The Sting's light sensor can be used as a tamper detection mechanism. 


This is a beta feature in firmware version 1.1.


Background

Lux is a measure of light intensity, as perceived by the human eye. Wikipedia explains the concept and provides a useful scale of example lux levels. The Sting can wakeup at preset lux levels. This can be used to indicate a tamper in a sealed box - when the lid opens, the Sting wakes up and reports the tamper.


Approach

The approach take in the Sting firmware is to provide 2 lux thresholds. If the sensor detects a light level above the high threshold, a tamper is triggered. When the light level drops below the low threshold, the tamper is cleared. The difference between the high and low thresholds provides some hysteresis. A time threshold is also provided - the light level must cross the threshold for more than the time threshold to trigger the tamper.


If a tamper is detected, the Sting will immediately log a Digital Input Changed record. If the module settings dictate an upload, it will then attempt to get a GPS fix and a subsequent upload.


Firmware

The feature is available in version 1.1 on the OEM Server.


Settings: 

The default setup is DISABLED.

To enable the module, be sure to set the Tamper Digital Input to something other than Disabled.


Settings can be changed in the OEM Server Admin Interface using the System Parameters.


The following settings are recommended as a starting point:

  • Tamper level: a lux measurement above this level will trigger a tamper. A seemly low default value of 3 works for well sealed parcels.
  • Tamper reset level: once the tamper is active, it is reset if the lux measurement drops below this level. A default value of 2.5 works with the high level of 3.
  • Time threshold (milliseconds): how long the light level must exceed the threshold to trigger the tamper. The default is 50ms.
  • Digital Input: which input to set on tamper. The default is disabled. Input 1 is commonly used when enabled.
  • Invert tamper: this allows the lack of light to be considered a tamper condition. A level below the Tamper Reset Level will turn tamper ON.
  • Upload/Emergency upload: control how the Sting should respond to a tamper.

Alerting on Telematics Guru:

Should you wish to alert based on the tamper in Telematics Guru:

  • Ensure the IO mapping is setup for the digital input. If input 1 is selected in the settings above, use the default IO mappings on TG - these are set for input 1.
  • Create an alert on a Digital Input Change, and select Input 1. A change to Active is most useful. An example is show below:


Testing:

To get started, select the correct firmware. Enable the module by selecting Digital Input 1 as the Tamper Digital Input. Wait for the initial LED flashing to stop before testing. Use the default lux levels as a starting point.


Please test and verify your tamper setup in extreme situations. 


Troubleshooting:

  1. Ensure your LED settings do not trigger the tamper.