4-layer marine GPS timing and communication device using nRF52840, u-blox ZED-F9P GNSS with external active antenna via u.FL, 915 MHz LoRa radio, Li-ion battery with USB-C charging, separate clean GNSS LDO and digital 3.3V rail, SPI memory LCD, RGB LEDs, buzzer, and 6-axis IMU. PCB target is a 70 mm circular layout with strict RF zoning, dedicated ground plane, 50 ohm RF traces, physical separation between GNSS and LoRa, and low-noise placement suitable for harsh marine environments.

This is a smart watch project based on E73-2G4M04S1A module with SoC nRF52810 on board. OLED display and coin battery #wearable #nRF52810 #E73 #Ebyte #BLE #referenceDesign

XIAO nRF52840 Breakout with Centered Accelerometer, Precision Mounting Holes, and Additional Battery Connector

Passive BLE tracker locator with ESP32-S3, 2.4-inch TFT UI, USB-C charging, LiPo battery power, GNSS logging, 2.4 GHz BLE/Wi-Fi energy detection, passive BLE advertisement identification in firmware, and optional ADL5904 cellular-band sensing.

Resonate Pendant golden reference design. Board is a 39 mm x 63 mm portrait rectangle with 5 mm corner radii, 2-layer FR4, 0.8 mm thickness, 1 oz copper on both layers, matte black top solder mask, no bottom solder mask, ENEPIG finish, and no silkscreen on either side. Allowed components only: U1 STM32L052C8T6, U2 CH340E, U3 BQ24210DQCT, C1 10uF, C2 4.7uF, C3-C7 100nF, R1 24k, R2 1k, R3 10k, D1 green 0402 LED, MAG1-MAG4 magnetic pads, J1 solar solder pads, J2 battery solder pads, TP1-TP4 test pads. Required top artwork: golden-ratio grid lines and gold circles on F.Cu with mask openings, decorative only, 0.8-1.0 mm width, at least 0.5 mm from active traces. Required bottom artwork: exposed ENEPIG bottom copper split into FREQ_OUT 61.8 percent and GND 38.2 percent with an exact 0.20 mm S-curve isolation gap, no vias through bottom except one PA4-to-FREQ_OUT via at the extreme edge. Functional requirements: MAG1 and J1 VIN feed U3 IN, U3 OUT feeds J2 battery pad and system VBAT, MAG2 to U2 UD+, MAG3 to U2 UD-, MAG4 to common ground, U2 TX to U1 PA10, U2 RX to U1 PA9, U1 PA4 to bottom FREQ_OUT, U1 PA5 to R2 then D1 to GND, U3 ISET to R1 to GND, U3 TS to R3 to GND, decoupling exactly as specified. Prohibited items: external crystal, JST connectors, wireless module, antenna, separate regulator IC, ESD protection IC, USB-C connector, through-hole parts, bottom solder mask, silkscreen, more than three ICs, or any unapproved substitutions.

Portable Raspberry Pi Pico and NEO-6M GPS tracker powered by a single-cell Li-ion battery, with USB-C charging input, CC resistors, and USB-line ESD protection. Designed to support about 65 mA active current and roughly 30 hours from a 2000 mAh cell, following the performance targets from the evaluation paper.

Experimental 21V/5S Li-ion DeWalt battery charger with 21V DC input, relay-switched charge path, tap monitoring, ESP32-WROOM external controller interface, test header, and 2-layer prototype PCB intent.

Two-channel symmetric line follower robot, dual CNY70 sensor front-end with mirrored 2N2222A motor drive stages and central 8V battery input

Bilateral smart running insole data logger using two nearly identical ESP32-S3 pressure-sensing PCBs. Left variant is an ESP-NOW slave without microSD; right variant is the master with microSD logging. Both preserve the 16-zone FSR mux front end, LiPo charging, AP2112K regulation, USB-C charging input, JST battery connector, and the 280mm x 90mm 2-layer low-profile insole form factor.

Compact 2S Li-ion charger for Sony NP-FZ100 battery using DC input, 8.4 V CC/CV charging, automatic termination, reverse polarity, overvoltage, overcurrent, and thermal protection, with defined B+ and B- battery outputs and PCB-buildable component choices.

Cow health-monitoring wearable PCB for a cow-mounted device. Rear strap electronics target 20-25 g and front sensing assembly target about 15 g. Uses an ESP32-based sensor controller, 200 mAh LiPo battery, battery charging circuitry, and interfaces for ammonia, methane, IR temperature, and saliva sensing. Design must tolerate moisture, mucus, debris, vibration, fur contact, and tongue/lick exposure while remaining compact and lightweight for wearable use.

FlowState Headband EVT1 — 4-Channel EEG Calibration Device Closed-loop EEG neurofeedback headband for theta/beta baseline calibration. 4-layer mixed-signal PCB, 40x30mm. Core ICs: - ADS1299-4PAG (TI) — 4-channel 24-bit EEG analog front end, SPI interface, 250 SPS - nRF5340 (Nordic) — Dual-core BLE 5.3 SoC, 128 MHz app core + 64 MHz network core Key requirements: - Separate analog and digital power domains (dual LDO: LP5907 for AVDD, AP2112 for DVDD) - Split analog/digital ground planes with single-point connection - 6 electrode inputs (4 active + 1 reference + 1 DRL) with individual TVS ESD protection on each - LIS2DH12 accelerometer (I2C) for motion artifact detection - MCP73831 USB-C battery charging (300-500 mAh LiPo) - 2.4 GHz chip antenna or PCB trace antenna at board edge with 10mm keepout - Conformal coating for sweat/moisture protection Reference designs: - Analog front-end: TI ADS1299 EVM (SBAS499) - Digital/BLE: Nordic nRF5340 DK reference schematic Critical constraint: Microvolt-level EEG signals — analog input routing and power supply filtering are the highest-priority layout concerns.

Wearable closed-loop ultrasonic monitoring and transcutaneous neuromodulation system based on ESP32-C3, powered from a 7.4 V 1000 mAh LiPo battery with TP4056 charging, MT3608 boost conversion, AMS1117-3.3 regulation, JSN-SR04T ultrasonic sensing, LED and buzzer alerts through a BC547 driver, and a reserved neuromodulation interface for future integration.

Wearable health device prototype schematic with ECG sensing via AD8232, motion sensing via BNO085 or BMI270 IMU breakout, on-board processing using TI TM4C123G LaunchPad or MSPM0G3507 LaunchPad, optional ESP8266 Wi-Fi, LiPo battery charging with MCP73831, regulated 3.3 V power from TPS63031 buck-boost or AP2112 LDO prototype option, and user interfaces including electrode connector, JST battery connector, programming header, and optional on/off switch.

Production-defensible Rev B ear tag tracker using nRF9151 with separate LTE and GNSS antennas, solar-assisted LiPo charging, battery protection, SPI NOR flash, NFC, eSIM, I2C sensors, Tag-Connect SWD, grouped EVT test points, and RF/power zoning on a 40 mm x 24 mm 4-layer PCB.

Misty Pink Replicator schematic finalized for layout handoff with ESP32-S3, USB-C battery charging, T5838 always-on wake microphone, CI1302 backup ASR analog microphone front end, HTEW0154T8 SPI e-ink display, standardized power/test nets, and final ERC-clean baseline.

Gay Teal P.K.E. Meter with MP2650 USB-C battery charger section finalized, including 1.5uH power inductor and current-sense monitoring filter placeholders for later integration.

Gay Teal P.K.E. Meter with MP2650 USB-C battery charger section finalized, including 1.5uH power inductor and current-sense monitoring filter placeholders for later integration.

ESP32 DevKitC-32 Carrier PCB (No Grove, No Battery LED Bargraph, No Button)

Tiny MSR Card Reader - Always-On Battery Low Power, Encrypted Storage + Encrypted SMS

PS5-Diagnose-Power-Supply-Stick - Battery boost 12V + ESP32 control

6x Warm-White 5mm LED Ring (2 constant, 4 flicker) on 4.5 V battery w/ high-side SPST and bussed 6x330 ohm resistor network

The "Green Dot 2040E5" Board is a Node that interfaces RS485 Sensor probes and can log information to the cloud using LoRa Connectivity. It uses the XIAO RP2040 and the LoRa-E5 (STM32WLE5JC) modules from Seeed Studio to do its magic. It also has amazing power management capabilities (Solar charging, Battery protection, etc) that make it very useful for IoT applications #internetOfThings #smartHomeDevices #SeeedStudio #XIAO #LoRa #RP2040 #IoT

3.3V ESP32-S3 Dual 6V Rail MOSFET Board with MCP23017 I2C Expanders, Option C Gate Network, SW2 DPST Rail-Interlock, 2S LiFePO4 Charger/BMS (BQ24618 + BQ29209) with Series Battery Wiring and Charge Integration, and 2×10 RA Headers (#MCP23017_3V3 #OptionC #GateNetwork #RailInterlock #Dual6V #BQ24618 #BQ29209 #2S #LiFePO4 #SeriesBattery #ChargeIntegration #RAHeaders)

Two-Bank 6 V Igniter Firing System with Onboard 2S LiFePO4 Pack, S-8252A Protection, BQ24618 LiFePO4 Charger (3 A, 3.6 V Fast, <50 mA Termination, 3.8 V HPPC, 3.5 V Float), 32 SOT-223 MOSFET Outputs via MCP23017, with Reserved PCB Areas for Dual 26650 Holders, 34-pin IDC, and Barrel Jack Input #LiFePO4 #Battery #BMS