LoRaWAN/WiFi signal penetration issues in a steel-framed portable office?

Projects Networking, Protocols, and Devices
1

Hi everyone,

I am working on an IoT monitoring project for a remote site office. I’m using an Arduino Mega with an ESP8266 for WiFi and a DHT22 for climate tracking.

The challenge is the environment: the office is a heavy-duty porta cabin which has metal cladding and steel framing.

Because the structure is essentially a large metal box, I'm running into two main issues:

Signal Shielding: My WiFi signal drops significantly as soon as the door is closed (Faraday cage effect). Has anyone had success using an external SMA antenna pigtail through a sandwich panel wall without causing moisture/leaking issues?

EMI/Power Noise: The cabin is powered by a site generator. I'm seeing a lot of "noise" on my analog sensor pins when the AC unit kicks in. Would a simple LC filter on the 5V rail be enough, or do I need a fully isolated DC-DC converter for the Arduino?

Grounding: Since the frame is steel, should I ground my project's GND to the cabin's chassis, or is that risky if the site ground isn't perfectly stable?

I want to ensure the hardware survives the rugged environment of these units. Any advice on "industrializing" this setup would be great!

Thanks!

2

It sounds lke you have identified most if not all the issues and also answered them, but to be clear.

  1. Do the external antenna, just seal everything with a sealant like hot glue or silicone.
  2. As far as the noise, use standard filtering on the Arduino as close to the Arduino pins as possible, not the power rails. Also consider adding filtering to the A/C even if only a commercial plug-in type.
  3. Ground MUST be solid, NOT the cabin. Since you are NOT connected to mains but are using a generator, is it a proper inverter style or a cheap contractor style? Second, is it properly grounded or, as is often the case, floating. Even on my top-of-the-line Honda inverter generators, I had to use a grounding plug because Honda refuses to wire them correctly.
3

Have you considered using a wired connection, it would be just accessible and the metal problem goes away. Another option would be to place a WiFi extender in a weather plastic or wooden box just outside the structure.

4

No need to run cable through a metal wall. There are lots of bulkhead mounting coax connectors that are totally waterproof. You just have to look.