Silent Alarm

Silent Alarm: Time-Delayed Condition Triggers

The Silent Alarm trigger provides time-delayed workflow execution, ensuring that conditions persist for a specified duration before triggering automation. This is essential for filtering out transient spikes, preventing false alarms, and confirming sustained conditions before taking action.

Info: This is a Trigger node type that can be used to trigger workflows based on sustained conditions. Unlike instant triggers, Silent Alarm waits for a configurable delay period before executing its child nodes, providing confirmation that a condition is persistent rather than momentary.

Overview

Silent Alarms add temporal intelligence to your automation workflows. Instead of reacting immediately to every condition change, they wait to see if the condition persists. This prevents unnecessary actions from brief anomalies, sensor glitches, or temporary fluctuations.

Key Features

• Configurable Delay: Set delay period in milliseconds
• Sustained Condition Detection: Only triggers if condition persists
• False Alarm Prevention: Filters out transient spikes
• Background Monitoring: Uses coroutine-based timer for efficiency
• Automatic Cancellation: Resets if condition clears before timeout
• Visual Feedback: Shows when alarm is pending vs triggered

Silent Alarm Operation Flow

graph TD
    A[Condition Met] --> B[Start Silent Alarm Timer]
    B --> C{Delay Period Elapsed?}
    C -->|No| D{Condition Still True?}
    D -->|Yes| C
    D -->|No| E[Cancel Alarm]
    C -->|Yes| F{Condition Still True?}
    F -->|No| E
    F -->|Yes| G[Set to EXECUTED]
    G --> H[Execute Child Nodes]
    H --> I[Perform Actions]

How It Works

The Silent Alarm operates through a time-delayed trigger mechanism:

1. Condition Detection: Initial condition is met (e.g., temperature exceeds threshold)
2. Timer Start: Silent Alarm begins countdown using configured delay period
3. Continuous Monitoring: Checks if condition remains true throughout delay
4. Early Cancellation: If condition clears during delay, timer resets
5. Confirmation: After full delay elapses, verifies condition is still true
6. Trigger: Transitions to EXECUTED state and activates child executors
7. Action: Child nodes perform configured automation responses

Configuration

Field	Description	Required	Default
delayMs	Delay period in milliseconds	Yes	0

Common Delay Periods

Duration	Milliseconds	Use Case
5 seconds	5000	Brief confirmation
30 seconds	30000	Short validation
1 minute	60000	Standard delay
5 minutes	300000	Extended confirmation
15 minutes	900000	Sustained condition
1 hour	3600000	Long-term monitoring

Use Cases

• Temperature Stability: Confirm temperature has stabilized before action
• Pressure Alarms: Ensure pressure anomaly isn’t transient
• Motion Detection: Verify sustained motion before triggering security
• Network Monitoring: Detect genuine outages vs brief disconnects
• Equipment Monitoring: Confirm equipment fault before shutdown
• Resource Alerts: Verify resource depletion is sustained
• Environmental Monitoring: Filter out sensor noise in readings

Example Workflows

High Temperature with Confirmation:

1. Trigger: High Threshold (Temperature > 80°C)
2. Trigger: Silent Alarm (30 second delay)
3. Executor: Logic Gate (final verification)
4. Executor: Pin Control (activate cooling)
5. Executor: OutgoingWebHook (send alert)

Sustained Motion Detection:

1. Trigger: Pin State Change (motion sensor)
2. Trigger: Silent Alarm (5 second delay)
3. Executor: Pin Control (turn on lights)
4. Executor: OutgoingWebHook (security notification)

Network Outage Detection:

1. Trigger: Low Threshold (connectivity < 1)
2. Trigger: Silent Alarm (2 minute delay)
3. Executor: Lambda (check alternative connection)
4. Executor: OutgoingWebHook (IT alert)

Equipment Overload Protection:

1. Trigger: High Threshold (current > 10A)
2. Trigger: Silent Alarm (10 second delay)
3. Executor: Logic Gate (safety check)
4. Executor: Pin Control (trip breaker)

Combining with Other Triggers

Multi-Stage Alarm System:

High Threshold → Immediate: Visual alert
              → Silent Alarm (1 min) → Warning notification
              → Silent Alarm (5 min) → Emergency response

Hysteresis with Delay:

High Threshold → Silent Alarm (30s) → Activate Cooling
Low Threshold → Silent Alarm (60s) → Deactivate Cooling

This creates a delayed hysteresis system that prevents rapid cycling.

Advanced Patterns

Cascading Silent Alarms:

graph TD
    A[Condition Detected] --> B[Silent Alarm 1: 30s]
    B --> C[Warning Level Action]
    B --> D[Silent Alarm 2: 2 min]
    D --> E[Alert Level Action]
    D --> F[Silent Alarm 3: 5 min]
    F --> G[Emergency Level Action]

Conditional Delayed Response:

Condition AND Business Hours → Silent Alarm (1 min) → Normal Response
Condition AND After Hours → Silent Alarm (30s) → Urgent Response

SilentAlarmMonitor Service

Behind the scenes, Silent Alarms use the SilentAlarmMonitor service which:

• Manages coroutine-based timers for each alarm
• Efficiently handles multiple concurrent alarms
• Automatically cleans up completed timers
• Provides non-blocking operation

Integration Points

• Thresholds: Combine with high/low thresholds for sustained condition detection
• Data Points: Monitor data point values over time
• Pins: Detect sustained pin states
• Logic Gates: Add logical conditions to delayed triggers
• Executors: Trigger any executor after delay confirmation

Best Practices

• Appropriate Delays: Match delay to condition characteristics
  • Brief spikes: 5-30 seconds
  • System stability: 1-5 minutes
  • Long-term trends: 15+ minutes
• Layered Approach: Use multiple delays for graduated responses
• Cancel Logic: Ensure conditions can clear to cancel alarms
• Testing: Verify delays work as expected in development
• Documentation: Document why specific delays were chosen
• Monitoring: Log alarm activations and cancellations
• Backup Systems: Have manual override for critical alarms

Preventing False Positives

Silent Alarms excel at eliminating false positives:

Scenario	Without Silent Alarm	With Silent Alarm
Sensor Glitch	Immediate false alarm	Ignored (clears in < delay)
Brief Spike	Unnecessary shutdown	No action (spike subsides)
Actual Problem	Quick response	Confirmed response
Network Blip	False outage alert	Ignored (reconnects quickly)

Typical Delay Recommendations

Condition Type	Recommended Delay	Reason
Sensor Reading	10-30 seconds	Filter noise
Temperature	30-60 seconds	Allow stabilization
Pressure	15-30 seconds	Confirm sustained change
Motion	3-10 seconds	Ignore brief movement
Network	1-2 minutes	Skip brief disconnects
Equipment	30-60 seconds	Confirm fault

Comparison with Instant Triggers

Feature	Instant Trigger	Silent Alarm
Response Time	Immediate	Delayed
False Positives	High	Low
Use Case	Emergency stop	Confirmed conditions
Complexity	Simple	Moderate

Monitoring and Debugging

Track Silent Alarm behavior:

• Activation Count: How often does alarm start?
• Cancellation Count: How often is alarm cancelled?
• Trigger Count: How often does full delay elapse?
• Average Duration: How long between start and trigger?

This data helps optimize delay periods.

Silent Alarms are essential for building intelligent automation systems that respond to genuine, sustained conditions rather than reacting to every transient fluctuation.