Power budget and shutting down safely

A typical Stratux draws about 0.75–1 A, so use a good 5 V supply or power bank that reliably delivers 2.1 A or more, with a short, undamaged cable. To shut down, use Shutdown on the web UI Settings page. Wait for the Stratux Wi-Fi network to disappear, then remove power. Don't rely on the LEDs.

How much current Stratux draws

These are measured figures with GPS and AHRS running. Your numbers will vary with the exact hardware.

Configuration Approximate draw
Two SDRs 990–1100 mA
One SDR plus one low-power SDR 700–740 mA
Pong 390–420 mA
Pi 3B+ with GPS, 978 and 1090 radios about 750 mA average
Pi 4 with the same setup about 850 mA average
  • A UATradio uses a fraction of an SDR's power. A UATradio plus an SDR draws noticeably less than two SDRs.
  • A Pi 3B draws less than a 3B+. A Pi 4 draws roughly 50–75 mA more than a Pi 3B.
  • One report ran a 10,000 mAh bank for about 8 hours on a Pi 3B+.
  • Two SDRs on a Pi 4 browned out a few times, so we don't recommend that combination.

Choosing a supply or power bank

  • A Pi 3B needs a 5.1 V supply of at least 2.5 A. 3 A is more stable. See Power and status lights for the general 2 A rule.
  • Pick a power bank that reliably delivers 2.1 A. Dual-SDR setups need more headroom.
  • In the aircraft, use a dedicated 12 V-to-USB supply. Many aircraft USB ports give only 0.5 A, and powering from avionics risks interference. A cigar-lighter port with a long cable works and follows the master switch.
  • If you fly with a bank, check the airline's battery limit. One report says a 99.36 Wh pack stays under the common 100 Wh carry-on limit, but check the rule yourself.
  • The cable matters more than the brick. Most power problems trace back to a poor, worn or bent USB cable.

Reboots when the unit is moved

Reboots when you move the unit, Wi-Fi drops, GPS or AHRS dying, and USB errors like "device descriptor read error -32" all point to power. Work through these in order:

  1. Swap the cable.
  2. Try a different power brick.
  3. Check the micro-USB port on older Pis. It wears loose. Unplug at the far end of the cable to spare it. The Pi 4's USB-C connector is sturdier.
  4. Check the red LED. It is hardware-only. Solid means adequate voltage, and blinking or dark means low voltage.
  5. Remove extra USB loads. A cheap generic RTL2832U SDR can brown out a Pi 3B/3B+ even on a 5 V 3 A supply. A Nooelec Nano or the Stratux low-power SDR avoids this. A charging battery in a T-Beam or T-Echo can do the same, so remove it.
  6. Check for heat if the unit goes dark after a few minutes. A fan helps more than case colour.

Shutting down safely

  1. Open the web UI Settings page and tap Shutdown, then confirm. It syncs the filesystem and powers the Pi off.
  2. Wait for the Stratux Wi-Fi network to disappear from your device's network list.
  3. Remove power, or switch off the aircraft master.

The green LED is not a reliable shutdown indicator. What the LEDs do after shutdown depends on the power supply. The in-app help suggests waiting for the status light, but the Wi-Fi network disappearing is the better cue.

Some power supplies and USB battery packs see the load drop after shutdown and reboot the Pi instead of staying off. That can be harder on the SD card than pulling power. If your unit won't stay off, suspect the supply, and pull power once the network is gone.

Many experienced users with the read-only overlay filesystem enabled simply pull power. That lowers the risk, but an unclean shutdown can still corrupt stratux.sqlite. Whether pulling power is always safe is still unsettled, because some units have stopped broadcasting their network after power was cut.

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