Helios

A small solar panel that follows the light. Built for HackPHS 2026, theme "Into the Skies".

Live dashboard | Devpost | Demo video

The idea

A fixed balcony panel only faces the sun for part of the day. Helios tilts and turns a panel toward the brightest light, so the same panel makes more power from the same sky. It runs on a Raspberry Pi 5, costs a few dollars in sensors, and streams everything it measures to a live web dashboard.

How it works

1. Sense. Four light sensors (LDRs) sit at the edges of the panel, read by an ADS1115 ADC.
2. Steer. The Pi compares left vs right and top vs bottom, then drives two hobby servos (pan and tilt) toward the brighter side until the four readings even out.
3. Measure. An INA219 reads the panel's voltage, current and power, so we can compare tracking against a fixed panel.
4. Show. The Pi logs locally and pushes readings to a Vercel + Neon dashboard.

At night the mount returns home. An A/B test mode runs 10 s fixed, then 10 s tracking, to show the gain.

Efficiency

Estimated per day, after the tracker's own energy use is subtracted.

Type	Energy used by Helios	Net gain
Helios (3.6 W)	0.3 Wh	+2.4 Wh (+13%)
Rooftop panel (400 W)	0.05 kWh	+0.28 kWh (+13%)
Solar farm row (40 kW)	0.1 kWh	+33 kWh (+15%)

Dashboard

Live at https://helios-hackphs.vercel.app/. It shows pan and tilt, the four LDR levels, panel voltage, current and power, history charts, the A/B result, and CSV export. The page shows OFFLINE after 5 seconds without data. Lux, temperature and humidity have no sensor in this build and show n/a.

The sample history shown before live data arrives is reconstructed from value ranges observed during the build. It is not a raw recording.

Hardware

Part	Job
Raspberry Pi 5	Runs the control loop
12 V 3.6 W panel (178 x 142 mm)	The thing being aimed
2 x MG90S servos	Pan and tilt
4 x GL5528 LDRs	Direction sensing
ADS1115	Reads the LDRs
INA219	Measures panel power
SSD1306 OLED	Local readout
MB102 breadboard supply	Separate 5 V rail for the servos

Wiring

Function	Pin / address
Pan servo signal	GPIO 12 (hardware PWM)
Tilt servo signal	GPIO 13 (hardware PWM)
I2C	SDA GPIO 2, SCL GPIO 3
INA219	0x40
ADS1115	0x48 (ADDR to ground)
OLED	0x3C

• Servo power comes from the MB102 5 V rail, never from the Pi. Join its ground to a Pi GND pin.
• Each LDR is a divider: 3.3 V, LDR, ADS1115 input, 10k to ground.
• Software limits: pan +/-80 degrees, tilt 15 to 85 degrees. Tuning lives in pi/config.json.

Full schematic: web/public/img/schematic.png.

Run it

Pi

One-time setup:

sudo raspi-config        # Interface Options -> I2C -> Enable
# add to /boot/firmware/config.txt, then reboot:
dtoverlay=pwm-2chan,pin=12,func=4,pin2=13,func2=4
i2cdetect -y 1           # expect 0x40, 0x48, 0x3C

Install and start:

cd pi
python3 -m venv .venv && source .venv/bin/activate
pip install -r requirements.txt
python tracker.py        # add --no-servo to test sensors and OLED only

In a second SSH session, push readings to the dashboard:

python sender.py

Copy pi/.env.example to pi/.env and set MT_API_URL and MT_SHARED_SECRET. The sender survives Wi-Fi drops and sends the backlog when the link returns.

Keys in the tracker terminal: a arm servos, t toggle track/fixed, j/l pan, i/k tilt, x A/B test, c calibrate, q quit.

Dashboard

cd web
npm install
npm run migrate          # create tables in Neon
npm run seed:dry         # preview sample history, then: npm run seed
npm test                 # logic checks
vercel --prod

Set DATABASE_URL (Neon) and INGEST_SECRET in Vercel and in web/.env (see web/.env.example). API routes: /api/ingest (POST, secret required), /api/latest, /api/replay, /api/energy-history, /api/ab, /api/export.

Repo layout

• pi/ - sensing, control, logging and the sender, plus the local energy_history.db
• web/ - everything for the dashboard
  • public/ - the deployed site (index.html, build.html, site.css, img/)
  • api/ - Vercel API routes
  • scripts/ - Neon schema, migration and seed
  • app.py, index.html, helios_logo.png - the local Flask dashboard that reads pi/energy_history.db
• pics/ - build photos
• .gitignore - covers the whole repo

Credits

• Solar panel photo: "Photovoltaic Solar Panel.jpg" by AcornToOak, Wikimedia Commons, CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0). Cropped and straightened.
• Photoresistor photo: "LDR07 Light-dependent CdS photoresistor.jpg" by BenTheWikiMan, Wikimedia Commons, public domain. Cropped.