Documentation is outdated for Arduino MKR 1500, I need to update it. Please check .ino file for latest information. Important changes: new screen, arduino_secrets.h file, slightly different cabling.

Arduino aquarium monitor with alarm

Arduino based aquarium alarm which checks temperature and supply voltage and alarms by SMS.

It includes a small piezo buzzer which makes alarm beeps if the temperature to high. A display that shows the current temperature and a backup battery.

Please read the text inside the .ino sketch, there are some fields you have to modify (most importantly your mobile number).

The design

Please note, the temp sensor is the wrong model on this image. It also doesn't need to be attached to the breadboard, this is just for illustration!

Required parts:

• Adafruit FONA 32u4
  • https://www.adafruit.com/product/3027
• Adafruit GSM Antenna
  • https://www.adafruit.com/product/1991
  • In my case this antenna tends to create a crash of the Arduino because of the short cable, see the FAQ of the 32u4
  • There is a variant with longer cable, I haven't tested it: https://www.adafruit.com/product/3237
  • I solved it by putting a small ferrit core around the antenna cable
• 12-pin and 16-pin feather stacking headers
  • https://www.adafruit.com/product/2830
• 500 mAh 3.7 V battery, better at least 850 mAh (to high capacity will cause long delays in the power alarm!)
  • https://www.adafruit.com/product/258 (this is the 1200 mAh model)
• micro SIM card with support for 2G (GSM), check your operators, some are starting to turn of GSM
• Breadboard with 40 or more rows
• at least 20 dupond jumper wires
• 10k resistor potentiometer for the LCD
  • https://www.arduino.cc/en/Tutorial/LiquidCrystalDisplay (PINs adjusted in this sketch, see below)
• 1602A Char LCD / 3.3V / Standard ST7066/HD44780 (must be a special 3.3V! one)
  • https://www.aliexpress.com/item/3-3V-LCD1602-LCD-monitor-1602-Blue-Screen-White-Code-Blacklight-16x2-Character-LCD-Display-Module/32453954557.html
• Piezo speaker (also known as buzzer)
• 100 Ohm resistor (for piezo)
• 220 Ohm resistor (for LCD)
• DS18B20 temp sensor with DFR0055 Plugable Terminal adapter (jumper set to Pull Up)
  • https://www.aliexpress.com/item/DS18b20-Water-Temperature-Sensor-Stainless-Steel-Probe-Temperature-Sensor-for-Arduino-SR002/32538132994.html
  • this sensor is sadly NOT salt water resistant, it requires you to protect it from direct water contact or it will quickly corrode/rust. I suggest using a tiny bit of aquarium safe silicone or synthetic resin. The thicker the layer, the slower the registered temparature change, so make it thin!
  • Manual DFR0055 https://www.dfrobot.com/wiki/index.php/Terminal_sensor_adapter_V2_SKU:DFR0055