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Answer:
IFTTT time-based routines may run twice when linked to Zigbee presence sensors
because the sensor often sends duplicate presence events—for example,
rapid “present → absent → present” transitions caused by signal fluctuations.
When IFTTT receives multiple triggers within a short window, it can interpret
each one as a fresh event, causing the routine to execute twice.
Preliminary
Diagnostic Steps
1. Check Zigbee
Event Logs
In your smart hub
(SmartThings, Home Assistant, Hue Bridge, etc.), check the device’s activity
history.
If you see multiple presence updates within seconds, the sensor is generating
duplicate triggers.
2. Test the
Sensor’s Distance and Signal Strength
Presence sensors may
momentarily disconnect due to:
- Weak Zigbee mesh
- Interference from Wi-Fi or Bluetooth
- Overcrowded channels
Signal drops can cause
the sensor to briefly report as “absent” then immediately “present.”
3. Inspect IFTTT
Trigger History
IFTTT keeps a log of
each automation execution.
If the log shows two triggers at the same timestamp or within a 1–3 second
window, the trigger source is duplicating events, not IFTTT.
4. Disable Presence
Trigger Temporarily
Run the same routine
using only the time-based trigger.
If it executes once, the issue is directly tied to the Zigbee presence sensor.
Step-by-Step
Technical Fix
1. Add a “Cool-Down
Window” to IFTTT
In IFTTT Pro, use
filters or code to prevent a second execution within a set window (e.g., 30
seconds).
This blocks duplicate presence reports from triggering the routine twice.
2. Adjust the
Zigbee Channel
Change your Zigbee
coordinator to a cleaner channel (often 15, 20, or 25 depending on Wi-Fi
congestion).
A stable channel reduces micro-disconnects that cause rapid presence toggling.
3. Improve Zigbee
Mesh Coverage
Add one or more Zigbee
routers (smart plugs or bulbs).
A stronger mesh minimizes presence flapping and prevents double triggers.
4. Replace Battery
in Presence Sensor
Low-battery sensors
often behave unpredictably.
Replace the battery to stabilize presence reporting and eliminate false
triggers.
5. Reduce Physical
Obstructions
Walls, metal
appliances, and long distances can cause intermittent disconnections.
Reposition either the hub or the sensor to maintain a consistent link.
6. Create Logic in
Your Main Hub Instead of IFTTT
If using SmartThings
or Home Assistant:
- Build the presence logic there
- Trigger IFTTT only once from a stable
virtual switch
This eliminates
duplicate sensor signals from reaching IFTTT.
Preventing Future
Double-Execution
1. Run Presence
Through a “Stabilizer” Device
Use a virtual presence
sensor with built-in delay or debounce logic to filter noisy Zigbee events.
2. Avoid Mixing
Time Trigger + Presence Trigger Directly
In many cases, IFTTT
sees:
- Time event
- Presence event
…as two separate triggers, leading to double execution.
Instead, use presence only to enable the time trigger.
3. Keep Your Zigbee
Network Low-Interference
Avoid Wi-Fi channels
that overlap with your Zigbee channel.
Less interference = fewer phantom presence reports.
4. Update Firmware
Regularly
Zigbee hubs and
sensors receive stability patches that reduce duplicate events.