12/18/2025 - Do some research for components nedded

DAY 1

Electronic

First of all to intall the Home-Assistant OS we'll need a Raspberry Pi 4 Model B - 4GB, to ensure the multiprotocol with all of our connected devices we'll use a SONOFF ZigBee 3.0 USB Dongle Plus. To power our Raspberry we'll need an alimentation of 15W 3A. To finish to flash the OS we need a SD card 64gb is enough.

Component Selection Logic (Why these parts?)

1. Raspberry Pi 4 Model B (4GB RAM)

• Role: Main Server Hub.
• Engineering Decision: While a Pi Zero 2 could run the OS, it lacks the RAM for a robust setup. I chose the Pi 4 (4GB) to run multiple Docker containers simultaneously (Home Assistant, InfluxDB, Grafana) without using Swap memory.
• Performance: The Quad-core CPU allows local compilation of ESPHome firmwares in seconds, ensuring the system remains responsive even during heavy automation tasks.

2. SanDisk Ultra 16GB microSD

• Role: OS Storage.
• Engineering Decision: (Response to feedback): Switched to 16GB to optimize BOM cost.
• Mitigation Strategy: Since 16GB has lower write endurance than larger cards, I will implement software optimizations in Home Assistant:
  1. Limit the Recorder database retention (purge_keep_days: 7).
  2. Exclude noisy sensors from logging to prevent filling the storage. This ensures the 16GB capacity remains sufficient for the long term.

3. SONOFF Zigbee 3.0 Dongle-E

• Role: Zigbee Coordinator.
• Engineering Decision: Selected the "E" version (EFR32MG21 chipset) for its +20dBm output power, ensuring reliable signal coverage through walls without needing extra repeaters. It also supports future "Matter" protocol updates.

4. Official 15W USB-C Power Supply

• Role: Clean Power Source.
• Engineering Decision: Generic phone chargers often drop voltage under load. Using the official 15W supply prevents "Under-voltage" warnings which are the #1 cause of SD card corruption on Raspberry Pi. ### Links (Please note that these websites are French and may not offer international shipping to countries such as the United States. Be sure to find the components on the corresponding websites.) ## Raspberry (65.70€)

https://www.kubii.com/fr/cartes-nano-ordinateurs/2772-raspberry-pi-4-modele-b-4gb-5056561800349.html

Alimentation (9.60€)

https://www.kubii.com/fr/alimentations/2678-1049-alimentation-officielle-153w-usb-c-pour-raspberry-pi-4-400-3272496300002.html#/couleur-blanc/embout_d_alimentation-europeenne_ue

ZigBee Dongle (17.59€)

https://fr.aliexpress.com/item/1005007390388838.html?spm=a2g0o.productlist.0.0.18b30Be50Be5wa&mp=1&pdp_npi=5%40dis%21EUR%21EUR%2019.54%21EUR%2017.59%21%21EUR%2017.24%21%21%21%40211b441e17660905884225558efc3b%2112000041104829474%21ct%21FR%216452468974%21%211%210&_gl=1*flvybi*_gcl_au*MTUyNjI1MTUwMi4xNzY2MDA0MTU4*_ga*MTExNjc2MTgzOS4xNzM1NTAwODA3*_ga_VED1YSGNC7*czE3NjYwODkwNjQkbzIwJGcxJHQxNzY2MDkwNTQ2JGo1MyRsMCRoMA..&gatewayAdapt=glo2fra

SD Card (10.99€)

https://www.amazon.fr/SanDisk-Cards-Extreme-MICROSDXC-Adapter/dp/B09X7C7LL1?crid=3QM5I2V9SF3XX&dib=eyJ2IjoiMSJ9.zaPQ8EJ0BsknvAnId4B8N-SNB5JnnIOkobTtXIeuiOaxSl5-WtFmsfyuvdXwfNxmYNGfq5AsISrmfQ7UO0Az7HsVjvLELVXFP2ZoFNoFDK1AmlbNsvv7N3n5yjdxhqCsBqypHjEFLGQMMMaGgSnl5e2QwFineVhLlPk2kveBWnHW8WkJJoUV3FqW6ILPDIj1oTjm-XxiTEWg3XFFyNywHFJ9i1lgm7z81d_5273APZjwjORftmxUB-TwliaG5_9Y-S6VegK39h9BhWIpTRZyydf8KKFepb-cG4nma7OgQvc.oi_qz_Ve_CmDZ5485-oO1qq64UFh4r0sj29tI_40TrM&dib_tag=se&keywords=carte%2Bsd%2B64%2Bgo&qid=1712496508&sprefix=carte%2Bsd%2B%2Caps%2C101&sr=8-6&linkCode=sl1&tag=abregepartena-21&linkId=e3803117d9c60426ea610c064c7270b1&language=fr_FR&ref_=as_li_ss_tl&th=1

Total (103.88€)

12/22/2025 - Designing the Box

DAY 2

Design

Today, I design a components plate and a box for it. The components plate clips into the box without screws or glue. You'll need some magnets 10*2mm to clip on the back plate, also you'll need M2.5 inserts and M2.5x5 mm screw for securing the Raspberry Pi.

(Style)

On the components plate you can a small place to fit a D1 (ESP8266), in the front of the box there is a small groove for LEDs you can configure the D1 with WLED and make the box looks better.

Images

Box

Back

Inside

Components Plate

12/23/2025 - Clarifying the Project: Home Assistant Server Architecture

Hi, thanks for the feedback.

I wanted to clarify a few things about the hardware. This project is not just a gateway or an intermediary. It is the full Home Assistant Server.

It runs the Operating System, the database, and the heavy Multiprotocol firmware for the Zigbee dongle. A Nordic chip or a Raspberry Pi 3 would be too weak for this workload, which is why the Raspberry Pi 4 (4GB) is necessary.

Also, the D1 Mini inside is used specifically to control the LEDs with WLED, so it doesn't slow down the main server.

I hope this explains the setup better. If you still feel the project needs more to reach Tier 2, let me know, and I am willing to design a custom PCB to improve the internal wiring.

Thanks!

12/26/2025 - Designing the case, doing the BOM and a schematic

Over the last 10 hours, I have designed a box to house our components for this home assistant box. I have also drawn up a wiring diagram for the components and a Bill of Materials.

Images

BOM (Bill of Materials)

Box

Enclosure Design Strategy:
The chassis is designed with a specific airflow path in mind. The front grills allow cool air intake, which is pulled across the Raspberry Pi heatsink and exhausted by the rear Noctua fan.

• Assembly: I moved away from self-tapping screws (which strip the plastic) and designed holes specifically for M2.5 Brass Threaded Inserts. This allows the case to be opened and closed repeatedly for maintenance without damaging the print.
• Access: The lid uses 10x2mm Neodymium magnets instead of screws for tool-less access to the GPIO pins if debugging is needed.

Inside

Internal Layout & Interference Mitigation:
A major engineering challenge with USB 3.0 on the Raspberry Pi 4 is the Radio Frequency (RF) interference it generates, which can kill Zigbee signals.

• Solution: Instead of plugging the Sonoff Dongle-E directly into the USB port, I designed a dedicated internal mounting slot at the front of the case.
• Implementation: The dongle is connected via a shielded USB extension cable. This physical separation significantly improves network stability and range compared to a direct connection.
• Cable Management: Space is reserved under the PCB standoffs to route the LED wires and fan cables, keeping the airflow path unobstructed.

Components

Exploded Assembly View:
This view demonstrates the "Stack-up" of the assembly.

1. Base Layer: The Raspberry Pi sits on 3mm standoffs to allow airflow underneath the PCB.
2. Mid Layer: The Fan (Noctua 40mm) and the Potentiometer (3362P) are friction-fitted into their slots before soldering.
3. Top Layer: The Wemos D1 Mini is mounted on the side wall to keep the Wi-Fi antenna away from the metal USB ports.

Schematic

Power Distribution & Control Logic:
The schematic details how the single USB-C power source is distributed.

• Cooling Control: To avoid software dependency for cooling, I implemented a hardware-based control loop using a 100-ohm Trimpot (RV1) in series with the Fan. This allows for a "Set-and-Forget" noise floor adjustment that cannot fail even if the OS crashes.
• Lighting: The Wemos D1 Mini is powered directly from the Pi's 5V rail and drives the SK6812 LEDs via GPIO2 (D4), providing independent status indication (Green=OK, Red=Error) controlled via Home Assistant API.