Outdoor Solar Phone Charging Stand

Page last updated 08 Nov 2016, by WB Tan. 3 replies

Introduction:

The Solar Phone Charging Stand is an outdoor mobile phone charging station. A switching regulator will step down 12V input voltage to 5V output voltage for phone charging. It is equipped with a standalone solar PV system that supplies the energy demand of the product. The system intelligent is controlled by mbed NXP LPC1768 microcontroller. The microcontroller will read analog output of the charging circuit’s stunt resistor and derive the current drawn by the phone. System’s temperature can be measured using thermistor. The exhaust fan will turn on when temperature exceeds desired value. All reading is updated visually on a 16x2 LCD display. The standalone solar PV system’s electrical parameter can be extracted from MPPT charge controller via its MODBUS interface using the mbed microcontroller.

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Specification:

  • 5V Phone Charging booth
  • Standalone PV System
  • 54W Monocrystalline Solar PV Panel
  • 100Ah 12V Battery Capacity
  • Charge Controller with MODBUS protocol
  • Generate an average of 296Wh Daily
  • 5 Day of Autonomy
  • Adjustable Solar PV Panel tilting angle
  • Emit zero pollutant
  • Mbed NXP LPC1768 microcontroller updates system's electrical parameter on LCD display periodically

Block Diagram:

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Schematic Diagram:

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Program Flow Chart:

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Additional Notes

All components are provided by Ngee Ann Polytechnic. This is my third projects using the mbed microcontroller. I completed this project alone in less than 3 months. Understanding of MODBUS Protocol is required.

3 comments on Outdoor Solar Phone Charging Stand:

HM Yoong
23 Jul 2013

Good work!

sandip pandey
27 Nov 2013

hi, I have a question. Do u use any load resistor to measure the internal resistance of the battery. If u use any in the circuit could u plz point it out. I have a hard time understanding the shunt (load)resistor.

WB Tan
28 Nov 2013

sandip pandey wrote:

hi, I have a question. Do u use any load resistor to measure the internal resistance of the battery. If u use any in the circuit could u plz point it out. I have a hard time understanding the shunt (load)resistor.

Hi surja25

Yes, i use a load/shunt resistor. My main goal is to find out the amperage value while the phone is charging using an ADC. The shunt resistors for all four charging station are labelled as RSH1.1, RSH1.2, RSH2.1 and RSH2.2 in the schematic diagram. Pardon if my schematic diagram is poorly drawn.

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