This design implements a USB security token powered by an STM32 microcontroller. The device is engineered for compactness and efficient PCB integration while ensuring robust security features. Key elements of the design include: - **Microcontroller Core:** A STM32F103T8U6 serves as the primary processing unit, handling USB communication and security protocols. - **USB Interface:** A USB-A plug provides connectivity to the host. Dedicated net portals ensure proper routing of the VBUS, D+, D–, and ground signals. - **Power Regulation:** A low-dropout regulator supplies a stable 3.3V operating voltage, ensuring low noise and proper current supply to the microcontroller and peripherals. - **Signal Conditioning and EMI Filtering:** An EMI filter is used to maintain signal integrity and reduce interference while preserving the security token’s functionality. - **Synchronous Elements:** A ceramic resonator is incorporated to provide a precise clock source for USB data transfer and microcontroller operations. - **Additional Components:** Surface-mount resistors, capacitors, and LED indicators are deployed to ensure proper conditioning, decoupling, and status feedback. Their compact 0402 packages facilitate a highly integrated design. - **Connectivity and Net Portals:** Custom net portals are used throughout the schematic to streamline connectivity and PCB layout, keeping the design modular and easy to modify. This USB security token is designed with industry-standard components and robust connectivity to ensure secure, reliable operation in portable security applications. #USBToken #STM32 #PCBDesign #SecurityTechnology #PortableSecurity #Microcontrollers #USBInterface #PowerRegulation #EMIProtection #CompactDesign

Have you ever wanted to wake up to one of the most energizing scents? Have you ever wanted that cup of energy in your hands before you even slide out of your covers? Well want no further! Introducing the Coffee Waker; The knight of your nightstand, a coffee maker alarm clock with one soul purpose, to quickly and scrumptiously wake you up. This is the Coffee Waker Main board. It contains an ESP32-S3, 16 bit Load Cell ADC, 16 bit MP3 DAC, 120V heater cartridge relay, and 12C wakeup light convector.

AquaTimer is a programmable timer for 12V devices such as lighting, solenoid valves or pumps not only for aquariums. It has three switchable channels for currents up to 2A each and up to 5A in total. Connected lighting can be dimmed if desired and slowly faded in and out to simulate sunrises and sunsets. The internal RTC of the ATtiny is used as a clockwork in conjunction with a 32.768kHz crystal. A backup battery keeps the clock running even if the external power supply is interrupted. Settings are made using three buttons and the OLED display.

The Texas Instruments MSP430FR604x and MSP430FR603x family comprises highly integrated ultrasonic sensing and measurement system-on-chips (SoCs) designed specifically for water and heat metering applications. The featured components, including MSP430FR6047, MSP430FR60471, MSP430FR6045, MSP430FR6037, MSP430FR60371, and MSP430FR6035, deliver best-in-class ultrasonic water flow measurement with ultra-low power consumption. These microcontrollers excel with an active mode current consumption of approximately 120 µA/MHz and a standby mode power draw as low as 450 nA with a real-time clock (RTC) enabled. Key functionalities include a high-precision differential time-of-flight (dTOF) accuracy of less than 25 ps, integrated analog front-end, programmable pulse generation (PPG), and an analog comparator. They also interface directly with standard ultrasonic sensors up to 2.5 MHz and feature up to 256KB FRAM, robust RAM options, and integrated LCD drivers for up to 264 segments. The embedded low-energy accelerator (LEA) enhances digital signal processing capabilities, making these components ideal for battery-powered metering solutions. Peripherals include multiple enhanced serial communication interfaces, high-performance ADCs, DMA controllers, and a suite of timers and encryption modules. These features combine to offer a powerful solution for high-accuracy, low-cost, and ultra-low-power metering applications.

Running LED circuit that utilizes a 555 clock output and a decade counter. It runs when the push-button is held down and then slowly stops once it is released.

Seeed Studio XIAO ESP32C6 is powered by the highly-integrated ESP32-C6 SoC, built on two 32-bit RISC-V processors, with a high-performance (HP) processor with running up to 160 MHz, and a low-power (LP) 32-bit RISC-V processor, which can be clocked up to 20 MHz. There are 512KB SRAM and 4 MB Flash on the chip, allowing for more programming space, and binging more possibilities to the IoT control scenarios.

This is a great battery-backed real time clock (RTC) that allows your microcontroller project to keep track of time even if it is reprogrammed, or if the power is lost. Perfect for datalogging, clock-building, time stamping, timers and alarms, etc. Equipped with PCF8523 RTC - it can run from 3.3V or 5V power & logic!

The Ariel AI Chip, a state-of-the-art integrated circuit designed for high-performance computing applications, incorporates an innovative architecture that leverages radical transistor technology to optimize AI and machine learning tasks. At the heart of this chip lies a quad-core CPU operating at a clock speed of 2GHz, distinguished by its part number CPU-RT-4C-2G. The chip's power management is efficiently handled by a DC power supply, specified as DCPS-5V, ensuring a stable 5V input. Key to its operation are two NPN transistors, identified by part numbers NPN-TRANS-001 and NPN-TRANS-002, which, along with a pair of 1kΩ resistors (RES-1K and RES-1K-002) and a 10µF capacitor (CAP-10UF), form the critical signal processing and conditioning circuitry. This assembly is designed for seamless integration into advanced computing systems, particularly those focused on Flux AI environments, where its performance and efficiency can be fully leveraged. The Ariel AI Chip sets a new benchmark in AI computing, offering unparalleled processing power and efficiency for cutting-edge applications.

This project involves designing a PCB for the lid assembly of an open-source laptop. The design integrates various sensors, including a microphone, camera, and ambient light sensor, ensuring precise alignment with the display glass. It features touch sensors to control LED lighting, spring-loaded contacts for touch-key interaction, and 3D-printed light diffusers for efficient lighting. Additionally, the PCB includes a power management system with status LEDs and a PFC for connecting to the external laptop PCB. The goal is to create a versatile, upgradeable, and user-friendly component for the laptop's lid. Specific parts of the project include 1. Microphone - Audio input capture 2. Ambient Light Sensor Module - Light intensity measurement 3. Camera - Video capture 4. LDO Regulators (3 TLV74 Series) - Voltage regulation for different components 5. Crystal - Clock generation 6. Touch Sensor Controller - Touch-key interaction 7. Flip-Flop - State keeping in logic circuits 8. LEDs (LTRBR37G Series) - Lighting indication 9. FPC Connector - Interface with main laptop PCB

The Ariel AI chip prototype, designed for integration with Flux AI for advanced simulation and testing, incorporates a suite of electronic components optimized for high-performance computing applications. At the heart of this system lies a CPU with a radical transistor architecture, featuring a 4-core configuration and a clock speed of 2GHz, identified by part number CPU-RT-4C-2G. Power management is facilitated through a DC Power Supply, specified as DCPS-5V, ensuring a stable 5V supply to the system. The circuit's dynamic performance is modulated by two NPN transistors, NPN-TRANS-001 and NPN-TRANS-002, which, along with precision resistors RES-1K and RES-1K-002 (both 1kΩ), and a 10μF capacitor (CAP-10UF), form the critical signal processing path leading to the CPU. This configuration is designed to provide an efficient, reliable processing environment for AI computations, with an emphasis on minimizing latency and maximizing throughput. The Ariel AI chip's architecture, combining traditional components with an innovative CPU design, offers a versatile platform for developing advanced AI applications, reflecting a significant step forward in computational technology.

The Ariel AI Chip, a pioneering component in the field of artificial intelligence hardware, integrates advanced features designed to enhance computational efficiency and AI processing capabilities. This chip is distinguished by its utilization of a quad-core CPU with a clock speed of 2GHz, operating on a radical transistor architecture that promises significant improvements in speed and power efficiency. Key components that constitute the Ariel AI Chip include a DC power supply with a 5V output (DCPS-5V), NPN transistors (NPN-TRANS-001 and NPN-TRANS-002) that serve as the fundamental switching elements, precision resistors (RES-1K and RES-1K-002) each with a resistance of 1kΩ, and a capacitor (CAP-10UF) rated at 10μF to stabilize voltage and filter noise. This chip is designed for integration into systems requiring advanced AI capabilities, offering a comprehensive solution for developers looking to leverage machine learning and artificial intelligence in their applications. With its innovative architecture and component selection, the Ariel AI Chip stands out as a versatile and powerful tool for a wide range of AI applications, from embedded systems to more complex computational platforms.

The Ariel AI Chip, an innovative component designed for high-performance computing applications, integrates a sophisticated array of electronic parts to deliver unparalleled processing capabilities. At the heart of this system is a CPU with a radical transistor architecture, featuring a core count of 4 and a clock speed of 2GHz, identified by its part number CPU-RT-4C-2G. Power management within the chip is efficiently handled by a DC Power Supply, rated at 5V, with the part number DCPS-5V, ensuring stable and reliable operation. The chip's signal processing and amplification needs are addressed through the inclusion of two NPN transistors, with part numbers NPN-TRANS-001 and a similar variant, providing the necessary gain and switching capabilities for complex computational tasks. Signal conditioning is further enhanced by a pair of 1kΩ resistors, RES-1K and RES-1K-002, and a 10µF capacitor, CAP-10UF, which work together to filter and stabilize the power supply and signal pathways, ensuring clean and noise-free operation. This integration of components within the Ariel AI Chip offers electrical engineers a robust platform for developing advanced AI systems, combining high processing power with efficient power management and signal integrity, suitable for a wide range of applications in the field of artificial intelligence.

CheckIt is a daily habit tool. When you complete a habit, flip a switch, then an LED lights up. Future work will include wiring the 24pin FPC port to the Pico which causes an e-paper screen to display a message when a switch is flipped. This PCB runs using a Raspberry Pi Pico and has plans to be battery powered similar to a digital alarm clock.

Have you ever wanted to wake up to one of the most energizing scents? Have you ever wanted that cup of energy in your hands before you even slide out of your covers? Well want no further! Introducing the Coffee Waker; The knight of your nightstand, a coffee maker alarm clock with one soul purpose, to quickly and scrumptiously wake you up. This is the Coffee Waker Main board. It contains an ESP32-S3, 16 bit Load Cell ADC, 16 bit MP3 DAC, 120V heater cartridge relay, and 12C wakeup light convector.

Have you ever wanted to wake up to one of the most energizing scents? Have you ever wanted that cup of energy in your hands before you even slide out of your covers? Well want no further! Introducing the Coffee Waker; The knight of your nightstand, a coffee maker alarm clock with one soul purpose, to quickly and scrumptiously wake you up. This is the Coffee Waker Main board. It contains an ESP32-S3, 16 bit Load Cell ADC, 16 bit MP3 DAC, 120V heater cartridge relay, and 12C wakeup light convector.

The Ariel AI chip prototype is an advanced electronic component designed for integration into the Flux AI environment, facilitating simulation and testing of AI applications. This component features a collection of carefully selected parts including a DC power supply (DCPS-5V), NPN transistors (NPN-TRANS-001 and NPN-TRANS-002), resistors (RES-1K and RES-1K-002), a capacitor (CAP-10UF), and a cutting-edge CPU (CPU-RT-4C-2G) with a 4-core architecture, operating at a clock speed of 2GHz. The CPU's innovative radical transistor architecture is specifically tailored for high-performance computing tasks associated with AI and machine learning applications. This configuration ensures efficient power management, signal processing, and data flow within the chip, making it an ideal choice for developers and engineers looking to push the boundaries of AI technology. The inclusion of standard components like NPN transistors, resistors, and capacitors, alongside the specialized CPU, allows for a versatile and robust design, suitable for a wide range of AI applications.

The Ariel AI chip prototype is an advanced electronic component designed to enhance the capabilities of Flux AI systems through a sophisticated arrangement of transistors, resistors, capacitors, and a cutting-edge CPU. Key components include two NPN transistors (part numbers NPN-TRANS-001 and NPN-TRANS-002), which are essential for signal amplification, alongside precision resistors (RES-1K and RES-1K-002) each with a resistance of 1kΩ, and a capacitor (CAP-10UF) with a capacitance of 10μF, crucial for filtering and stabilizing the voltage supply. At the heart of the design is a revolutionary CPU (part number CPU-RT-4C-2G) featuring a quad-core setup with a clock speed of 2GHz, based on a radical transistor architecture, designed to deliver unparalleled computational performance for AI tasks. This component set is powered by a 5V DC power supply (DCPS-5V), ensuring a stable and efficient operation. The Ariel AI chip is engineered for high-speed, reliable performance in demanding AI applications, representing a significant advancement in electronic component design for artificial intelligence systems.

The TUSB8041 by Texas Instruments is a highly integrated four-port USB 3.0 hub controller designed to facilitate high-speed data transfers and power management in computer systems, docking stations, monitors, and set-top boxes. This component offers simultaneous SuperSpeed USB (5 Gbps), high-speed (480 Mbps), full-speed (12 Mbps), and low-speed (1.5 Mbps) data connections, ensuring backward compatibility with USB 2.0 and USB 1.x devices. Key features include multi-transaction translation with four transaction translators, asynchronous endpoint buffers for improved data management, and comprehensive battery charging support compliant with various standards including CDP, DCP, and Chinese Telecommunications Industry Standard YD/T 1591-2009. Flexible power management options are available, catering to both per-port and ganged power control configurations, alongside over-current protection mechanisms. The device also supports custom configurations via OTP ROM, serial EEPROM, or I2C/SMBus interfaces, enabling customization for vendor IDs, product IDs, port specifics, and string descriptors. Ease of integration is further enhanced with the ability for on-board and in-system OTP/EEPROM programming via the USB 2.0 upstream port, and the device requires no special drivers, operating seamlessly with any OS that supports USB. Packaged in a compact 64-pin QFN format, the TUSB8041 is offered in both commercial (0℃ to 70℃) and industrial temperature (-40℃ to 85℃) ranges, ensuring robust performance across diverse environmental conditions. With a single clock input requirement and comprehensive system resource support, the TUSB8041 is ideal for developers aiming to implement high-performance and reliable USB hubs in their designs.

The Ariel AI Chip, a pioneering component in the realm of artificial intelligence hardware, integrates a suite of electronic elements tailored for high-performance computing applications. At the heart of this assembly lies a CPU with a Radical Transistor architecture, featuring a quad-core setup clocked at 2GHz, identified by the part number CPU-RT-4C-2G. Power management is facilitated through a DC Power Supply, marked DCPS-5V, ensuring a stable 5V supply to the intricate circuitry. The chip's switching capabilities are bolstered by two NPN transistors, NPN-TRANS-001 and NPN-TRANS-002, which play a crucial role in signal modulation. Essential to the chip's operation are the passive components: two 1kΩ resistors (RES-1K and RES-1K-002) and a 10µF capacitor (CAP-10UF), which together with the transistors, form a robust network ensuring reliable performance under varying load conditions. Designed for integration into advanced AI systems, this chip stands out for its innovative use of standard components in a configuration that emphasizes efficiency, reliability, and high-speed data processing capabilities.

Seeed Studio XIAO ESP32C6 is powered by the highly-integrated ESP32-C6 SoC, built on two 32-bit RISC-V processors, with a high-performance (HP) processor with running up to 160 MHz, and a low-power (LP) 32-bit RISC-V processor, which can be clocked up to 20 MHz. There are 512KB SRAM and 4 MB Flash on the chip, allowing for more programming space, and binging more possibilities to the IoT control scenarios.

This is a seven-segment alarm clock that is controlled by STM32 and can be configured through the buttons on the board #stm32 #alarm #arm #iot

A binary LED clock. Uses the 12 hour system and displays using on/off of LEDS to represent 1/0 of binary. The clock does not automatically set itself and requires the use of three button at the top to set it. Its powered by a 5v power supply.

DIY gesture controlled Arduino Talking Clock. Speech clock that is activated by an infrared distance sensor. When we move our hand in front of sensor, the clock tells the exact time at that moment with a synthesized "robotic" voice.

An analog ASIC designed to clock nonlinear arena ops.

Project featuring stopwatch based on Arduino nano and DYI 7 segment clock with max7219 and ULN2803A transistor array. For comunication project uses nRF24L01. #Arduino #Nano #Shield #project #nRF24 #max7219 #ULN2803A #Stopwatch #Firefighting_sport

A 1 Hz clock signal generator. Simulation testing not done.

this is an old pcb desig for a cheap chess clock,

Nixie tube clock

Welcome to your new project. Imagine what you can build here.

Welcome to your new project. Imagine what you can build here.

Welcome to your new project. Imagine what you can build here.

Template for Arduino Uno R3 Shield. Include an official pinout so you will always know Arduino names, the alternative roles of pins, which one is SDA, or SCL, etc. On PCB you can find the 3D model of the Arduino Uno R3 itself along with the board outline on the silkscreen. #Arduino #Uno #Shield #Template #project-template #project

Welcome to your new project. Imagine what you can build here.

Welcome to your new project. Imagine what you can build here.

Welcome to your new project. Imagine what you can build here.

Welcome to your new project. Imagine what you can build here.

Have you ever wanted to wake up to one of the most energizing scents? Have you ever wanted that cup of energy in your hands before you even slide out of your covers? Well want no further! Introducing the Coffee Waker; The knight of your nightstand, a coffee maker alarm clock with one soul purpose, to quickly and scrumptiously wake you up. This is the Coffee Waker Main board. It contains an ESP32-S3, 16 bit Load Cell ADC, 16 bit MP3 DAC, 120V heater cartridge relay, and 12C wakeup light convector.

555 IC Turned Into A Clock Circuit. ( Astable )

A Race Clock

The Coffee Waker is a unique, full-featured coffee maker alarm clock designed to brighten your morning routine with the irresistible aroma of freshly brewed coffee. By seamlessly integrating multiple high-performance components onto a single main board, the Coffee Waker delivers both functionality and innovation: - **Processing & Connectivity:** Powered by an ESP32-S3, it offers built-in WiFi and Bluetooth, enabling smart scheduling, remote control, and over-the-air updates. - **Precision Sensing:** A 16-bit load cell ADC provides accurate measurements, ensuring precise weight sensing for coffee bean dosing or liquid volume monitoring. - **Quality Audio Output:** The onboard 16-bit MP3 DAC guarantees clear audio playback, from alarm sounds to any custom wake-up messages you program. - **Robust Power Handling:** With a 120V heater cartridge relay and a 12V wakeup light converter integrated, the board safely manages high voltage switching and provides a visually soothing light routine. - **Thoughtful Integration:** Designed with automotive-grade components, precision regulators, and careful signal routing, the Coffee Waker Main Board combines performance with reliability while keeping a compact footprint. Overall, the Coffee Waker transcends the ordinary alarm clock, merging daily utility with modern connectivity and a touch of luxury—making it the perfect addition to any nightstand. #CoffeeWaker #SmartHome #CoffeeMaker #AlarmClock #MorningRoutine #Technology #Innovation

Have you ever wanted to wake up to one of the most energizing scents? Have you ever wanted that cup of energy in your hands before you even slide out of your covers? Well want no further! Introducing the Coffee Waker; The knight of your nightstand, a coffee maker alarm clock with one soul purpose, to quickly and scrumptiously wake you up. This is the Coffee Waker Main board. It contains an ESP32-S3, 16 bit Load Cell ADC, 16 bit MP3 DAC, 120V heater cartridge relay, and 12C wakeup light convector.

Have you ever wanted to wake up to one of the most energizing scents? Have you ever wanted that cup of energy in your hands before you even slide out of your covers? Well want no further! Introducing the Coffee Waker; The knight of your nightstand, a coffee maker alarm clock with one soul purpose, to quickly and scrumptiously wake you up. This is the Coffee Waker Main board. It contains an ESP32-S3, 16 bit Load Cell ADC, 16 bit MP3 DAC, 120V heater cartridge relay, and 12C wakeup light convector.

## PROJECT OVERVIEW Design a compact, battery-powered, IoT-connected plant monitoring PCB sensor node. The board combines WiFi/BLE connectivity, multi-sensor I2C acquisition, LiPo battery management with USB-C charging, and partially weatherproof design for outdoor/planter use. The physical form factor is a FORK (forcina) shape: a wider rectangular head section (~32×30mm) housing all the electronics, and two narrow prongs (~10×45mm each, 8mm gap between them) extending downward to form the capacitive soil moisture electrodes. Reference: the shape resembles a plant stake that is pushed into soil. I trust Flux AI's routing and placement judgment. Please apply your full expertise. The guidance below defines constraints — treat them as requirements, not suggestions. --- ## BOARD SPECIFICATIONS - Layers: 2 (Top + Bottom copper) - Dimensions: Head 32×30mm + two prongs 10×45mm (total board ~32×75mm) - PCB thickness: 1.6mm FR4 - Surface finish: ENIG (Electroless Nickel Immersion Gold) — MANDATORY Reason: the soil prong traces must be gold-plated for corrosion resistance - Min trace width: 0.15mm signal, 0.5mm power - Min clearance: 0.15mm - Soldermask: GREEN on both sides Exception: NO soldermask on the interdigital soil electrode traces on the prongs (the copper must be fully exposed to contact the soil) - Via: min hole 0.3mm, pad 0.6mm - 4× M2.5 mounting holes (2.7mm drill, 5mm annular copper ring) at corners of head section - Conformal coating keep-out zones: SHT40-AD1F-R2 (U8), VEML7700 (U2), soil electrode traces on prongs, USB-C connector J1 --- ## COMPLETE BILL OF MATERIALS ### Active ICs **U1 — ESP32-C3-MINI-1** (Espressif, LCSC C2838502) - Main microcontroller: RISC-V 32-bit 160MHz, 4MB flash, 400KB RAM - WiFi 802.11b/g/n 2.4GHz + BLE 5.0 - Package: SMD module 13.2×16.6×2.4mm, castellated edges - Operating voltage: 3.0–3.6V from VCC rail - I2C: SDA=GPIO8, SCL=GPIO9 - USB: D+=IO19, D-=IO18 - Status outputs: CHG_STATUS=IO2, PG_STATUS=IO3, LOAD_EN=IO4 - CRITICAL placement: antenna area (rightmost ~3mm of module) must hang over board edge OR have copper keepout zone (no copper top or bottom under antenna area). This is mandatory for RF performance. - Add 100nF + 10µF decoupling on 3V3 pin, placed within 1mm of pin **U2 — VEML7700-TT** (Vishay, LCSC C78606) - Ambient light sensor, 0.0036–120,000 lux, I2C address 0x10 - Package: ODFN-6, 2.0×2.0×0.5mm - Operating voltage: 2.5–3.6V - Current: 90µA active, 0.2µA power-down - CRITICAL placement: position at TOP EDGE of head section, centered horizontally. The sensor photodiode window (top of package) must face upward toward the case lid. A transparent PMMA optical window (Ø10mm) in the case will be positioned directly above this IC. Leave 0mm clearance to board edge on that side if possible. The VEML7700 has ±45° field of view, so alignment does not need to be perfect, but centering under the window opening is preferred. - Add 100nF decoupling on VDD, placed within 1mm **U3 — SHT40-AD1B** (Sensirion, LCSC C1550099) — INTERNAL sensor - Temperature + relative humidity sensor, I2C address 0x44 - Package: DFN-4, 1.5×1.5×0.5mm — extremely small, requires careful pad design - Operating voltage: 1.8–3.6V - Current: 3.2µA per measurement (1ms active), 0.1µA sleep - PURPOSE: measures temperature and humidity INSIDE the case (ambient reference) - CRITICAL placement: position in CENTER of head section PCB, far from all heat sources. Minimum 8mm distance from BQ24090 (U6) and ME6211 (LDO1). The SHT40 chip surface IS the sensor — the hygroscopic polymer capacitor is on the top face of the IC. It must NOT be covered by conformal coating. However, for the internal sensor (U3), it can be in a slightly ventilated cavity inside the case to measure internal temperature drift compensation. - Add 100nF decoupling on VDD within 1mm **U8 — SHT40-AD1F-R2** (Sensirion, LCSC C5155469) — EXTERNAL sensor - Same electrical specs as U3 (SHT40 family), I2C address 0x44 - Package: DFN-4 with integrated PTFE filter cap for dust/water protection The filter cap allows vapor to reach the sensor while blocking liquid water - PURPOSE: measures EXTERNAL ambient temperature and humidity (outside the case) - CRITICAL placement: position on the SIDE or BOTTOM EDGE of head section. This sensor must be accessible from outside the case through a ventilated chamber (labyrinth vent structure in case design). It must NOT be covered by conformal coating. The sensor's filter cap must face the vent opening direction. Minimum 10mm distance from BQ24090 and LDO thermal zone. - Connected via TCA9548A channel 1 (see below) — NOT directly on main I2C bus **U4 — FDC1004DGST** (Texas Instruments, LCSC C266239) - 4-channel capacitance-to-digital converter, I2C address 0x50 - Package: WSON-8, 2.0×2.0×0.8mm - Operating voltage: 3.3V - Current: 750µA active, 300nA shutdown - PURPOSE: reads capacitance of interdigital PCB traces immersed in soil. The IC itself is NOT the soil sensor — it measures the capacitance of external electrodes. CIN1 and CIN2 connect to the interdigital copper traces on the prong section. - CRITICAL placement: position at BOTTOM of head section, closest to prong entry point. This minimizes trace length to CIN1/CIN2, reducing parasitic capacitance pickup. Keep CIN1 and CIN2 traces short, wide (0.3mm+), shielded by GND guard rings on both sides of each trace. Route CIN1/CIN2 on the SAME layer (Bottom preferred) as the interdigital electrodes to avoid via parasitic capacitance. - SHLD1 and SHLD2 pins connect to GND (guard shield) - Add 100nF decoupling on VDD within 1mm **U5 — TCA9548A** (Texas Instruments, LCSC C130026) — NEW COMPONENT vs previous schema - 8-channel I2C multiplexer, I2C address 0x70 - Package: SOIC-24 or TSSOP-24, select smallest available footprint - Operating voltage: 1.65–5.5V - PURPOSE: MANDATORY to resolve I2C address conflict between U3 and U8, both of which have fixed address 0x44. Without this IC the two SHT40 sensors will collide on the bus and produce corrupt readings. Channel 0: connects to U3 (SHT40 internal) Channel 1: connects to U8 (SHT40 external) Main I2C bus (from ESP32): connects to TCA9548A upstream SDA/SCL - Add 100nF decoupling on VCC within 1mm - Reset pin (active low): connect to VCC via 10kΩ (always enabled) OR connect to a GPIO for software reset capability **U6 — BQ24090DGQT** (Texas Instruments, LCSC C179663) - Single-cell LiPo/Li-ion battery charger, input 4.5–6.5V, charge voltage 4.2V - Package: DSBGA-9 (wafer-level), extremely small ~1.6×1.6mm - CRITICAL THERMAL: this IC dissipates up to 0.5W during charging. Place a copper thermal pad area ≥1cm² on BOTH layers under the IC. Add minimum 4 thermal vias (0.3mm hole, 0.6mm pad) under thermal exposed pad. Keep this IC at MAXIMUM distance from both SHT40 sensors. Thermal isolation: route at least 10mm of thin trace (~0.2mm) between BQ24090 thermal zone and any temperature-sensitive component. - ISET pin: connect to R3 (1.8kΩ) to set Icharge ≈ 494mA (C/4 for 2000mAh) - PRETERM pin: connect to R2 (5.1kΩ — keep existing value, sets termination threshold) - ISET2 pin: connect per datasheet recommendation (typically VSYS or VBAT) - TS pin: connect to R4 (10kΩ NTC thermistor or static resistor to GND) If using static resistor: 10kΩ to GND disables thermal protection RECOMMENDATION: add NTC 10kΩ B=3950 near battery for thermal protection - CHG# (open drain): connect to LED_RED via 330Ω to VCC, and to U1 IO2 via 10kΩ - PG# (open drain): connect to LED_GREEN via 330Ω to VCC, and to U1 IO3 via 10kΩ - OUT pin: VBAT rail (to battery positive and to LDO input) **LDO1 — ME6211C33M5G-N** (Nanjing Micro One, LCSC C82942) - LDO regulator, Vin 2.0–6.0V → Vout 3.3V fixed - Package: SOT-23-5, 2.9×1.6mm - Quiescent current: 55µA (higher than MCP1700, but adequate) - Dropout: 300mV @ 100mA - CE pin: connect to VCC (always enabled) or to ESP32 GPIO for power gating - THERMAL NOTE: at full system load (~100mA), dissipation = (Vbat-3.3)×0.1 ≈ 40–90mW. Low risk, but keep minimum 5mm from SHT40 sensors. - Vin decoupling: C2 1µF + C1 100nF - Vout decoupling: C3 10µF (electrolytic or ceramic) + additional 100nF ceramic **O1 — SI2301CDS** (Vishay, LCSC C10487) - P-channel MOSFET, Vds=-20V, Id=-3A, Vgs(th)=-0.4V typ - Package: SOT-23, 2.9×1.6mm - PURPOSE: load switch between VBAT and LDO1 input, controlled by ESP32 This allows the ESP32 to cut power to all sensors during deep sleep for maximum battery life (if desired — optional feature) - Gate connection: 10kΩ pull-up resistor from Gate to VBAT (MOSFET OFF by default) + GPIO IO4 from ESP32 drives Gate to GND through 1kΩ series resistor to turn ON IMPORTANT: this was missing from previous schema — gate must NOT float. Series 1kΩ on gate limits gate charge current and protects GPIO. Pull-up 10kΩ to VBAT ensures MOSFET stays OFF during ESP32 boot/reset. - Source: VBAT (battery positive) - Drain: LDO1 VIN ### Connectors and Passive Components **J1 — USBC_C165948** (USB Type-C SMD receptacle, LCSC C165948) - USB-C connector for 5V power input and ESP32 programming - Position: TOP EDGE of head section (accessible when device is in soil) - VBUS pins → BQ24090 IN (via R_protection 1Ω/1A fuse resistor optional) - D+ → ESP32 IO19, D- → ESP32 IO18 - GND → GND plane - All CC pins → GND via 5.1kΩ resistors (CC1: R_CC1 5.1kΩ, CC2: R_CC2 5.1kΩ) These are MANDATORY for USB-C to deliver 5V (tells charger it is a sink device) WITHOUT these resistors the USB-C port will NOT receive power from modern chargers. **U_BAT — LiPo 2000mAh connector** - Use JST PH 2.0mm 2-pin connector (standard LiPo connector) - Position: head section, easily accessible for battery replacement - Polarity protection: the SI2301 load switch also provides polarity protection if wired with Source=Drain correctly (P-FET body diode blocks reverse current) **R1 — 4.7kΩ ±1% 0402** (CHANGED from 5.1kΩ in previous schema) - I2C SDA pull-up: connects VCC to SDA bus - Reason for change: 4.7kΩ is the standard I2C pull-up value per NXP I2C spec. 5.1kΩ causes slower rise times at 400kHz fast-mode, risking data errors. **R2 — 4.7kΩ ±1% 0402** (CHANGED from 5.1kΩ in previous schema) - I2C SCL pull-up: connects VCC to SCL bus **R3 — 1.8kΩ ±1% 0402** - BQ24090 ISET: sets charge current to ~494mA (Ichg = 890/R3) **R4 — 10kΩ 0402** - BQ24090 TS pin bias or NTC resistor (see BQ24090 notes above) **R5, R6 — 5.1kΩ 0402** (NEW — not in previous schema) - USB-C CC1 and CC2 pull-down resistors (MANDATORY for USB-C power delivery) **R7 — 10kΩ 0402** (NEW) - SI2301 Gate pull-up to VBAT **R8 — 1kΩ 0402** (NEW) - SI2301 Gate series resistor from ESP32 GPIO IO4 **R9, R10 — 330Ω 0402** (NEW) - Current limiting for LED_RED and LED_GREEN (status LEDs) **C1 — 100nF 0402 X5R** — LDO Vin decoupling **C2 — 1µF 0402 X5R** — LDO Vin bulk **C3 — 10µF 0805 X5R** — LDO Vout bulk **C4 — 100nF 0402** — ESP32 VCC decoupling **C5–C9 — 100nF 0402** — Per-IC VCC decoupling (one per U2/U3/U4/U5/U8) **C10 — 4.7µF 0402** — BQ24090 IN bypass **C11 — 4.7µF 0402** — BQ24090 OUT bypass **LED1 — Green 0402** — USB power good / charging complete indicator **LED2 — Red 0402** — Charging in progress indicator **BTN1 — 3×3mm SMD tactile switch** (optional, recommended) - Connected between ESP32 EN pin and GND, with 100nF debounce cap - Allows manual reset without USB for field use --- ## ELECTRICAL NETS SUMMARY | Net Name | Description | Connected to | |----------|-------------|--------------| | VBUS_5V | USB-C 5V input | J1 VBUS, BQ24090 IN | | VBAT | Battery voltage 3.2–4.2V | U_BAT+, BQ24090 OUT, O1 Source | | VCC | Regulated 3.3V | LDO1 OUT, all IC VDD/VCC pins | | GND | Common ground | All GND pins, copper pour both layers | | SDA | I2C data (main bus) | ESP32 IO8, TCA9548A SDA_A, VEML7700 SDA, FDC1004 SDA, R1 pull-up | | SCL | I2C clock (main bus) | ESP32 IO9, TCA9548A SCL_A, VEML7700 SCL, FDC1004 SCL, R2 pull-up | | SDA_CH0 | I2C mux channel 0 | TCA9548A SD0, SHT40-internal SDA | | SCL_CH0 | I2C mux channel 0 | TCA9548A SC0, SHT40-internal SCL | | SDA_CH1 | I2C mux channel 1 | TCA9548A SD1, SHT40-external SDA | | SCL_CH1 | I2C mux channel 1 | TCA9548A SC1, SHT40-external SCL | | SOIL_A | Soil electrode set A | FDC1004 CIN1, interdigital traces prong (even fingers) | | SOIL_B | Soil electrode set B | FDC1004 CIN2, interdigital traces prong (odd fingers) | | USB_DP | USB D+ | J1 D+, ESP32 IO19 | | USB_DM | USB D- | J1 D-, ESP32 IO18 | | CHG_STATUS | Charger status | BQ24090 CHG#, LED_RED, ESP32 IO2 | | PG_STATUS | Power good | BQ24090 PG#, LED_GREEN, ESP32 IO3 | | LOAD_EN | Load switch control | ESP32 IO4 via R8, SI2301 Gate | --- ## PARASITIC AND SIGNAL INTEGRITY CONSTRAINTS Please consider the following parasitic effects when placing components and routing: **I2C bus parasitics:** The I2C specification allows maximum 400pF total bus capacitance. With 4 devices on the main bus (ESP32, VEML7700, FDC1004, TCA9548A) plus the multiplexed sub-buses, keep total SDA/SCL trace length under 50mm. Route SDA and SCL as a parallel differential pair with 0.15mm clearance between them. Do not route I2C traces near switching power lines or under the antenna keep-out zone. **FDC1004 CIN1/CIN2 parasitic capacitance — CRITICAL:** Any stray capacitance on CIN1/CIN2 traces directly offsets the soil measurement. Each picofarad of parasitic capacitance reduces measurement range. Requirements: - Keep CIN1/CIN2 trace length under 15mm from FDC1004 pins to prong entry point - Route on Bottom layer only, no layer changes (vias add ~0.5pF each) - Add copper guard ring (connected to SHLD1/SHLD2=GND) completely surrounding each CIN trace on the same layer — this shields the trace from external fields - Maintain 0.5mm spacing between CIN1 trace and CIN2 trace (and their guard rings) - The interdigital soil electrodes on the prongs: finger width 0.8mm, gap 0.8mm, finger length 25mm, approximately 15–20 alternating fingers per electrode These traces have NO soldermask (fully exposed copper, ENIG finish) **BQ24090 switching node:** The BQ24090 is a linear charger, NOT a switching regulator, so there is no switching noise. However, it dissipates power as heat. The primary constraint is thermal, not EMI. Keep input/output bypass capacitors (C10, C11) within 2mm. **ESP32-C3 antenna zone:** Mandatory keepout: no copper, no traces, no vias, no components in the area directly beneath and 3mm around the ESP32 module antenna. The antenna is on the left side of the module. Orient the module so the antenna faces toward the top or side edge of the board. **Power supply decoupling placement:** All 100nF decoupling capacitors MUST be placed within 1mm of their associated VCC/VDD pin. The parasitic inductance of a longer connection nullifies the effect. Place decoupling on the same layer as the IC where possible. The 10µF bulk cap (C3) can be up to 5mm from the LDO output. **Thermal gradients and temperature sensor placement:** The two SHT40 sensors measure temperature via an on-chip bandgap reference. Self-heating of nearby components creates a thermal offset error. Known heat sources on this board and their typical power dissipation: - BQ24090: up to 500mW during USB charging - ME6211 LDO: 40–90mW at typical load - ESP32-C3: 15–25mW in active mode (WiFi), 0.02mW in deep sleep Required minimum distances from any SHT40: - From BQ24090: ≥12mm (critical) - From ME6211 LDO: ≥8mm - From ESP32-C3: ≥5mm (less critical — low dissipation) --- ## THERMAL MANAGEMENT REQUIREMENTS The device will be used outdoors in ambient temperatures from -10°C to +50°C. The case is a sealed or semi-sealed plastic enclosure approximately 35×35×80mm. Internal temperature rise above ambient must be kept below +8°C during USB charging. **BQ24090 thermal design:** - Thermal pad (exposed pad on DSBGA package): connect to copper area on both layers - Top layer: copper fill area ≥ 1cm² directly under and around IC - Bottom layer: mirrored copper fill area ≥ 1cm² connected via thermal vias - Minimum 4 thermal vias under pad: 0.3mm drill, 0.6mm pad, evenly distributed - These thermal vias conduct heat to bottom layer copper which acts as a heatsink - In the case design (outside scope of PCB): a thermally conductive pad between the PCB bottom copper and the plastic case back wall improves heat transfer **ME6211 LDO thermal design:** - Low dissipation at typical 50–80mA load: (4.0V - 3.3V) × 0.075A ≈ 52mW - This is well within SOT-23 package limits (max ~300mW at 25°C ambient) - Standard copper pour around package is sufficient - No additional thermal vias required unless load consistently exceeds 150mA **Fire safety note:** At no point should any trace carry more than its rated current. Power traces (VBAT, VCC) should be minimum 0.5mm for up to 500mA. The USB VBUS trace from J1 to BQ24090 carries up to 500mA — use 0.8mm trace. Add a polyfuse (PTC resettable fuse) 500mA on VBUS line between J1 and BQ24090 for short-circuit protection (LCSC C178886, 0805 package). --- ## WEATHERPROOFING DESIGN GUIDANCE (for PCB layout decisions) The board will be coated with conformal coating after assembly, EXCEPT: 1. SHT40-AD1F-R2 (U8 external sensor) — the PTFE filter cap must remain uncoated 2. VEML7700 (U2) — photodiode window must remain uncoated and unobstructed 3. Interdigital soil traces on prongs — must remain bare copper (ENIG) for soil contact 4. USB-C connector J1 — coating would block the port 5. Battery JST connector — coating would block connector mating For the PCB layout, implement the following to support weatherproofing: - Place U8 (SHT40 external) and U2 (VEML7700) in designated "coating exclusion zones" clearly marked on the silkscreen layer with dashed boundary lines - Add silkscreen labels: "NO COAT" next to U8 and U2 - Add silkscreen label: "EXPOSED — SOIL ELECTRODES" on the prong traces - The board outline on the prong section must have no sharp corners — use R1mm rounded corners where prongs meet the head section to prevent cracking when the device is pushed into soil --- ## INTERDIGITAL SOIL ELECTRODE SPECIFICATION (prong section) The bottom two prongs of the board ARE the soil moisture sensor. Trace parameters for the interdigital (comb/fork) capacitive electrodes: - Layer: Bottom copper - Trace width: 0.8mm - Gap between adjacent fingers: 0.8mm - Number of fingers per electrode: 16 (8 connected to CIN1, 8 to CIN2, alternating) - Finger length: 25mm - Connection point: at the top of the prongs where they join the head section - Guard ring: GND copper guard ring around the entire interdigital pattern on Bottom layer - NO soldermask over any part of the interdigital pattern - The two electrodes (SOIL_A and SOIL_B) must be symmetrically distributed so that a uniform electric field forms between them when immersed in soil - Add stitching GND vias around the prong perimeter every 8mm --- ## SILKSCREEN AND REFERENCE DESIGNATORS All components must have visible reference designators on the silkscreen layer. Minimum text size 0.6mm height. Add the following board information: - Top left: "SmartPlant v1.0" - Top right: "riccardo.schiavo.1" - Date code placeholder: "DATE: ______" - Near J1: PIN 1 marker and "USB-C POWER + FLASH" - Near U8: "EXTERNAL SENSOR — NO COAT" - Near prong junction: "SOIL ELECTRODES — NO MASK — ENIG" - Near ESP32 antenna area: keepout boundary marker --- ## I2C DEVICE MAP (for firmware reference) | Address | Device | Bus | Notes | |---------|--------|-----|-------| | 0x10 | VEML7700 (U2) | Main I2C | Direct connection | | 0x50 | FDC1004 (U4) | Main I2C | Direct connection | | 0x70 | TCA9548A (U5) | Main I2C | I2C multiplexer | | 0x44 ch.0 | SHT40 internal (U3) | TCA9548A channel 0 | Via mux | | 0x44 ch.1 | SHT40 external (U8) | TCA9548A channel 1 | Via mux | --- ## FINAL NOTES FOR FLUX AI I trust Flux AI's judgment on: - Exact component placement optimization within the constraints above - Via placement and layer assignments for non-critical signals - Polygon fill strategy and via stitching density - Any minor trace re-routing needed to clear DRC errors - Silkscreen label exact positioning to avoid overlap with pads Please prioritize in this order: 1. Electrical correctness (no DRC errors, no antenna violations) 2. Thermal management (BQ24090 copper, SHT40 distance from heat) 3. Signal integrity (FDC1004 CIN guard rings, I2C trace length) 4. Manufacturability (SMT assembly friendly, no isolated pads, no acute angles) 5. Physical compactness within the fork shape outline Generate a complete 2-layer PCB ready for Gerber export to PCBWay.

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