Engineering · 2024

Live Monitoring App for Wireless Temperature Sensors

An always-on display of cloud-stored sensor readings, with alerts when a reading leaves the configured range

Sensor readings that previously required logging into a web dashboard are now shown continuously on a PC at the site, with an on-screen and audible alert the moment a reading leaves the configured range.

Client
Confidential client
Category
Engineering
Full-screen monitoring view with the temperature chart and current, highest and lowest readings

Overview

  • Desktop program showing readings that wireless temperature sensors upload to the cloud
  • Built for site staff who need to watch temperature continuously
  • Launch → cloud sign-in → set alarm limits → monitoring view
  • Target sensor, displayed time span and refresh interval set in a configuration file
Full-screen view for an always-on display
Full-screen monitoring

Challenge

  • Readings available only through the sensor vendor's web dashboard, requiring repeated sign-ins
  • No alert on an out-of-range reading, so it went unnoticed until the next check
  • No always-on display readable from a distance

Solution

  • Recent temperature history drawn as a single line chart
  • Current, highest and lowest temperature shown beside the upper and lower limits in large figures
  • Current, highest and lowest points plus both limit lines marked on the chart by color
  • Limits adjustable on the spot, applied to chart and panels immediately
  • Full-screen mode for a dedicated monitor
Monitoring view with current, highest and lowest temperature and the limit lines
Monitoring view
  • On-screen warning plus a repeating alert sound whenever the current reading leaves the range
  • Warning and sound cleared automatically once the reading returns to range
Warning shown after the current temperature passes the upper limit
Out-of-range warning

System architecture

Flow

  • Wireless sensor → vendor cloud → periodic lookup by the program → chart and figures → alert on range exit
  • Readings taken every 3 minutes, with a 150-minute span on screen by default
  • Sensor to watch and refresh interval changed in the configuration file
Cloud sign-in and alarm limit window
Sign-in and alarm limits

Implementation

  • Cloud timestamps offset from local time → lookup window corrected so the recent span lines up
  • Gaps from readings the sensor failed to upload → filled from surrounding values to keep the line unbroken
  • Last reading older than 30 minutes → prompt to check the sensor, so stale data is not read as current
  • Title and figure sizes scaled to the window → legible from a distance on a large monitor
  • Alert playback kept separate from screen updates → the chart keeps refreshing during an alert
  • Distributed as an executable, with no installation step

Result

  • Current temperature and recent trend visible without opening the web dashboard
  • Range violations noticed as they happen instead of after the fact
  • One always-on monitor giving several people the same view at once
  • Alarm limits changed on site as conditions require

Technology

  • Python
  • wxPython
  • matplotlib
  • REST API
  • PyInstaller

Screens

Monitoring window showing the recent temperature chart with upper and lower limit lines
Monitoring view
Screen with the warning badge lit after the current temperature passed the upper limit
Out-of-range warning
Window for cloud sign-in and for setting the upper and lower alarm limits
Sign-in and alarm limits

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