By Karel Cermak | Karlosoft.
A simple Arduino project that monitors the state of the mains power supply and the backup power supply.
- Monitors the mains power supply and the backup power supply (via USB).
- Indicates the current state with status LEDs.
- Sounds a buzzer when the backup power supply is disconnected.
- Serves simple JSON statistics through a built-in web server.
- Includes a DHT22 temperature and humidity sensor and a button to mute the buzzer and the ceiling light.
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Everything OK (1)
- Blue LED blinking slowly
- Orange LED off
- Red LED off
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DHT sensor error (2)
- Blue LED blinking fast
- Orange LED blinking slowly
- Red LED off
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Ethernet error (3)
- Blue LED blinking fast
- Orange LED off
- Red LED blinking slowly
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Mains power off (4)
- Blue LED off
- Orange LED blinking fast
- Red LED off
- Ceiling light off
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Backup power off (5)
- Blue LED off
- Orange LED off
- Red LED blinking fast
- Ceiling light on
- Buzzer on
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Hold the button for 0.5 seconds
- Mutes the buzzer for 30 minutes.
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Hold the button for 5 seconds
- Mutes the buzzer and turns off the ceiling light for 12 hours.
- If the web server only starts working after you press the Arduino's reset button, the following may help:
- Connect a 100 nF capacitor between the RESET and GND pins (a larger capacitor should also work).
- Connect 100 Ω resistors between Ethernet pins 1–2 and 3–6 (untested).