PCB Design for ESP32 Automation of 30A relays

Designing a 30A ESP32 Home Automation Circuit using KiCAD 🏠

OVERVIEW:

The goal was to create a safe, reliable, and high-current circuit for IoT-based home automation. Along the way, I learned not just about schematic capture and PCB design, but also about practical layout techniques that matter when handling significant current.
3D view of the PCB design made in KiCAD highlighting my labelling and component placements.

FINDINGS:

With the advent of IoT, there is a market for the control of multiple electrical items at home. This project is made with that intention in mind. ESP32 is the central microcontroller with Wi-Fi/ Bluetooth connectivity ideal these types of applications. It will govern the needed current to flick the relay poles from chosen relay/octocoupler components. In detail, the following analog/digital components are highlighted the functionality and safety of the board made:

  • Relays (K1: RAYEX-L90AS, K2: PR13-5V-450-1C)
    • These handle 30A / mains-level switching, isolating high voltage from the low-voltage ESP32 domain.
  • Optocouplers (U2, U3: PC817)
    • Provide electrical isolation between ESP32 GPIO signals and relay driver circuits.
    • Prevents voltage spikes or surges on the relay side from damaging the ESP32.
    • Critical safety feature separating low-voltage control logic (ESP32) from high-voltage relay switching.
  • Transistors (Q1, Q2: S8050 NPN BJTs)
    • Act as drivers to energize the relay coils, since ESP32 GPIO pins cannot supply enough current directly.
  • Flyback Protection with Diodes (D2, D3: 1N4148)
    • Likely used as flyback diodes across relay coils.
    • Protects transistors and ESP32 from voltage spikes caused by coil inductance when the relay is turned off.
  • Status Indication with LEDs (D1, D4)
    • Provide visual feedback when relays or control signals are active.
  • Stable Power Regulation
    • AMS1117-3.3 (U4) → provides a regulated 3.3V supply for ESP32.
    • HLK-PM01 (PS1) → an isolated AC-DC converter (230V AC → 5V DC), ensures compact, safe, and isolated power supply for the whole system.
  • Push Buttons (SW1, SW2)
    • Allow manual override or testing of the circuit, which is also important in safety-critical systems.

LEARNINGS:

This project comes with its own setbacks and deviation from the schematic source in which I was basing it from, hence, I’m proud that with my own tracing and decisions created this unique PCB design. The learnings that I was able to get from this project is the following:

Using Vias Effectively

  • Vias are critical when routing signals between PCB layers.
  • For high-current traces, multiple vias in parallel reduce resistance and improve thermal performance.
  • This reinforced the idea that vias aren’t just “signal tunnels” — they’re part of the current-carrying capacity of the design.

Copper Zones & Ground Planes

  • I applied copper pour zones to handle higher current paths and improve grounding.
  • I was able to tackle electrical signal discharge (ESDs) using this feature as it minimizes voltage drops and reduces EMI in sensitive circuits.
  • It also makes soldering easier since larger copper areas can help with thermal dissipation.

_Replacing & Updating CAD Components | Troubleshooting

  • Some of the initial footprints and 3D models were missing or broken.
  • I learned to replace them with updated library components and assign correct 3D models.
  • This improved not just the functional accuracy of the PCB but also gave me a realistic 3D preview of the board — crucial for verifying clearances in enclosures. Kindly check the images below pertaining to this!!
Images that highlight replacement of outdated 3D components for PCB design and finding the replacement through GrabCAD :))

Overall, I was able to do the following:

Schematic Capture

  • Placed the ESP32, relays, connectors, and supporting components.
  • Double-checked footprints for high-current parts.
Schematic made for this project. This was captured in essence from the source with adjustments on labelling

PCB Layout

  • Oriented relays and connectors to streamline wiring.
  • Added wide copper traces and copper zones to support 30A current flow.
  • Used vias strategically to distribute current across layers. I may have made some inefficiencies in the routing using this method but overall, the PCB design should be functional
PCB layout made for this project and final routing of components that features fill-zone for grounding and ESP32 controller at the bottom.
  1. Final Checks
    • Ran Design Rule Check (DRC) to catch clearance issues.
    • Updated missing 3D models for realistic visualization.
    • Viewed the completed design in the 3D viewer to ensure correct placement and alignment.

This was fun for me since I got to experiment with ESP32 for PCB use and specific functions :>

PS. Whats left of this design is to acutally test it with the physical components but overall, with the checks that I did, it should be ready for production as I also did consider it for manufacturing! EDA and CAD is available upon request.