NFC Tap-to-Action

Last updated March 27, 2026

Overview

NFC Tap-to-Action lets you control your IoT devices by tapping a physical NFC tag with your phone or scanning a QR code. Mount tags near equipment for instant one-tap actions — toggle a fan, trigger an emergency stop, or pull up a device's dashboard.

How It Works

  1. Tap or scan — Hold your phone near an NFC tag, or scan a QR code with your camera.
  2. Opens the tap page — Your browser navigates to /tap/{deviceId} with action parameters.
  3. Action executes — If you're signed in, the action runs immediately. If not, you're prompted to sign in first and then redirected back.

The entire interaction takes about two seconds for authenticated users.

Supported Actions

Toggle Actuator

Flips a specific actuator on or off. Tapping while the actuator is on turns it off, and vice versa. Useful for: fans, pumps, lights, heaters.

Emergency Stop

Turns off all actuators in the specified room immediately. Mount an e-stop NFC tag near hazardous equipment for quick shutdown without needing to navigate the app.

Setpoint Redirect

Opens the dashboard for the device, scrolled to the setpoint controls. Useful for quick manual adjustments — tap the tag near a fermenter to jump straight to its temperature setpoint.

Device Overview

Opens the device's dashboard showing current sensor readings, actuator states, and alerts. A passive action — nothing is changed, just viewed.

Managing NFC Tags

Tags are managed in your LoopString account:

  1. Create a tag — Define the device, optional room, action type, and target (e.g., which actuator to toggle).
  2. Generate the URL — The system creates a tap URL. The URL format is:
    • /tap/{deviceId} for device-level actions
    • /tap/{deviceId}/{roomId}?action={type}&target={id} for room-scoped actions
  3. Write to NFC tag — Use any NFC writing app to write the URL as an NDEF record to a physical NFC tag.
  4. QR fallback — For users without NFC-capable phones, generate a QR code containing the same URL. Print and mount it alongside or instead of the NFC tag.

Authentication

The tap page checks if you're signed in:

  • Signed in — The action executes immediately. You see a brief spinner followed by "Success."
  • Not signed in — You're redirected to the sign-in page. After signing in, you're sent back to the tap page and the action runs.

For security, tap actions only work for authenticated users who have access to the device.

Practical Tips

  • Label your tags — Print or write the action on the tag's sticker (e.g., "Tap to toggle fan").
  • Mount near equipment — Place tags at eye level near the actuator they control.
  • Use QR codes for shared spaces — QR codes work with any phone camera, while NFC requires holding the phone close to the tag.
  • Emergency stop tags — Use a distinct color (red) for e-stop tags. Mount them prominently near any equipment that might need quick shutdown.
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