Hybrid-Solar-Yield-Maximizer--Team-Helios-

Control systems project, It involves the software + hardware implementation of a hybrid solar yield maximizer

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HELIOS – Hybrid Logic Solar Yield Maximizer

Closed-Loop Dual-Axis Solar Tracking System

Team HELIOS | Control Systems Project Review | School of Electronics Engineering, VIT

Team Members

Name Reg. No. Role
Tanuj (Lead) 24BEC0539 System Architecture & Hybrid Logic Algorithm
Srujan Pratap Powar 24BVD0077 Embedded Firmware & IoT Integration
Tarun K 23BEC0277 Data, Documentation & Literature Survey
Praveen Rajan T 23BEC0421 Power Systems & Battery Management
AL Humd 24BVD0140 Mechanical Design & Servo Mounting

Table of Contents

  1. Project Overview
  2. File Structure
  3. Bill of Materials
  4. Circuit Assembly Guide
  5. Software Setup (PlatformIO)
  6. Running the Project
  7. Configuration & Tuning
  8. System Architecture
  9. Troubleshooting
  10. Demo

1. Project Overview

Fixed solar panels lose up to 40% efficiency as the sun moves across the sky. The HELIOS system solves this by continuously aligning a solar panel perpendicular to incoming sunlight using a closed-loop, dual-axis tracking algorithm.

Key Innovation – "Hybrid Logic" with Deadband Damping: Standard LDR-based trackers suffer from the "Hunting Effect" — constant micro-movements in cloudy or diffuse light that waste motor energy and negate solar gains. Our Hybrid Logic system applies a threshold-based deadband: the servo only moves when the LDR differential exceeds a configurable threshold, eliminating jitter entirely in low-contrast conditions.

Expected Performance:

  • Static panel baseline: ~15–20% yield
  • Single-axis tracking: ~31% yield improvement
  • This system (dual-axis + hybrid logic): ~38%+ yield improvement over static

2. File Structure

helios_project/
│
├── platformio.ini          ← PlatformIO project config (board, libraries, port)
│
├── include/
│   └── config.h            ← ALL pin assignments & tuning constants (edit here)
│
├── src/
│   └── main.cpp            ← Main firmware (tracking logic, servo control, telemetry)
│
└── README.md               ← This file

Important: Never hardcode GPIO pins or constants in main.cpp. All configuration belongs in include/config.h.

3. Bill of Materials (BOM)

# Component Specification Qty Notes
1 ESP32 DevKit v1 Dual-core 240 MHz, 4 MB Flash, built-in WiFi/BT 1 Any 38-pin ESP32 DevKit works
2 SG90 Micro Servo 5V, 180° rotation, ~1.8 kg·cm torque 2 One per axis (Azimuth + Elevation)
3 LDR (GL5528) 10–20 kΩ in daylight 4 Quadrant array
4 Resistor – 10 kΩ 1/4 W, 5% 4 Pull-down for each LDR
5 INA219 Module I2C, ±3.2 A current, 0–26 V bus 1 Current/Voltage monitoring
6 Solar Panel 12 V, 5 W, ~417 mA short-circuit 1 Small mono/poly crystalline
7 Li-ion Battery Pack 7.4 V (2S), ≥2000 mAh 1 Powers servos + ESP32
8 Voltage Divider 100 kΩ + 10 kΩ resistors 1 Scales 12 V panel → ADC-safe 1.1 V
9 LM7805 / AMS1117-3.3 5 V regulator (for servo rail) 1 Or use a 5V BEC/buck converter
10 Breadboard (full-size) 830 tie-points 1 Prototyping
11 Jumper Wires Male-Male, Male-Female ~30 Assorted lengths
12 USB-to-Serial adapter CP2102 or CH340 (usually on DevKit) 1 For flashing via USB
13 Small separator / baffle Cardboard or 3D-printed cross 1 Divides LDR array into 4 quadrants

Optional:

  • 100 µF electrolytic capacitor across the servo 5 V rail (reduces voltage spikes)
  • 3D-printed pan-tilt mount for the servos and panel

4. Circuit Assembly Guide

4.1 LDR Quadrant Array

Build a voltage divider for each LDR:

3.3V ────┬──── [LDR] ────┬──── ADC Pin (GPIO 34/35/32/33)
         │               │
         └───────────────┤
                         │
                       [10kΩ]
                         │
                        GND

When light increases, LDR resistance drops → voltage at ADC pin rises → higher ADC reading.

Physical LDR Arrangement:

Mount the 4 LDRs in a 2×2 grid with a cross-shaped baffle (a folded piece of cardboard 2–3 cm tall) between them. This ensures each LDR sees only its own quadrant of the sky:

  ┌──────┬──────┐
  │  TL  │  TR  │   GPIO34    GPIO35
  │(34)  │ (35) │
  ├──────┼──────┤  ← Cross baffle (2–3 cm tall)
  │  BL  │  BR  │   GPIO32    GPIO33
  │(32)  │ (33) │
  └──────┴──────┘

Wiring Summary:

LDR Position ADC Pin GPIO#
Top-Left ADC1_CH6 GPIO 34
Top-Right ADC1_CH7 GPIO 35
Bottom-Left ADC1_CH4 GPIO 32
Bottom-Right ADC1_CH5 GPIO 33

GPIO 34, 35, 36 are input-only on ESP32 — perfect for ADC, no pull-ups/downs.

4.2 Servo Motors (SG90)

Each SG90 has 3 wires:

SG90 Wire Colour Connect To
Signal Orange/Yellow GPIO (13 = Azimuth, 12 = Elevation)
Power Red 5 V rail (from regulator, NOT 3.3 V)
Ground Brown/Black Common GND

Warning: Never power SG90 servos directly from the ESP32's 3.3 V pin — they require 5 V and draw up to 500 mA stall current. Use a 5 V regulator or a dedicated BEC.

Mechanical Setup:

  • Servo 1 (Azimuth, GPIO 13): Rotates the platform left/right (East–West sun tracking)
  • Servo 2 (Elevation, GPIO 12): Tilts the platform up/down (altitude tracking)
  • Mount the panel on a pan-tilt bracket: Elevation servo is on the rotating arm of the Azimuth servo

4.3 INA219 Current/Voltage Sensor

The INA219 is placed in series with the solar panel's positive output lead:

Solar Panel (+) ──→ [INA219 VIN+] ──[Shunt]──[INA219 VIN-] ──→ Load (+)
Solar Panel (−) ──────────────────────────────────────────────→ Load (−)

I2C Connections:

INA219 Pin ESP32 Pin
VCC 3.3 V
GND GND
SDA GPIO 21
SCL GPIO 22

Default I2C address: 0x40 (both A0, A1 pins floating/GND).

4.4 Voltage Divider (Panel Voltage Monitoring)

To safely read the 12 V panel voltage on the ESP32's 3.3 V-tolerant ADC:

Panel (+12V) ──[100kΩ]──┬──[10kΩ]── GND
                         │
                       GPIO36 (VP)

Scaling factor: V_panel = V_adc × (100 + 10) / 10 = V_adc × 11

4.5 Power Supply

7.4V Li-ion Pack
        │
        ├──→ LM7805 (5V regulator) ──→ Servo 5V Rail + ESP32 VIN
        │
        └──→ Solar Panel charges the battery via a TP4056/BMS module

Alternatively: use a small 5V 2A buck converter (MP1584/LM2596 module) instead of the LM7805 for better efficiency.

4.6 Full Wiring Reference Table

Signal ESP32 GPIO Notes
LDR Top-Left GPIO 34 Input-only ADC, 10kΩ pull-down
LDR Top-Right GPIO 35 Input-only ADC, 10kΩ pull-down
LDR Bottom-Left GPIO 32 ADC, 10kΩ pull-down
LDR Bottom-Right GPIO 33 ADC, 10kΩ pull-down
Servo Azimuth Signal GPIO 13 PWM output
Servo Elevation Signal GPIO 12 PWM output
INA219 SDA GPIO 21 I2C
INA219 SCL GPIO 22 I2C
Voltage Divider GPIO 36 Input-only ADC (VP)
5V Rail VIN / 5V Pin From regulator to ESP32 and servos
GND GND Common ground for all components

5. Software Setup (PlatformIO)

5.1 Prerequisites

Install the following in order:

Step 1 – Install Visual Studio Code Download from: https://code.visualstudio.com/

Step 2 – Install PlatformIO IDE Extension

  1. Open VS Code
  2. Click the Extensions icon (Ctrl+Shift+X)
  3. Search for "PlatformIO IDE"
  4. Click Install and wait for it to complete
  5. Restart VS Code when prompted

Step 3 – Install Python (required by PlatformIO) Download Python 3.8+ from: https://www.python.org/downloads/ During install, check "Add Python to PATH"

5.2 Opening the Project

  1. Open VS Code
  2. Click File → Open Folder
  3. Navigate to and select the helios_project/ folder
  4. PlatformIO will auto-detect platformio.ini and configure the project

5.3 Installing Libraries

PlatformIO downloads all required libraries automatically from platformio.ini:

ESP32Servo       v0.13.0    (Servo motor control for ESP32)
Adafruit INA219  v1.2.3     (Current/Voltage sensor)
Adafruit BusIO   v1.16.1    (I2C/SPI abstraction dependency)

To trigger a manual library install/update:

  • Click the PlatformIO icon (alien head) in the left sidebar
  • Go to Libraries → Install if needed, or simply build the project (libraries auto-install on first build)

6. Running the Project

Step 1 – Connect the ESP32

  1. Connect the ESP32 DevKit to your computer via USB
  2. The driver should install automatically (CP2102 or CH340)
    • If not: download CP210x driver from Silicon Labs, or CH340 driver from WCH
  3. Note the COM port:
    • Windows: Device Manager → Ports (COMx)
    • Linux: ls /dev/ttyUSB*
    • macOS: ls /dev/cu.*

Step 2 – Configure the COM Port (if needed)

Open platformio.ini and uncomment the appropriate upload_port line:

; Windows:
upload_port = COM3

; Linux:
upload_port = /dev/ttyUSB0

; macOS:
upload_port = /dev/cu.SLAB_USBtoUART

Step 3 – Build the Firmware

In VS Code with PlatformIO:

  • Press Ctrl+Shift+P → type PlatformIO: Build → Enter
  • Or click the ✓ (checkmark) button in the PlatformIO toolbar at the bottom

Wait for: [SUCCESS] Took X.XX seconds

Step 4 – Upload to ESP32

  • Press Ctrl+Shift+P → type PlatformIO: Upload → Enter
  • Or click the → (arrow) button in the PlatformIO toolbar

If upload fails with "A fatal error occurred":

  • Hold the BOOT button on the ESP32 while clicking Upload
  • Release BOOT once "Connecting..." appears in the terminal

Step 5 – Open Serial Monitor

  • Press Ctrl+Shift+P → type PlatformIO: Monitor → Enter
  • Or click the plug icon in the PlatformIO toolbar
  • Baud rate: 115200 (already set in platformio.ini)

You should see:

====================================
  HELIOS – Solar Yield Maximizer
  VIT Control Systems Project
====================================

[SERVO] Initialized at center position (90°/90°).
[INA219] Current/Voltage sensor ready.
[BOOT] System ready. Entering tracking loop.

─────────────── HELIOS Telemetry ───────────────
  LDR Raw  |  TL: 2341  TR: 1820  BL: 2290  BR: 1750
  Servos   |  Azimuth:  87°   Elevation:  91°
  Power    |  V: 11.45 V   I: 124.3 mA   P: 1423.1 mW
  Tracking |  Est. Incidence Angle: 3.1°  Cos-Eff: 99.9%
────────────────────────────────────────────────

7. Configuration & Tuning

All tunable parameters are in include/config.h. Do not edit main.cpp for adjustments.

Key Parameters to Tune in the Field

Parameter Default Effect
DEADBAND_THRESHOLD 100 Raise (150–200) in cloudy areas to reduce hunting. Lower (50–80) for precise sunny-day tracking.
STEP_DEG 1 Increase (2–3) for faster tracking at the cost of smoothness.
NIGHT_THRESHOLD 150 Raise if system incorrectly detects night during overcast days.
LOOP_DELAY_MS 500 Increase to reduce motor wear; decrease for faster response.
SERVO_MIN_DEG / SERVO_MAX_DEG 10 / 170 Adjust based on your mechanical mount's physical limits to avoid servo binding.
SERVO_NIGHT_PARK_AZ 60 Set to the azimuth angle pointing East for your installation location.

Calibration Procedure

  1. Place the system in direct sunlight
  2. Open the Serial Monitor
  3. Observe the LDR raw values — all four should be roughly equal when the panel is perfectly aligned
  4. If they are significantly unequal at what you believe is correct alignment, adjust DEADBAND_THRESHOLD or check LDR sensor placement

8. System Architecture

┌──────────────────────────────────────────────────────────┐
│                     SOLAR PANEL (12V 5W)                 │
│                          ↓ light                         │
│  ┌──────────────────────────────────────────────────┐    │
│  │       4× LDR Quadrant Array (TL, TR, BL, BR)     │    │
│  └───────────────────┬──────────────────────────────┘    │
│                       │ ADC readings (0–4095)             │
│  ┌────────────────────▼────────────────────────────────┐  │
│  │              ESP32 DevKit v1                         │  │
│  │                                                      │  │
│  │  1. Sample LDRs (8× averaged)                       │  │
│  │  2. Calculate H/V differential errors               │  │
│  │  3. Hybrid Logic:                                   │  │
│  │     if |error| > DEADBAND_THRESHOLD → move servo    │  │
│  │     else → hold position (anti-hunting)             │  │
│  │  4. Clamp to [10°, 170°] servo limits               │  │
│  │  5. Write PWM to SG90 servos                        │  │
│  │  6. Read INA219 (V, I, P)                           │  │
│  │  7. Print telemetry to Serial @ 115200 baud         │  │
│  └────────────────┬──────────────────┬─────────────────┘  │
│                   │                  │                     │
│     ┌─────────────▼──────┐  ┌────────▼──────────┐        │
│     │  SG90 Azimuth      │  │  SG90 Elevation   │        │
│     │  (Horizontal/X)    │  │  (Vertical/Y)     │        │
│     └────────────────────┘  └───────────────────┘        │
│                                                            │
│  INA219 ──I2C──→ ESP32  (monitors panel V, I, P)          │
│  7.4V Li-ion Battery Pack  →  5V Regulator → System       │
└──────────────────────────────────────────────────────────┘

Control Law (Hybrid Logic)

topAvg   = (LDR_TL + LDR_TR) / 2
botAvg   = (LDR_BL + LDR_BR) / 2
leftAvg  = (LDR_TL + LDR_BL) / 2
rightAvg = (LDR_TR + LDR_BR) / 2

errElevation = topAvg  - botAvg     // + → sun is above panel normal
errAzimuth   = leftAvg - rightAvg   // + → sun is to the left

IF |errElevation| > DEADBAND_THRESHOLD:
    posElevation ± STEP_DEG

IF |errAzimuth| > DEADBAND_THRESHOLD:
    posAzimuth ± STEP_DEG

Power output relationship:

P_actual = P_max × cos(θ)

Where θ is the incidence angle between sun rays and panel normal. The closed-loop system minimises θ → maximises P_actual.

9. Troubleshooting

Symptom Likely Cause Fix
Upload fails: "A fatal error occurred" ESP32 not in boot mode Hold BOOT button during upload
Serial Monitor shows garbled text Wrong baud rate Set monitor to 115200
Servos jitter constantly Deadband too low Increase DEADBAND_THRESHOLD to 150–200
Servos don't move at all Wrong GPIO or power issue Check GPIO 12/13; verify 5V on servo rail
INA219 not found Wrong I2C address or wiring Check SDA→21, SCL→22; verify 3.3V to INA219 VCC
LDR values all 0 Pull-down resistors missing Add 10kΩ from ADC pin to GND
LDR values all 4095 Short circuit or no resistor Check resistor values and orientation
System parks at night in daylight Night threshold too high Lower NIGHT_THRESHOLD to 80–100
Panel doesn't track East→West Azimuth servo polarity reversed Swap the += and -= in hybridLogicControl() for Azimuth

10. Demo

Download to view

HELIOS Team – VIT School of Electronics Engineering – Control Systems Project Review

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