Nordic Semiconductor nRF52840
Smart Motorcycle Visor Rain Cleanser
Overview
An aftermarket safety pod for motorcycle helmets that clears rainwater from polycarbonate visors using high-frequency ultrasonic piezoelectric atomization, controlled via Bluetooth.
GuhanSystem architecture
POWER
MCU
SENSOR
ACTUATOR
- BATTERY_PROTECTION → POWER_MANAGEMENT3.7VConnects protected 18650 cell output to the charging and power path management IC
- POWER_MANAGEMENT → STEP_UP_BOOST3.7VSupplies battery voltage to the boost converter input
- POWER_MANAGEMENT → BLE_MCU3.3VProvides regulated 3.3V supply to the BLE MCU (via internal LDO on BQ24075 or separate LDO)
- BLE_MCU → STEP_UP_BOOST3.3VEnables or disables the step-up boost converter for zero quiescent drain when off
- BLE_MCU → ENVIRONMENTAL_SENSOR3.3VI2C communication bus for temperature and humidity telemetry
- BLE_MCU → ULTRASONIC_DRIVER3.3VHigh-frequency PWM signal to drive the gate driver and half-bridge circuit
- STEP_UP_BOOST → ULTRASONIC_DRIVER12VProvides boosted high-voltage rail for the ultrasonic driver stage
- ULTRASONIC_DRIVER → PIEZO_TRANSDUCER12V ACResonant AC drive signals to excite the piezoelectric transducer at 110 kHz
Bill of materials
| Part number | Type | Component | Manufacturer | Package | Qty | Datasheet | Match |
|---|---|---|---|---|---|---|---|
| BQ24075 | POWER | Texas Instruments BQ24075 Autonomous 1-cell Li-ion charger with dynamic power path management for simultaneous charging and operation. | Texas Instruments | QFN16 | 1 | Matched | |
| DW01A | POWER | DW01A + FS8205A Protection Circuit Overcharge, over-discharge, and overcurrent protection for the 18650 Li-ion cell. | FORTUNE | SOT23-6 | 1 | Matched | |
| TPS61088 | POWER | Texas Instruments TPS61088 Steps up 3.7V Li-ion voltage to 10V–12V for efficient piezoelectric drive with output disconnect. | Texas Instruments | — | 1 | Matched | |
| NRF52840-QIAA | MCU | Nordic Semiconductor nRF52840 Handles system logic, Bluetooth 5.3 wireless connectivity, sensor telemetry, and PWM generation. | NORDIC | - | 1 | Matched | |
4 alternatives consideredAI verified | |||||||
| SHT41 | SENSOR | Sensirion SHT41 Measures ambient and visor micro-climate relative humidity to intelligently trigger defogging cycles. | Sensirion | — | 1 | Matched | |
| TC4420 | ACTUATOR | Microchip TC4420 + Infineon IRLML6244PBF High-speed MOSFET driver and power switching stage configured as a half-bridge resonant driver. | Microchip | — | 1 | Matched | |
| TPS61088 | ACTUATOR | 110kHz Piezoelectric Ultrasonic Mesh Atomizer Shatters rainwater droplets into fine mist through the polycarbonate visor. | Texas Instruments | — | 1 | Matched | |
Build guide
5-8 hoursAdvanced
1
Procurement & Preparation
- Source and inventory all raw components including BQ24075, DW01A protection IC, FS8205A MOSFET, TPS61088 boost converter, nRF52840 MCU, SHT41 humidity sensor, TC4420 driver, IRLML6244PBF MOSFET, and 110kHz Piezoelectric Ultrasonic Mesh Atomizer.
- Inspect the dual-layer custom Printed Circuit Board (PCB) designed to house the power path manager, boost converter, and nRF52840 SoC for any manufacturing defects or short circuits.
2
Hardware Assembly & Wiring
- Solder the DW01A protection IC and FS8205A dual N-channel MOSFET onto the battery protection section, then connect the 18650 Li-ion cell to establish the B+, B-, VBAT, and GND interface signals.
- Mount and solder the Texas Instruments BQ24075 power management module to wire up the 3.7V path from the battery protection circuit and output 3.3V to the nRF52840 BLE MCU.
- Install the Texas Instruments TPS61088 step-up boost converter, connecting it to VBAT and GND to provide the 12V_VSYS rail, controlled via the BOOST_EN signal from the nRF52840.
- Integrate the Sensirion SHT41 environmental sensor via the I2C interface (SDA, SCL, 3V3, GND) to the nRF52840 MCU for micro-climate relative humidity tracking.
- Assemble the half-bridge resonant driver stage using the Microchip TC4420 high-speed MOSFET driver and Infineon IRLML6244PBF power MOSFET, linking the 110kHz PWM signal from the nRF52840.
- Connect the 110kHz Piezoelectric Ultrasonic Mesh Atomizer transducer to the driver stage using the 12V AC (DRIVE+, DRIVE-) interface signals.
3
Firmware Setup
- Connect the SWD programmer to the nRF52840 MCU and flash the base bootloader along with the Bluetooth 5.3 stack firmware.
- Program the firmware logic to poll the SHT41 sensor over I2C, evaluate relative humidity thresholds, and generate the precise 110kHz PWM signal to drive the atomizer.
- Implement the BLE GATT service profile for smartphone connectivity, allowing remote manual toggle and telemetry data monitoring of ambient and visor micro-climate conditions.
4
Testing & Calibration
- Perform a quiescent current and power-path test on the BQ24075 and protection circuit to verify safe charging behavior under 5V USB input and seamless transition to battery power.
- Verify the TPS61088 boost converter output stability, confirming it delivers a clean 12V supply to the driver stage when the BOOST_EN signal is asserted high by the nRF52840.
- Analyze the resonant drive signal using an oscilloscope to confirm the 110kHz frequency output from the TC4420/IRLML6244PBF half-bridge stage to the piezoelectric atomizer.
- Perform a functional misting test by exposing the SHT41 sensor to high humidity vapor and confirming that the nRF52840 triggers the atomizer automatically, while also testing manual Bluetooth commands from a smartphone.
Document
Smart Motorcycle Visor Rain Cleanser
An aftermarket safety pod for motorcycle helmets that clears rainwater from polycarbonate visors using high-frequency ultrasonic piezoelectric atomization, controlled via Bluetooth.
Executive Summary
This reference design defines the system architecture, critical component candidates, risk register, and validation path for Smart Motorcycle Visor Defogger. It is a system-level design deliverable; verify critical claims with manufacturer evidence and prototype testing before production release.
Design Overview
Requirements Coverage
| Requirement | Architecture coverage | Status |
|---|---|---|
| High-frequency ultrasonic piezoelectric atomization to shatter rainwater droplets into mist | Pending validation | Needs verification |
| Wireless Bluetooth control via smartphone app or handlebar remote | Pending validation | Needs verification |
| Low-profile modular pod design to minimize wind drag and neck fatigue | Pending validation | Needs verification |
| Powered by a 3.7V 18650 Li-ion battery for all-weather courier operations | Pending validation | Needs verification |
| Item | Details |
|---|---|
| Product Type | Smart Motorcycle Visor Defogger |
| Key Functions | High-frequency ultrasonic piezoelectric atomization to shatter rainwater droplets into mist, Wireless Bluetooth control via smartphone app or handlebar remote, Low-profile modular pod design to minimize wind drag and neck fatigue, Powered by a 3.7V 18650 Li-ion battery for all-weather courier operations |
| Power Source | Li-Ion Battery |
| Connectivity | Bluetooth |
| Size | ultra-compact and lightweight low-profile pod |
| Environment | wearable |
| Difficulty | Advanced |
| Est. Time | 5-8 hours |
System Architecture
Power Topology: Single 3.7V 18650 Li-ion battery feeds the BQ24075 power path and DW01A protection circuit. 3.3V is regulated for the nRF52840 BLE MCU and SHT41 sensor. A synchronous step-up converter (TPS61088) steps up 3.7V to 12V with output disconnect to feed the half-bridge ultrasonic driver and 110kHz piezo transducer.
Module List
| Module ID | Type | Name | Function | Voltage |
|---|---|---|---|---|
| POWER_MANAGEMENT | POWER | Texas Instruments BQ24075 | Autonomous 1-cell Li-ion charger with dynamic power path management for simultaneous charging and operation. | 3.7V |
| BATTERY_PROTECTION | POWER | DW01A + FS8205A Protection Circuit | Overcharge, over-discharge, and overcurrent protection for the 18650 Li-ion cell. | 3.7V |
| STEP_UP_BOOST | POWER | Texas Instruments TPS61088 | Steps up 3.7V Li-ion voltage to 10V–12V for efficient piezoelectric drive with output disconnect. | 10V-12V |
| BLE_MCU | MCU | Nordic Semiconductor nRF52840 | Handles system logic, Bluetooth 5.3 wireless connectivity, sensor telemetry, and PWM generation. | 3.3V |
| ENVIRONMENTAL_SENSOR | SENSOR | Sensirion SHT41 | Measures ambient and visor micro-climate relative humidity to intelligently trigger defogging cycles. | 3.3V |
| ULTRASONIC_DRIVER | ACTUATOR | Microchip TC4420 + Infineon IRLML6244PBF | High-speed MOSFET driver and power switching stage configured as a half-bridge resonant driver. | 12V |
| PIEZO_TRANSDUCER | ACTUATOR | 110kHz Piezoelectric Ultrasonic Mesh Atomizer | Shatters rainwater droplets into fine mist through the polycarbonate visor. | 12V AC |
Power Tree and Signal Interfaces
| From | To | Type | Interface / rail | Voltage |
|---|---|---|---|---|
| BATTERY_PROTECTION | POWER_MANAGEMENT | power | 3.7V | 3.7V |
| POWER_MANAGEMENT | STEP_UP_BOOST | power | 3.7V | 3.7V |
| POWER_MANAGEMENT | BLE_MCU | power | 3.3V | 3.3V |
| BLE_MCU | STEP_UP_BOOST | data | 3.3V | 3.3V |
| BLE_MCU | ENVIRONMENTAL_SENSOR | power | 3.3V | 3.3V |
| BLE_MCU | ULTRASONIC_DRIVER | power | 3.3V | 3.3V |
| STEP_UP_BOOST | ULTRASONIC_DRIVER | power | 12V | 12V |
| ULTRASONIC_DRIVER | PIEZO_TRANSDUCER | power | 12V AC | 12V AC |
Design Schemes
Integrated BLE MCU with Synchronous Boost and Resonant Half-Bridge Piezo Driver ★
High-efficiency, low-profile smart visor defogger using Nordic nRF52840, TI TPS61088 boost converter, and a dedicated resonant driver topology for 110kHz atomization.
Trade-offs: Optimized for minimal PCB footprint and high acoustic energy conversion efficiency at the cost of a slightly more complex high-frequency switching layout.
Key IC selection
main wireless microcontroller
- Need: Execute application logic, Bluetooth 5.3 stack, and generate precise 110kHz PWM signals with low power consumption.
- Class: ARM Cortex-M4 32-bit MCU with integrated 2.4GHz multi-protocol radio
- Shortlist: Nordic nRF52 series, Silicon Labs EFR32BG series
- Pick: Select based on ultra-low sleep current, available peripheral timers for PWM generation, and robust Bluetooth 5.3 certification support.
piezoelectric supply boost converter
- Need: Step up 3.7V Li-ion voltage to 10V–12V with high peak current capability and output disconnect for resonant driving.
- Class: Synchronous boost DC-DC regulator with internal low-Rds(on) switches
- Shortlist: TI TPS61088, Richtek RT4831
- Pick: Select based on switch current limit (>10A peak), adjustable output voltage range, thermal dissipation capability in tight pod enclosure, and output disconnect feature.
high-speed MOSFET driver and half-bridge switch
- Need: Drive the capacitive piezoelectric transducer at 110kHz with minimal propagation delay and fast rise/fall times.
- Class: High-speed single-channel MOSFET driver paired with logic-level N-channel MOSFETs
- Shortlist: Microchip TC4420 + Infineon IRLML6244PBF, Texas Instruments UCC27524 + NXP PMV16XNER
- Pick: Select based on peak output current capability (>6A), minimal gate charge requirements, and small footprint (SOT-23 / WSON packages) to fit the modular pod.
Risk register
| ID | Area | Severity | Detail | Mitigation |
|---|---|---|---|---|
| r1 | thermal | high | The TPS61088 boost converter and TC4420 driver will experience thermal stress inside the sealed, low-profile modular pod during continuous high-power 110kHz ultrasonic atomization. | Ensure thermal vias under the boost converter pad tie into internal copper planes, and implement firmware duty-cycle throttling if temperature sensors indicate overheating. |
| r2 | emi | high | The high di/dt switching at 110kHz by the half-bridge driver and the high-current boost converter can couple electromagnetic noise into the adjacent SHT41 sensor and nRF52840 Bluetooth antenna, degrading wireless link stability. | Use tight component placement with a dedicated ground plane directly underneath the driver stage, add local decoupling capacitors close to the IC power pins, and route sensitive analog/RF traces away from the high-frequency resonant power loop. |
| r3 | mech | med | Vibrations generated by the 110kHz piezoelectric transducer can cause mechanical fatigue and solder joint cracking on neighboring surface-mount components if rigidly coupled. | Isolate the piezo transducer mounting mechanics using dampening gaskets (silicone/elastomer seals) and apply conformal coating over the PCB to absorb high-frequency micro-vibrations. |
Bring-up and Validation Plan
- Power-off inspection and rail resistance checks
- Current-limited first power-up; verify every rail before enabling loads
- Validate interfaces and timing one subsystem at a time
- Run thermal, fault-injection, EMC pre-scan, and endurance tests for the target environment
Key Components
7/7 modules matched to real parts. See the BOM tab for the full component table.
Texas Instruments BQ24075 (BQ24075)
The candidate matches the primary MPN BQ24075 and the preferred manufacturer Texas Instruments.
DW01A + FS8205A Protection Circuit (DW01A)
The candidate matches the primary MPN DW01A and the manufacturer FORTUNE is acceptable.
Texas Instruments TPS61088 (TPS61088)
The candidate matches the primary MPN TPS61088 and the preferred manufacturer Texas Instruments.
Nordic Semiconductor nRF52840 (NRF52840-QIAA)
Candidate 5 (NRF52840-QIAA) is the actual core IC chip matching the primary MPN nRF52840, which is required for integrat
Build Summary
- Difficulty: Advanced
- Estimated time: 5-8 hours
- Tools required: Anti-static mat, ESD wrist strap, Precision soldering iron, Hot air rework station, Digital microscope, Multimeter
See the Build tab for the full step-by-step assembly guide.
Evidence and Limitations
- Confirm part parameters, certifications, and compatibility against current manufacturer documents.
- Treat industry compliance without test or certificate evidence as a compliance gap, not an approval.
- See Reference Images for visual artifacts and Build Guide for detailed assembly and bring-up steps.