexing (i.e. only 3 GPIOs are needed)
  • Protections:
    • Solar panel reverse current
    • Battery overvoltage
    • Battery undervoltage
    • Load current limit

Calibration

The sensing hardware should be quite accurate, but some minor error always remains. They can be compensated via the parameters in src/calibration.h.

To adjust those parameters, first set all CAL_FACTORs to 1000, recompile and flash the firmware. Then watch the RS485 output, which contains all measurements in a line starting with MEAS. Apply a known current/voltage for each measurement and calculate:

                          Actual value
CAL_FACTOR = 1000 * -----------------------
                    Value shown by firmware

Round to the nearest integer and replace the 1000 in src/calibration.h by the calculated value.

Customization

All customizable parameters can be adjusted in src/config.h.

License

The code in this repository (except submodules) is licensed under the MIT license.