Progress: SolarPanel Mechanics Oneof the main difficulties with this project was my lack of experience with draftingtechnical drawing or metal working. Because of this I got help from workcolleagues with the design and construction. I had received a 50 Watt panelfrom L.I.T.
from which dimensions I designed the support structure. Theconstruction exists of a stainless steel beam which is the main support arm ofthe panel, in which a second part is placed, by sliding in a linkage rod into arotatory bearing which is mounted on the base frame. To this set-up are leversadded to which we connect the linear actuators. These allow for the pan andtilt motion of solar panel.Thetechnical drawings and the pictures to get a better idea of what it looks likeshown in fig 3.
1.1. to 3.1.5 The technical drawings were developed with AutocadInventor. Figure4.1.
Solar Energy Tracker (Frame Support) Figure 4.2 Solar Energy Tracker (Base Support) Figure 4.3 Solar Energy Tracker (Panel Frame) Figure 4.4 Solar Energy Tracker (Assembly Elevations) Figure 4.5 Solar Energy Tracker (Assembly Views)Some changeswere made to the original design as we proceeded to build stage as we needed toinclude some element of adjustability to ensure there was no mechanicalobstruction particularly on the pan rotation of panel.
To achieve this wedecided to use T-slot aluminium for the main base support structure. This allowedus to combine other pieces of aluminum without any welding. T-slot aluminum ismodular – i.e., it’s easily changeable. You can move and connect the aluminumprofiles however you’d like, with added accessories like angle connectors.
Imagesof the prototype in the workshop are shown in fig 3.1.7 to 3.1.
9Figure 4.6 Aluminium profileFigure 4.7 Prototype in workshop Figure 4.
8 Prototype base supportFigure 4.9 Prototype frame support Remainingwork to complete mechanical build includes: · finishing welding of stainless frame support ascurrently only tac welded incase of last minute adjustments.· fabrication of aluminium plate to mount solarpanel to support frame for tilt motion.· mounting of actuators and final adjustments oncemovement limits have been identified.· fabrication of transparent electrical junctionbox to house the hardware and mount to base support PCBDesignFigure 4.10 Main Control Board in Multisim Figure 4.11 Main Control Board in Ultiboard Figure 4.
12 Main Control Board in Ultiboard 3D Descriptionof components and I/O: Figure 3.1.7 PIC16F877 MCUPIC16F887 MCUThis is a high-performance RISC CPU, 8-bit CMOS MCU, andhas 8192-word flash memory, 368 bytes SRAM, 256 bytes EEPROM and 35 I/Os. Itsupports up to 20MHz oscillator/clock input and has a wide operating voltagerange of 2.0V-5.5V. Its inbuilt A/D converter has a 10-bit resolution and threeinternal timers.
It supports enhanced USART module, in-circuit serialprogramming (ICSP), 3-wire SPI and I2C. MAX-232This is an integrated circuit which consists of 16 pins andit is a resourceful IC mostly used in the voltage level signal problems.Generally, the MAX-232 IC is used in the RS232 communication system for theconversion of voltage levels on TTL devices that are interfaced with the PCserial port and the Microcontroller. This IC is used as a hardware layerconverter like to communicate two systems simultaneously. ADC0 input is from the voltage divider circuit of the solar panel.This is to ensure the ADC of the PIC does not get damaged with voltage >5volts.
ADC1 input is from the output of the hall effect current sensorchip which detects current flowing through battery circuit. LDR1, LDR2, LDR3and LDR4 inputs are from light dependant resistor circuit. Four LDRs and Four 100K? resistors areconnected in a voltage divider fashion and the output is given to 4 Analoginput pins of PIC. LDRs are used as the main light sensors and sensethe amount of sunlight falling on them. They are divided into top, bottom, leftand right.For east – west tracking, the analog valuesfrom two top LDRs and two bottom LDRs are compared and if the top set of LDRsreceive more light, the vertical servo will move in that direction.
If thebottom LDRs receive more light, the servo moves in that direction.For angular deflection of the solar panel, the analogvalues from two left LDRs and two right LDRs are compared. If the left set ofLDRs receive more light than the right set, the horizontal servo will move inthat direction.If the right set of LDRs receive more light, the servomoves in that direction. ICSPDAT and ICSPCLK are inputs from the ICSP (In-Circuit Serial Programming) PICKit2programmer. The LCDdisplay has two lines of characters, 16 characters per line. Each character iscomposed of matrix of pixels size 5×8. DB0 – DB7, the 8 data bus lines, which performread/write of data.
Vss, Vdd – Voltage supply pins.R/W – Pin writing/reading to/from LCD.RS – Pin selects registers between Instruction Registerand Data RegisterE – “Enabling” pin; when this pin is set tological low, the LCD does not care what is happening with R/W, RS, and the databus lines; when this pin is set to logical high, the LCD is processing theincoming dataVo – Pin for LCD contrast TX_5V is Transmitter Data Input from TTL(Transistor – transistor logic) logic levelRX_5V is Output of Receiver Data from TTL logic levelTX_RS232 is Input of Receiver Data from RS232RX_RS233 is Transmitter Output from RS232 SDA is Serial Data Line and SCL is Serial ClockLine from I2C bus. Figure 4.13 Power board and modular components in Multisim Figure 4.
14 Power board in UltiboardFigure 4.15 Power board in Ultiboard 3D ACS712 is a hall effect currentsensor IC. IP+ and IP- are current sensing inputs from the battery circuit Figure 4.16 Power board and modular components LM1117T is a 5v to 3.
3v voltageregulator used for the voltage supply and logic level comms of the ESP8266chip. VDD is 5V rail and VCC is 3.3v output supply.
ESP8266 module is not capable of converting 5V to 3.3V. Anexternal logic shifter/converter was used as shown in Fig. 3.1.
9. +3.3V, CH_PDand RST pins are kept at 3.3V for normal functioning of ESP8266. Logic-levelconverter is a device that safely steps down 5V signal to 3.3V. Figure 4.17 Logic Level Shifter The HMC5883L sensor is a 3-axis digital magnetometerIC designed for low-field magnetic sensing.
Communication is done through I2C. Figure 4.18 HMC5883L Figure 4.19 L293D Motor driver module L293Dis a motor driver IC designed to provide bidirectional drive currents of up to600-mA at voltages from 4.5 V to 36 V. This can control 2 DC Motors, theirdirection using control lines and their speed using PWM (pulse widthmodulation) Figure 4.20 ESP8266 WiFi module ESP8266 Wi-Fi module isa self-contained system on chip (SoC) with an integrated TCP/IP protocol stackthat can give any MCU access to your Wi-Fi network. ESP8266 is capable ofeither hosting an application or offloading all Wi-Fi networking functions fromanother application processor.
Figure 4.21 LTC4357 and FDB3632 MOSFET This circuit uses the LTC4357 with a FDB3632 MOSFETto replace the Schottky diode. It’s function is to prevent discharge of the battery duringhours of darkness and provide a fast turn-off minimising reverse currenttransients. A shunt regulator is also used which absorbs any excess chargingcurrent to prevent overcharging. Component List 5.1 Voltage dividercircuit QTY Description Supplier 2 2 Way PCB Mount Terminal Block Farnell (1177875) 1 DC Socket Farnell (2450496) 1 100 ?F capacitor LIT 1 100 ?F tantalum capacitor LIT 2 Resistors – 5k and 1k Ohm LIT Table 5.
1 List of thevoltage divider components. 5.2 Battery charging circuit QTY Description Supplier 1 Solar panel – 17V 50W LIT 1 LM317 voltage regulator Farnell (9756027) 1 LTC4357 Special Function IC, Ideal Diode Controller, 9 V to 80 V in Farnell (1432779) IC Adapter, 8-SOIC to 8-DIP Farnell (2476033) 1 Rechargeable Battery, 12 V, Lead Acid, 4 Ah, Farnell (2083824) 1 Diode – 1n4007 Farnell (9565051) 1 MOSFET transistor Farnell (2454149) 1 SMD ADAPTER, 3-SC-73, 3-SOT-223, 3-SIP Farnell (4552600) 1 0.1 ?F Tantulum Capacitor Farnell (187000) 1 Schottky diode – 3A, 50V Farnell (2675380) 1 Resistor – 100 ohms LIT 1 2K Single Turn Trimmer (voltage adjust) Farnell (9354620) Table 5.2 List of the batterycharging circuit components.5.3 Controller Board QTY Description Supplier 1 2 Way PCB Mount Terminal Block (12V Power input) Farnell (1177875) 1 L7805 5V Regulator Farnell (9756078) 1 10 ?F Tantulum Capacitor (5V decoupling) Farnell (9708448) 1 Right angle 6 pin PCB header (ICSP) Farnell (1248172) 1 10Kohm resistor (Vpp isolation resistor) LIT 1 0.1 ?F Tantulum Capacitor (Reset deglitch) Farnell (187000) 1 Tactile Switch (Reset Button) Farnell (1656423) 1 PIC16F887 Farnell (1439541) 1 Crystal Oscillator, 20MHz Farnell (1666982) 1 DIP IC 40 Pin Socket Farnell (1103841) 2 22pF 50 V NPO Ceramic Capacitors Farnell (1141760) 1 Header, 1 ROW, 3 WAY Farnell(3418297) 1 Jumper, 2.
54mm, Black Farnell(9321357) 1 Green LED 5mm 10mA Farnell(1581221) 1 Red LED 5mm 10mA Farnell(1581220) 2 100ohm Resistors LIT 1 PLUG D-type PCB, R/A, 9Way Farnell(1084697) 1 Max232 DIP16 Farnell(1648737) 1 DIP IC 16 Pin Socket LIT 5 1 ?F 25V Tantulum Capacitor LIT 2 1Kohm Resistors LIT 1 Wire-to-Board Connector, Straight, 16 Contacts Farnell(1298788) 1 10K Single Turn Trimmer (Contrast adjust) Farnell(1357152) 1 16 WAY Ribbon Cable Farnell(1207439) 1 16 Way IDC Socket Farnell(1298778) 1 16 R/A Header Farnell(1298797) 1 2×16 LCD Farnell(2063127) 1 Null Modem Cable Farnell(1525913) Table 5.3 Listof the Controller board components. 5.4 Other components QTY Description Supplier 1 ESP8266 ESP-01 ESP01 WIFI Module Ebay 1 Logic level shifter 3.3v to 5v Ebay 1 LM1117 voltage regulator 3.3v Farnell(1469056) 1 8 Inch 12V Linear Actuator Electric Motor – 200mm stroke Ebay 1 10 Inch 12V Linear Actuator Electric Motor – 250mm stroke Ebay 1 ACS712 Current Sensor Hall Module 20A Range Ebay 1 GY-271 HMC5883L Triple Axis Compass Magnetometer Sensor Module Ebay 1 DS1307 I2C RTC Real Time Clock AT24C32 Board Module Ebay 1 · Mini Motor Drive Shield Expansion Board L293D Module Ebay Table 5.4 Various componentsincluding modular boards Detailed Plan of Action Figure 6.1 Project GaantchartThe project overall is on track.
· We are at the final stages of the mechanicalbuild. · The main control board PCB is fully assembled.The plan is to have the power board assembled and fully integrated with themain control board and modular boards by the end of January. · Software development is in progress. References:I.
Bijal Parikh.2012. RS232: Basics, Implementation .ONLINE Available at: https://www.engineersgarage.
com/articles/what-is-rs232Accessed 01 January 18.II. www.alternative-energy-tutorials.
com.2017. Photovoltaic Solar Cells. ONLINEAvailable at: http://www.alternative-energy-tutorials.
com/solar-power/photovoltaics.html III. Raj Bhatt. 2012.
A brief overview of Allegro ACS712 current sensor. ONLINEAvailable at: http://embedded-lab.com/blog/a-brief-overview-of-allegro-acs712-current-sensor-part-1/ IV. www.linear.
com. 2017 LTC4357Solar Panel Charging 12V Battery Through Ideal Diode to Prevent Back Feeding. ONLINEAvailable at: http://www.linear.com/solutions/1465 V. Bilal Malikuet.
2017. I2C Communication with PIC Microcontroller. ONLINEAvailable at: http://microcontrollerslab.com/i2c-communication-pic-microcontroller/