Wearable & Biosensor Electronics Design
Low-noise analog front ends, low-power BLE firmware and compact body-worn boards
Wearable and biosensor electronics are the circuits that measure signals from the body, such as ECG, EEG or EMG, and send them to a phone or cloud. Electuni designs the analog front end, power system, firmware and compact PCB for these devices. It is for teams building body-worn sensing prototypes and products.
Design → Prototype → Production
Key Facts: Wearable & Biosensor Electronics
- Signals
- ECG, EEG, EMG
- Front End
- ADS1299-Class AFEs
- Wireless
- Bluetooth LE
- Platforms
- nRF, ESP32, STM32
- Regulatory
- IEC 60601 Test Readiness
- Lead Engineer
- IPC CID+ Certified
What You Get
- System architecture covering sensing, power, wireless and enclosure constraints
- Analog front-end schematic with electrode interface and input protection
- Compact PCB layout prepared for the product's size and wear location
- Low-power firmware with BLE data streaming and power management
- Bill of materials (BOM)
- Bring-up and signal-quality checks on the first prototype boards
- Design documentation that supports later IEC 60601 testing by an accredited lab
How We Approach Wearable & Biosensor Electronics
Wearable biosensor design starts with the signal. ECG, EEG and EMG signals are measured in microvolts to millivolts, so the analog front end, electrode interface and grounding scheme are defined before the rest of the board. Electuni typically builds these front ends around integrated biopotential AFEs such as the ADS1299 class of devices.
Power and size shape every other decision in a body-worn device. The battery, charger, power gating and Bluetooth LE radio are chosen together so the device can stream or log data for the required time in a housing small enough to wear. Firmware and hardware are designed by the same team, so sampling, buffering and radio use are planned against the power budget.
Electuni designs wearable prototypes and products with IEC 60601 test readiness in mind, which means safety and EMC requirements inform the architecture, isolation and layout from the start. Certification testing is performed by accredited test labs. Electuni does not hold ISO 13485 certification and does not perform clinical validation or regulatory submissions.
Technical Constraints and Trade-offs
- Low-noise analog front end: biopotential signals are small, so input-referred noise, ADC resolution, gain and reference design decide whether the signal is usable. Integrated AFEs in the ADS1299 class combine low-noise amplifiers and simultaneous-sampling ADCs for multi-channel ECG and EEG.
- Input protection: electrode inputs connect directly to the body, so they need current limiting, ESD protection and, where required, defibrillation tolerance. Protection parts add leakage and noise, so they are chosen together with the front end.
- Electrode interface: dry, wet and textile electrodes have different contact impedance and drift. Input impedance, bias currents and lead-off detection are set to suit the electrode type the product will use.
- Common-mode rejection: mains interference couples into the body and appears as a large common-mode signal. A driven-right-leg or bias drive circuit, matched input paths and careful layout keep common-mode rejection high.
- Battery life and power gating: the AFE, microcontroller and radio are switched off or into low-power modes whenever they are not needed. Sampling rate, channel count and how often data is sent all trade directly against battery life.
- BLE data streaming and motion artifacts: continuous multi-channel data must fit within Bluetooth LE throughput, so data is buffered, packed or processed on the device. Movement changes electrode contact and creates artifacts, which are reduced through electrode fixation, front-end design and filtering.
Fabrication and Assembly Handoff
- Schematics and PCB layout files, with Gerber or ODB++ fabrication outputs
- Bill of materials with critical analog and protection parts identified
- Firmware repository with build instructions for the chosen microcontroller
- Board bring-up notes and signal-quality test results from the prototype
- Design documentation that an accredited lab can use when planning IEC 60601 testing
Typical project
Wearable ECG with on-device arrhythmia detection
A wearable ECG with on-device arrhythmia detection records the heart's electrical activity through body-worn electrodes and analyses the rhythm on the device itself. A low-noise analog front end captures the ECG, firmware filters the signal and detects heartbeats, and an algorithm flags irregular rhythms. Only results or short segments need to be sent over Bluetooth LE, which reduces radio use and extends battery life. Electuni's founder, Niloy Mondal, has published IEEE research on this topic.
How an Electuni Engagement Works
Step 1
Discovery
Requirements analysis and feasibility study.
Step 2
Architecture
System design, component selection, and risk assessment.
Step 3
Design
Schematic, layout, firmware, and mechanical CAD.
Step 4
Review
DFM/DFT checks and design review with stakeholders.
Step 5
Prototype
Board fabrication, assembly, and firmware bring-up.
Step 6
Handoff
Production files, BOM, and full documentation package.
Tools & Technologies
- Altium Designer
- Analog Front-End Design
- Nordic nRF Connect SDK
- Zephyr RTOS
- BLE Libraries
Wearable & Biosensor Electronics FAQ
What is an analog front end in a biosensor?
An analog front end is the circuit between the electrodes and the digital system. It amplifies very small biopotential signals, rejects interference, filters the signal and converts it to digital data. Integrated biopotential AFEs such as the ADS1299 class combine low-noise amplifiers, ADCs, bias drive and lead-off detection in one chip, which simplifies multi-channel ECG and EEG designs.
Are your wearable designs IEC 60601 certified?
No design is certified until an accredited test lab has tested it. Electuni designs prototypes and products with IEC 60601 test readiness in mind, so isolation, protection, EMC and documentation are considered from the start. Certification testing is performed by accredited labs. Electuni does not hold ISO 13485 certification and does not provide clinical validation or regulatory submissions.
What is a driven-right-leg circuit and why is it needed?
A driven-right-leg circuit measures the common-mode voltage on the body and drives an inverted version back through a separate electrode. This reduces mains interference and improves common-mode rejection in ECG and EEG measurements. Many integrated biopotential AFEs include a bias drive amplifier for this purpose, but the electrode placement and layout still affect how well it works.
How do you extend battery life in a wearable sensor?
Battery life comes from switching parts off when they are not needed. The analog front end, microcontroller and Bluetooth LE radio are power-gated or put into low-power modes, and sampling rate and channel count are set to what the application needs. Processing data on the device and sending results instead of raw signals also reduces radio time.
Can a wearable stream raw biosignals over Bluetooth LE?
Yes, within limits. Bluetooth LE throughput depends on the connection interval, packet length and the phone it connects to. Multi-channel data at high sampling rates can exceed what a link sustains reliably, so firmware buffers and packs samples efficiently. Where the full raw signal is not needed, on-device processing sends features or events instead.
How are motion artifacts handled in wearable ECG and EEG?
Motion artifacts come from changes in electrode contact and cable movement while the wearer moves. They are reduced by secure electrode fixation, short or shielded leads, high input impedance and a well-designed front end. Firmware filtering removes part of the remaining noise, and an accelerometer can help identify periods affected by movement.