🔥 ATTiny84 PWM Heated Gloves Controller

Firmware for a PWM‑controlled heated gloves system powered by 12 V 18650 Li‑ion batteries and carbon fiber heating elements. Built around an ATtiny84 microcontroller with an OLED display and thermistor feedback for both manual and automatic temperature regulation.

---

✨ Features

• PWM power control (0–100%)
• Automatic mode with target temperature regulation (Tautomatic)
• Manual mode with direct duty cycle adjustment
• OLED display (Tiny4kOLED) shows:
  • Battery voltage
  • Estimated power (W)
  • Duty cycle (%)
  • Internal (Tint) & external (Text) temperatures
  • Current mode (Manual / Automatic)
• Battery monitoring via voltage divider; reduces max power when battery < 9 V
• Safety cutoff at Tmax = 45 °C
• EEPROM storage for mode, target temperature, and max power (Pmax)
• Screen auto‑sleep to save power; wake on button press

---

🛠 Hardware

• MCU: ATtiny84
• Display: 128×64 OLED (I²C, Tiny4kOLED)
• Power: 3S 18650 Li‑ion pack (~12 V nominal)
• Heating element: Carbon fiber resistive wire (~4.7 Ω per glove)
• Sensors: 10 kΩ NTC thermistors (Steinhart–Hart in code)
• MOSFET: Logic‑level for PWM control of heater
• Buttons: Two push buttons (Up / Down)
• Voltage divider: R3 = 340 kΩ, R4 = 100 kΩ (battery sense)
• Power regulation: The PCB design includes a reverse‑engineered Mini360 buck converter to step the battery voltage down to a stable 5 V for the ATtiny84, OLED, sensors, and logic.

🖼 Pictures

ATtiny84 pinout (used here)

VCC GND PB0 PA0 PB1 PA1 PB3 10 RST PA2 PB2 PA3 PA7 PA4 13 SCK PA6 11 SDA PA5 12 MISO

---

📦 Dependencies

• TinyI2CMaster
• Tiny4kOLED
• avr/io.h, EEPROM.h (standard AVR/Arduino environment)

---

⚙️ Configuration and constants

• Vcc: 5.02 V (used for ADC voltage calculations)
• gloveResistance: 4.7 Ω (used for power estimate P ≈ (V·duty%)² / R)
• Tmax: 45 °C (safety software cutoff)
• Pmax: Default 100%; auto‑limited to 70% when battery < 9 V
• Screen timeout: 10 s (turns OLED off to save power)
• EEPROM addresses: 0 → automaticMode, 1 → Tautomatic, 2 → Pmax

---

🔧 Build and upload

1. Install ATtinyCore in Arduino IDE or use PlatformIO with ATtiny84 support.
2. Board: ATtiny84; Clock: 8 MHz internal.
3. Wire OLED over I²C (PA6 SDA, PA4 SCK if using SPI pins reference; confirm your OLED’s interface).
4. Compile and upload via ISP (e.g., ArduinoISP) or supported programmer.

---

🎛 Usage

• Manual mode:
  • Up/Down buttons adjust power in 5% steps (0–100%).
• Automatic mode:
  • Maintains Tautomatic; power goes to Pmax below target and 0 above target.
• Settings:
  • Press both buttons to enter.
  • Toggle Manual/Automatic.
  • Set Tautomatic (°C).
  • Set Pmax (%).
  • Values persist via EEPROM.

---

🖥 Display fields

• V: Battery voltage (computed from ADC and divider)
• P: Estimated power (W), using P ≈ (V·duty%)² / R
• D%: Duty cycle (%)
• Text: External temperature (°C)
• T: Internal glove temperature (°C)
• Mode: Manual / Automatic with on‑screen bar indicator

---

🧠 Implementation notes

• Thermistors: 10‑sample averaging; Steinhart–Hart coefficients used directly in code for °C conversion.
• PWM output: PB2 (Arduino pin 8 in code context) via analogWrite; ensure timer compatibility on ATtinyCore.
• Debounce/Timing: Button reads gated by millis() intervals; screen sleeps after inactivity.
• Battery logic: ADC on PA1, scaled with Vcc and divider ratio; reduces Pmax when < 9 V.

---

🔒 Safety

• Validate MOSFET thermal performance and add a fuse/thermal cutoff in hardware.
• Test with a current‑limited bench supply before Li‑ion packs.
• Ensure proper insulation and strain relief for heating elements.
• Do not rely solely on firmware for critical thermal protection.

---

🚀 Future ideas

• Flexible and compact PCB
• Bluetooth control
• Include hardware current/thermal safety cutoff

---

👤 Author

Developed by Marc Prat Plana