System Architecture
End-to-end data flow from sensors to hospital dashboard
Smart Pad Body Placement
Upper chest placement for reliable ECG, SpO₂ and temperature monitoring
For demonstrations, place the Smart Pad on the upper chest, just below the collarbone. This position provides good skin contact for ECG electrodes and the temperature sensor, and is consistent with common clinical practice for chest-worn vital sign patches.
Technical Specifications
Professional-grade components selected for reliability and accuracy
🔧 ESP32-C3 Mini
Cost-effective RISC-V microcontroller with integrated WiFi and Bluetooth for seamless connectivity.
| CPU | Single-core 160MHz RISC-V |
| Flash Memory | 4MB |
| SRAM | 400KB |
| WiFi | 802.11 b/g/n |
| Bluetooth | BLE 5.0 (100m range) |
| Operating Voltage | 3.0-3.6V |
❤️ MAX30102 PPG Sensor
Integrated pulse oximetry and heart-rate monitor with I2C digital interface.
| Interface | I2C (400kHz) |
| SpO₂ Accuracy | ±2% |
| HR Accuracy | ±3 BPM |
| LED Wavelengths | 660nm (Red), 880nm (IR) |
| Sample Rate | 50-1000 samples/sec |
💓 INA128 ECG Front-End
Custom-built single-lead ECG circuit using instrumentation amplifier and discrete filters.
| Type | Single-lead (custom design) |
| Amplifier | INA128 Instrumentation Amp |
| Output | Analog signal (ADC) |
| Leads | 3-electrode (RA, LA, RL) |
| Bandwidth | 0.5-40 Hz |
| CMRR | 80 dB |
🌡️ DS18B20 Temperature Sensor
Digital temperature sensor with 1-Wire interface.
| Interface | 1-Wire |
| Accuracy | ±0.5°C |
| Range | -55°C to +125°C |
| Resolution | 9-12 bit configurable |
| Conversion Time | 750ms (12-bit) |
Circuit Design & Pin Mapping
Optimized PCB layout for reliable signal acquisition
| Component | Pin | ESP32-C3 GPIO | Notes |
|---|---|---|---|
| MAX30102 | SDA | de class="code-highlight">GPIO1 | I2C Data |
| MAX30102 | SCL | de class="code-highlight">GPIO0 | I2C Clock |
| MAX30102 | INT | de class="code-highlight">GPIO3 | Interrupt (optional) |
| INA128 ECG | OUTPUT | de class="code-highlight">GPIO4 | Analog signal (ADC) |
| DS18B20 | DQ | de class="code-highlight">GPIO5 | 1-Wire, 4.7kΩ pull-up |
| Battery Monitor | VBAT | de class="code-highlight">GPIO6 | ADC for voltage monitoring |
| Status LED | LED | de class="code-highlight">GPIO8 | Built-in LED |
Bill of Materials
Complete component list for replication
| Component | Qty | Unit Price | Total |
|---|---|---|---|
| ESP32-C3 Mini DevKit | 1 | ₹220 | ₹220 |
| MAX30102 PPG Module | 1 | ₹175 | ₹175 |
| INA128 + Discrete ECG Circuit | 1 | ₹120 | ₹120 |
| DS18B20 Temperature Sensor | 1 | ₹75 | ₹75 |
| Li-Po Battery 800mAh | 1 | ₹180 | ₹180 |
| TP4056 Charging Module | 1 | ₹50 | ₹50 |
| PCB Proto Board | 1 | ₹50 | ₹50 |
| 3D Printed Enclosure | 1 | ₹120 | ₹120 |
| Resistors & Misc Components | 1 | ₹50 | ₹50 |
| Strap & Velcro | 1 | ₹80 | ₹80 |
| Assembly & Overhead | 1 | ₹380 | ₹380 |
| DIY Build Cost | ₹1,500 | ||
Validation Checklist
All functionality verified with optimized hardware design
- ✅ I2C communication verified (MAX30102)
- ✅ INA128 ECG circuit operational (discrete design)
- ✅ 1-Wire communication verified (DS18B20)
- ✅ BLE 5.0 data transmission working
- ✅ SpO₂ accuracy ±2% validated
- ✅ Heart rate accuracy ±3 BPM validated
- ✅ Temperature accuracy ±0.5°C validated
- ✅ Battery runtime 8+ hours confirmed
- ✅ PTT-based BP estimation verified
Build Your Own
All schematics, firmware, and documentation are open source. Start building your Smart Vital Monitoring Pad today.