Why New WE-PN Devices Have a "Don't Just Unplug Me" Sticker
New WE-PN devices ship with a small sticker near the power port: use the power-off menu instead of pulling the plug. Here's why.
The problem
WE-PN runs on microSD cards, like most Raspberry Pi hardware. They're cheap and easy to source, but they have a known weakness: cutting power mid-write can corrupt the card.
SD cards manage their own wear leveling internally, translating the blocks the OS writes to into physical NAND flash cells using logic built into the card's controller. A power cut mid-write can corrupt that internal bookkeeping, not just the file being written. The card can stop mounting, or fail in ways that look like physical damage even though the flash itself may be fine. The exact failure mode can vary by card and manufacturer, but the pattern we consistently see is the same: sudden power loss during a write, followed by a card that no longer works reliably.
We've seen this on field devices. WE-PN runs a full Linux OS with logs and state files that get written regularly, and it can lose power unexpectedly whenever someone unplugs it, which is exactly the combination that puts a card at risk.
Why this feels unfamiliar
Most household electronics don't train people to expect this. A microwave has no persistent storage that can corrupt: cut the power and it just turns back on. A typical home router does have flash storage, but it mostly runs a fixed, read-only firmware image and writes to disk rarely, so a power cut is unlikely to catch it mid-write. Laptops and phones write constantly, but they almost always have a battery buffering them, so the OS gets a clean shutdown before the power actually disappears.
WE-PN devices fall into a gap between these: a full Linux system that writes to disk regularly, with no battery to soften a sudden power cut. That combination is uncommon enough in consumer hardware that there's no existing habit to fall back on. Hence the sticker.
Why not just use an SSD
SSDs handle power loss better: many have power-loss protection, better wear leveling, and firmware built for sustained random I/O.
The problem is cost. Flash storage prices have risen sharply industry-wide, and SSDs need different connectors and power delivery than a microSD slot. We want to keep the device affordable, and switching to SSDs now would mean passing that extreme cost increase straight on to you. We are working on a longer term solution, which might involve SSDs as an option.
What we're doing instead
- Warning stickers, since accidental power loss is the biggest single cause
- Moving toward a read-only root filesystem with an overlay for writable state, and more crash-resilient filesystems
- Cutting unnecessary writes (e.g. tuning or disabling swap) to shrink the window where a power cut can do damage
- Evaluating industrial-grade cards built with MLC or SLC flash, rather than consumer TLC/QLC, for future hardware
None of this eliminates the risk alone, but together it cuts down how often it happens and how bad it is.
The takeaway
Use the power-off option before unplugging your device. It's a small habit that avoids most card failures, and we're working on making the hardware more resilient to this over time.