WiFi Boat Monitor - Sensors

Sensor Suite

  • Hatch boards in/out (as a burglar alarm)
    This uses a magnetic burgler alarm switch (I used the kind that mounts in a hole like the NTE 54-629).  I enable the pull-ups on the Atmel, and wire the switch so it shorts to ground.  Here is a sketch:
  • Engine On/Off (to calculate run time)
    This uses a 12V supply that turns on with the engine.  For example, the ignition key, or the supply to the electric fuel pump.  To reduce the voltage from 12V to 5V, I considered a Voltage divider, but went instead with a 5V regulator.  The 3 terminal part is easier to hook up, and gives a logic high voltage for a wide range of input voltages.
  • Interior temperature
    I used the LM335A with a 5.1K resistor.  The Voltage from the circuit is 10 mV / deg K (note the drawing below is mislabeled).  This one needs an analog input on the microcontroller to read it.  It seems to read a little hotter than it actually is, by 5 degrees or so.
  • Battery Voltage
    Just a simple voltage divider.  This drains the battery over time.  I was too lazy to think of something better, hopefully my solar panel can keep up with the mA it draws.

More to come.  A bilge water level detector would probably make sense too, but the sensors above are actually in place and working.

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