PostAlert IoT Wireless Mailbox Notification System

I designed a two-part IoT mailbox notification system consisting of a battery-powered outdoor sensor and an indoor touchscreen base station. The outdoor unit remains in an ultra-low-power sleep mode until mail is detected, then transmits a LoRa message to the indoor unit. The indoor unit displays the delivery date and time on a color touch LCD and connects to the homeowner's WiFi network to send notifications through a mobile app. Both units feature custom PCB antennas that I designed using a Texas Instruments reference design and optimized through NanoVNA measurements and Smith Chart impedance matching.

Technologies: ESP32, WiFi, Bluetooth LE, LoRa, Touch LCD, Low-Power Battery Design, PCB Design, Custom PCB Antennas, NanoVNA, Smith Chart Impedance Matching, Embedded Firmware

Result: Achieved an ultra-low-power sleep current of approximately 500 nA for the outdoor mailbox unit, enabling extended battery life. The custom PCB antennas eliminated the need for external antennas, reducing both component cost and assembly complexity while maintaining reliable wireless performance.

Control Pendant ESD Failure — Root Cause Analysis & Redesign

A large equipment manufacturer had a long‑standing issue with one of their control pendants: the unit would reset or lock up when exposed to electrostatic discharge (ESD). The original design included ESD snubber components, but the discharge path was incorrect — the energy had nowhere safe to go.

After reviewing the assembly, I identified the flaw in the return path and redesigned the internal structure to provide a proper, low‑impedance route for the ESD event. With the corrected discharge path, the pendant passed ESD testing and the field failures stopped.

Result: A reliable, production‑ready design that eliminated ESD‑induced resets and reduced user complaints.

Six‑Layer Mixed‑Signal PCB — First‑Pass Radiated EMI Success

Traditional PCB layout guidance often recommends splitting analog and digital ground planes and tying them together at a single point. A fellow engineer shared a different approach: use a continuous ground plane and let each signal define its own return path. The physics supports this — return currents naturally flow directly beneath their signal traces.

I applied this method to a complex six‑layer board containing ultra‑low‑level analog circuitry, a high‑voltage switching supply, a microcontroller, DRAM, an FPGA, and an LCD interface. When the board went to the EMI lab, the only issue was unrelated to the PCB itself — the LCD panel’s grounding. A strip of copper tape to provide a proper ground reference solved the problem immediately.

Result: The PCB passed radiated EMI on the first attempt. I’ve used this continuous‑ground‑plane technique ever since with consistently excellent results.

Ultra‑Low‑Power Battery Device — 500 nA Standby Current

I designed a battery‑powered device using a lithium primary cell where maximizing battery life was critical. The design also required reverse‑polarity protection without the voltage drop of a series diode.

I selected an ideal‑diode controller with an enable pin and paired it with a mechanical tilt switch. The tilt switch momentarily enabled the ideal diode, powering the microcontroller. Once awake, the microcontroller asserted a GPIO line to keep power on while it completed its task. When finished, it released the line and the system powered down.

Measured standby current was approximately 500 nA, yielding an estimated battery life of about five years in the intended application.

Result: A robust, polarity‑protected design with exceptional battery longevity and no unnecessary quiescent losses.

FPGA‑Based Replacements for Obsolete ICs

A client needed drop‑in replacements for two obsolete integrated circuits: a bit‑slice microprocessor and a burst‑mode DRAM controller. Redesigning the entire system was not an option.

I implemented both devices in FPGAs and designed small PCBs that matched the original IC footprints. These boards soldered directly into the existing system, preserving the required electrical and timing characteristics while providing a modern, maintainable solution.

Result: The client avoided a costly system redesign and gained long‑term supportability for critical legacy hardware.

Robot‑PLC Synchronization — Eliminating Downtime in a Palletizing System

A manufacturing line used a robot to palletize boxes in a pattern requiring eight box positions and two pallet positions. I was responsible for the robot programming, while another engineer handled the PLC logic.

To ensure reliable coordination, I designed a set of robot outputs that explicitly told the PLC which box position and pallet position were active. Instead of using these signals, the PLC logic used a counter to “track” the robot’s sequence.

Within a week of operation, the system repeatedly fell out of sync. Operators had to stop the line, clear the pallet, reset the counters, and restart the process — causing frustration and downtime.

I revised the PLC logic to use the robot’s outputs directly and removed the counter‑based sequencing. This restored deterministic control: the robot became the master, and the PLC became the slave, ensuring the sequence could never drift.

Result: Reliable palletizing, reduced downtime, and a smoother operator experience.

Pinball MPU Board Restoration — Reverse Engineering a Destroyed 1980s Design

Many 1980s pinball machines used a microprocessor‑based MPU board with battery‑backed RAM. The battery was mounted directly on the board, and over decades, leakage from these batteries caused severe corrosion that destroyed traces, vias, and components. Replacement boards were no longer available, and many machines were being scrapped.

Working with a fellow engineer, I reverse‑engineered the original MPU board, preserving the exact physical outline and connector locations so it would drop into existing machines without modification. During the redesign, we improved the watchdog and reset circuitry to make the system more robust than the original.

The result was a fully functional, modernized replacement board that kept hundreds of machines alive.

Result: More than 500 pinball machines were restored to working condition, preventing them from ending up in landfills and preserving a piece of arcade history.

Qi Wireless Charging System for a Sealed Class II Medical Device

A Class II medical device required a rechargeable battery, but the client also needed the enclosure to be completely sealed to prevent cleaning solution ingress. Traditional charge ports were not acceptable due to contamination risk, sterilization requirements, and long‑term reliability concerns.

I designed a complete Qi wireless charging solution consisting of both the sealed medical device and a custom Qi charging base station. The device integrated the receiver coil, power‑management circuitry, and battery protection, while the base station ensured reliable alignment and charging performance suitable for medical environments.

The system delivered safe, consistent wireless power transfer while maintaining full environmental sealing. When taken to the EMI lab, both the device and the charging base passed on the first attempt — no shielding changes, layout modifications, or redesigns required.

Result: A fully sealed, rechargeable Class II medical device and charging base station that met all specifications and passed EMI testing on the first pass.

Aircraft Super-First‑Class Seat BLDC Motor Control & Pressure‑Adaptive Lumbar System

A premium aircraft suite manufacturer needed a control system for their “super first class” suites. The system required smooth, reliable motion using brushless DC (BLDC) motors, along with a lumbar support module that used a compressed‑air bladder to adjust comfort.

Because cabin pressure changes throughout flight, the lumbar system needed to actively monitor cabin pressure and compensate automatically to maintain consistent support for the passenger.

I worked as part of a two‑engineer team: I designed the electronics, including the BLDC motor control PCB, power stage, commutation handling, safety features, and the pressure‑adaptive lumbar control hardware. A firmware engineer developed the embedded software that interfaced with the seat’s master controller and managed the pressure‑regulated lumbar system.

Both assemblies were engineered to meet the stringent electrical, environmental, and regulatory requirements for aircraft seating systems.

Result: A fully compliant BLDC seat‑motion controller and pressure‑adaptive lumbar module that passed all regulatory testing and integrated seamlessly into the aircraft’s first‑class seating system.

Why These Case Studies Matter

Each of these projects demonstrates the same core strengths: deep understanding of electronics, firmware, and system behavior; practical, physics‑based engineering; fast diagnosis and clean solutions; the ability to work across old and new technologies; and a focus on reliability, manufacturability, and long‑term support.

If you’re facing a similar challenge — or you’d like to avoid these kinds of problems in a new design — we can start with a focused conversation and determine the right level of engagement.

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