Our Portfolio

# LoRa Sensor Node — Solar Harvesting and 15 kV Line Sensing --- ## Description A battery-and-solar powered remote monitoring node for electric fence lines. It sits outdoors with no mains power and no network, and must report line condition over long range for years without a site visit. **Stack** - **SX1262** sub-GHz LoRa transceiver - **STM32L052** ultra-low-power microcontroller - **2S LiFePO4** battery pack with **MPPT** solar charging - High-voltage sensing front-end rated for **12–15 kV** line pulses --- ## The Hard Part **15 kV on the same board as a microcontroller.** Electric fence energisers produce high-voltage pulses by design. The sensing front-end has to survive and measure them while the digital side, millimetres away, sees nothing. Isolation, spacing, and clamp strategy set the board outline before any routing. **Power budget over seasons, not hours.** The node has to carry itself through low-light weeks on stored charge. MPPT harvesting, LiFePO4 chemistry for cycle life across an outdoor temperature range, and an STM32L0 chosen for sleep current — the radio duty cycle then has to fit what the harvest actually delivers. **Range with a small antenna.** LoRa buys link budget, but only if the RF section is laid out to keep it. Matching network, ground plane treatment, and antenna keep-out were resolved at layout. --- ## Deliverables - Complete bill of materials with sourcing and lifecycle checked - Schematic and board outline with high-voltage spacing enforced - Power budget model against expected solar yield - Fabrication package --- *Published without client, project name, or location under NDA. Silicon and architecture are unchanged.*

# Class-E RF Generator with a Three-Layer Safety Architecture --- ## Description A high-efficiency RF power generator for a medical application, running **Class-E** switching at **500 kHz**. Class-E is chosen when efficiency matters more than simplicity — the switch turns on at zero voltage, so losses drop sharply, but the topology is unforgiving about component tolerance and timing. **Stack** - **Class-E** switching topology at 500 kHz - **ESP32** using its **MCPWM** peripheral for gate timing - **TC4420** high-current gate driver - Three independent layers of safety supervision --- ## Why Three Layers RF energy delivered to a patient is not a system where a single interlock is acceptable. Any one protection mechanism can fail, and the failure is often silent. The architecture uses three independent layers so that no single fault removes protection: hardware limiting that acts without software, firmware supervision that monitors operating conditions, and a watchdog path that shuts the stage down if the controller stops behaving. Each layer assumes the others may already have failed. That assumption is the design. --- ## Engineering Constraints **Zero-voltage switching depends on timing.** Class-E only stays efficient while switching lands in the correct part of the resonant cycle. Gate timing came from the ESP32 MCPWM peripheral, which gives hardware-accurate edges rather than software-timed ones — deterministic timing is a safety property here, not just a performance one. **Gate drive at 500 kHz.** The TC4420 supplies the current needed to move gate charge fast enough to keep switching losses low. Slow edges at this frequency turn efficiency into heat. **Thermal behaviour is a safety property.** In a Class-E stage, thermal runaway and efficiency loss are the same failure progressing. --- ## Deliverables - Schematic, layout, and fabrication package - Safety architecture documented layer by layer with failure assumptions stated - Firmware for gate timing and supervision - Design review against the intended operating envelope --- *Published without client, project name, or location under NDA. Topology, silicon, and safety architecture are unchanged.*

# DIN-Rail Industrial Carrier Board for a Compute Module --- ## Description A carrier board that turns a commercial compute module into a DIN-rail industrial controller — the board that sits between a Linux-capable module and a factory floor. **Interfaces** - **RS-485** for legacy fieldbus and Modbus devices - **Dual Ethernet** for separated control and plant networks - **24 V digital I/O**, the industrial standard rather than logic levels - **DIN-rail form factor** — the enclosure sets the outline, not the other way round --- ## Engineering Constraints **24 V I/O next to a compute module.** Industrial I/O runs at 24 V and is expected to survive miswiring, inductive kickback, and long cable runs. The compute module is a low-voltage device with no tolerance for any of that. Protection and isolation are the design, not an afterthought. **Two Ethernet ports that stay independent.** Separated networks are only separated if the board keeps them separated — magnetics placement, isolation barriers, and return-path discipline decide whether that holds under noise. **A fixed mechanical envelope.** DIN-rail width is not negotiable. Connector placement, mounting, and thermal path were fixed before component placement began, because in that form factor the mechanics constrain the electronics. --- ## Documented Architecture Issued as a controlled architecture document under its own identifier, covering the interface map, power tree, and I/O allocation. The client owns it and can hand it to another engineer without a conversation. --- ## Deliverables - Hardware architecture document under formal revision control - Schematic, layout, and fabrication package - Interface and I/O allocation map - DFM review before release --- *Published without client, project name, or location under NDA. Architecture and interfaces are unchanged.*

# Buck Converter Damage Traced to a Fixed-Output Part Variant --- ## Description Boards were coming back with damaged buck converters. The schematic was correct, the layout was sound, and the part number on the BOM was the right part — on paper. --- ## The Fault The **AP63203** buck converter ships in more than one variant. One is adjustable and expects an external feedback divider to set the output. Another is **fixed-output**, with the divider already inside the package. The design used an external feedback divider, which is correct — for the adjustable part. The variant actually fitted was the **AP63203WU-7**, the fixed-output version. With an internal divider and an external one both acting on the same node, the regulator was driven outside its intended operating point and damaged itself. The suffix is the entire difference. Everything upstream of it was right. --- ## Why It Matters This is a BOM fault, not a design fault, and it is invisible in every artefact a normal review looks at. The schematic is correct. The layout is correct. The part number is *almost* correct. It only surfaces by reading the ordering-information table against the circuit the part is sitting in — which is a habit, not a tool. --- ## Deliverables - Failure mechanism explained from the datasheet variant table - Corrected part number for the topology in use - BOM audit against variant suffixes across the rest of the design --- *Published without client, project name, or location under NDA. Silicon and findings are unchanged.*

# Three-Phase Smart Energy Meter — Metering IC to Cloud --- ## Description A complete three-phase smart energy meter, taken from hardware architecture through firmware to the cloud backend that receives the data. One vendor across the whole stack, rather than a board handed to a separate firmware team and a separate backend team. **Stack** - **ATM90E36A** three-phase metering front-end — voltage, current, power, energy, and harmonics - **ESP32-S3** application processor - **Quectel EC200U** cellular modem for backhaul where there is no local network - **CC2652P** Zigbee radio for local mesh to neighbouring meters - Server side: MQTT broker, time-series storage, dashboards --- ## Engineering Constraints **Mains-referenced measurement alongside low-voltage digital.** The metering front-end sits on the mains side while the processor and radios do not. Creepage and clearance are layout constraints, not annotations — they set the placement before routing begins. **Two radios on one board.** Cellular and Zigbee share an enclosure and a ground. Antenna placement, keep-outs, and supply decoupling were resolved at layout rather than patched afterwards with shielding. **Accuracy is the product.** A metering board that reads slightly wrong is worse than one that fails outright, because nothing announces the error. Reference and burden component selection were treated as accuracy decisions, not BOM line items. --- ## Documented Architecture The hardware architecture was issued as a controlled document with its own identifier, covering the power tree, GPIO allocation across processor and both radios, and the interface map between metering front-end, processor, and backhaul. The client owns that document. It can be handed to another engineer without a conversation — which is the point of writing it. --- ## Deliverables - Hardware architecture document under formal revision control - Schematic, layout, and fabrication package - GPIO and peripheral allocation map - Firmware through to data reaching the broker - Backend ingestion, storage, and dashboards --- *Published without client, project name, or location under NDA. Silicon and architecture are unchanged.*

# Design Review: Three Ship-Blocking Faults Caught Before Fab --- ## Description A client submitted a completed mixed-signal board for an independent review before releasing it to fabrication. The design combined **stepper motor drive**, **switching power conversion**, **digital isolation**, and an **audio output stage** — four subsystems that each impose different constraints on the same board. The board was considered finished. The review found three separate faults, each of which would have shipped as a field failure. **Reviewed stack** - **DRV8452** stepper motor driver - **TPS54360** wide-input buck converter - **ISO7721** dual-channel digital isolator - **MAX98357** Class-D audio amplifier - **SPH0641** MEMS microphone --- ## Faults Found **1. Switching-frequency resistor miscalculated** The TPS54360 frequency-setting resistor did not produce the intended switching frequency. Left as designed, the converter would have run outside its intended operating point, shifting the noise spectrum into a band the audio stage could not reject and altering thermal behaviour under load. **2. Enable-pin overvoltage** The buck converter enable pin was exposed to a voltage above its absolute maximum rating under a normal input condition — not a fault case. This is the class of error that survives bench testing and fails intermittently in the field, because the damage is cumulative. **3. Digital isolator channel direction reversed** The ISO7721 is a dual-channel isolator with a fixed direction per channel. One channel was wired against its direction of travel, so that signal path would never have functioned. The board would have assembled, powered up, and silently failed on one interface. --- ## Why It Matters None of these faults are exotic. Each one is a single line in a datasheet that was not cross-checked against the schematic — and each one would have cost a full fabrication and assembly cycle to discover. A review is measured against the cost of the respin it prevents, not against its own hours. --- ## Deliverables - Annotated fault list with datasheet references for each finding - Corrected values and pin assignments - Severity ranking: ship-blocking vs. improvement - Review notes formatted for handoff to the original design team --- *Published without client, project name, or location under NDA. Component selection and findings are unchanged.*

# Boot Failure Root-Caused to a SYSBOOT Pin Conflict --- ## Description A network cable tester built around a **Sitara AM4379** application processor would not boot. The board powered up, rails were correct, and there was no visible fault — it simply never started. The client had already spent time on firmware and power before bringing the board in for diagnosis. --- ## The Fault The AM4379 samples a group of **SYSBOOT** pins at reset to decide where to boot from. Those pins are dual-purpose: after reset they become ordinary I/O, so it is easy to assign them a peripheral function during design and never notice the conflict. One of the SYSBOOT lines had been given a second function whose idle state changed the sampled boot value. The processor was reading a boot mode that did not correspond to any device present on the board, so it never began execution. Nothing was broken. The board was doing exactly what it had been told to do. --- ## Why It Was Hard To Find This class of fault presents as a dead board with healthy rails, which sends most debugging toward power and firmware — the two places it is not. The evidence is in the boot-mode strap table in the datasheet, cross-referenced against the idle state of every net attached to those pins. Finding it is a matter of knowing where to look, not of instrumentation. --- ## Deliverables - Root cause identified with the responsible net named - Boot-strap table cross-referenced against the schematic - Rework path for existing hardware, and the schematic fix for the next revision --- *Published without client, project name, or location under NDA. Silicon and findings are unchanged.*

# Industrial Multi-Channel Power Controller Board | Fused Output Distribution | DC/DC Regulated | Version 1 --- ## Description Custom-designed **industrial-grade multi-channel power controller board** engineered for robust DC load management and power distribution in demanding environments. This large-format red solder mask PCB features an extensive array of **fused high-current output channels** (F1–F23+), **dual battery input support** (Batt1+, In Batt2+), and **on-board DC/DC conversion** — delivering reliable, protected power to dozens of downstream loads simultaneously. The board integrates a **microcontroller-based control system** with a dedicated **diagnostic header** for real-time system monitoring, fault detection, and field debugging. Over **40+ individually addressed output connectors** (FH1–FH49) provide flexible wiring to relays, solenoids, actuators, sensors, and other industrial peripherals. Multiple **automotive/industrial-grade blade fuses** protect each output channel against overcurrent and short-circuit faults. ### Inferred Specifications | Parameter | Detail | |---|---| | **Input Voltage** | Dual battery input (estimated 12V–48V DC range) | | **Power Regulation** | On-board DC/DC converter module with IN GND / DC/DC F references | | **Output Channels** | 40+ fused outputs via Molex/JST-style headers (FH1–FH49) | | **Fuse Protection** | Automotive blade fuses (F11, F12, F19–F23 + additional) | | **Controller** | Microcontroller (likely STM32 or similar ARM Cortex-M, QFP package visible) | | **Communication** | Diagnostic port (likely UART/CAN), USB connector, pin headers for I2C/SPI | | **Switching** | On-board relay(s) and/or MOSFET high-side drivers for load control | | **Connectors** | High-current screw/blade terminals (X1–X4), Molex-style multi-pin headers | | **Board Dimensions** | Large form factor (~200mm × 150mm estimated) | | **PCB Layers** | Multi-layer (estimated 4-layer) with heavy copper for power planes | | **Solder Mask** | Red, industrial-grade finish | | **Mounting** | 4-corner mounting holes for DIN-rail or panel enclosure mounting | | **Version** | Version 1 (silkscreen marked) | ### Key Features - **Dual Battery Input** — supports redundant or load-sharing power configurations (Batt1+, In Batt2+) - **40+ Fused Output Channels** — individually protected distribution to FH1–FH49 output headers - **On-Board DC/DC Conversion** — regulated secondary rails for logic, sensors, and low-power peripherals - **Blade Fuse Array** — field-replaceable automotive-style fuses for rapid maintenance - **Diagnostic Interface** — dedicated diagnostic header and USB port for configuration, logging, and fault readout - **Microcontroller Intelligence** — programmable load sequencing, overcurrent monitoring, and fault management - **Heavy-Duty Connectors** — high-current input/output terminals rated for industrial wiring - **Scalable I/O Architecture** — modular header layout supports application-specific wiring harnesses ### Applications - Industrial machinery power distribution & load management - Vehicle / fleet electrical system controllers (trucks, agricultural, marine) - Building automation & HVAC power distribution panels - Renewable energy system load controllers - Telecom & server rack DC power distribution - Factory automation relay & actuator driver boards - Railway & transportation auxiliary power systems - Mining & heavy equipment electrical control units --- > **Designed & Engineered by [Circuit-Board-Design](https://circuit-board-design.com)** — Custom Industrial Electronics, Power Systems & PCB Design

# Custom 24GHz Radar Module | Infineon BGT24 + STM32 Processing | PCB Design & Engineering --- ## Description Custom-designed **24GHz radar sensor module** featuring **Infineon's BGT24-series** radar transceiver IC with **STM32 microcontroller-based** signal processing. This compact circular PCB design integrates the complete RF front-end with dual SMA connectors for TX/RX antenna interfacing, I2C communication (SCL/SDA), V_tune frequency control, and on-board IF signal conditioning (IFI/IFQ). The multi-layer board incorporates careful **RF layout practices** including controlled impedance traces, extensive ground stitching vias, and shielded component placement for optimal 24GHz performance. Key header breakouts provide access to GND, 5V, TX_EN, V_DAC, VCC_DIV, and EN control signals — enabling seamless integration into larger embedded systems. ### Key Features - **Radar IC:** Infineon BGT24-series 24GHz radar transceiver - **Processing:** STM32 microcontroller for DSP and control - **RF Interface:** Dual SMA connectors (TX/RX) - **Communication:** I2C (SCL/SDA), analog IF outputs (IFI/IFQ) - **Control Signals:** TX_EN, EN, V_tune, V_DAC - **Power:** 5V input with on-board regulation (VCC_BGT, VCC_PTAT, VCC_DIV) - **Form Factor:** Compact circular PCB with shielded RF section - **PCB Technology:** Multi-layer, controlled impedance, dense ground via stitching ### Applications - Industrial motion & presence detection - Distance measurement & ranging - Speed detection & traffic monitoring - Gesture recognition & smart home automation - Security & perimeter surveillance - IoT smart sensing systems --- > **Designed & Engineered by [Circuit-Board-Design ](https://circuit-board-design.com)** powerd by [ Electuni LLC](https://electuni.com)**— Custom RF, Embedded Systems & High-Frequency PCB Design

In the fast-paced service industry, efficient queue management and real-time communication are critical. Whether it’s a bustling restaurant, a busy fitness center, or a clinic relying on a token system, the hardware driving these processes needs to be reliable, compact, and highly connected. For this project, I engineered a custom Internet of Things (IoT) hardware solution designed specifically to handle real-time bookings, reservation tracking, and instant notification dispatching. At the heart of this board is the highly efficient ESP32-C3 microcontroller. The Core Objective The goal was to design a versatile, small-form-factor PCB capable of maintaining a persistent internet connection to sync with cloud-based reservation platforms. It needed to be cost-effective for mass deployment while retaining enough processing power to handle secure network protocols and drive external displays or alerts. Hardware Overview & Key Features This custom PCB was designed with both functionality and physical footprint in mind. Key highlights of the board include: ESP32-C3 Module: The brain of the operation. The ESP32-C3 provides robust Wi-Fi and Bluetooth LE 5.0 connectivity. Its RISC-V core is power-efficient yet more than capable of handling real-time WebSocket connections or REST API calls to backend booking servers. Modern USB-C Interface: Included for reliable power delivery, seamless serial programming, and debugging. Flexible Power Management: The board integrates efficient voltage regulation to handle varying input loads, ensuring stable operation during continuous 24/7 uptime. Onboard Status Indicators: Integrated LEDs provide immediate visual feedback for network status, power, and active notification triggers, making on-site troubleshooting straightforward. Expansion Ready: The top pin header (H1) allows for easy interfacing with external peripherals, such as larger token display screens, thermal printers, or audio buzzers for notification alerts. Real-World Applications Because of its flexible design, this board serves as the foundational hardware for multiple service-oriented systems: Restaurant Reservation Systems: The board can act as a bridge between the host's tablet and table-side pagers, or directly control a "Now Serving" display, updating in real-time as tables clear. Gym Access & Booking: Can be integrated into turnstiles or front-desk check-in points to instantly verify class bookings or membership status via Wi-Fi. Digital Token & Queue Management: Perfect for clinics, banks, or government offices. The board fetches the current token number from the database and drives the overhead LED matrix or segmented displays to call the next customer. Conclusion This ESP32-C3 board demonstrates the power of custom embedded engineering to solve specific, real-world business bottlenecks. By moving away from off-the-shelf development boards and designing a purpose-built PCB, the final product is more secure, occupies a fraction of the space, and is optimized perfectly for IoT queue and reservation management. If you are looking to develop custom IoT hardware or need professional PCB design services for your next project, feel free to reach out through the contact page.