I would like to be able to design an Arduino circuit for a fridge monitor that would have a temperature sensor, a small speaker to emit a sound when the temperature changes past a threshold and an LCD screen showing the current temperature.

I have found a few examples online, but I would like to know why components like capacitors and transistors are used in their circuits so I'd be able to design similar circuits myself.

I found this list of electronics topics:

  • Basic Theory
  • Basic Passive Components
  • Passive Circuits
  • Discrete Active Components
  • Active Circuits
  • Integrated Circuits
  • Digital Logic
  • Analog
  • Signals
  • Outputs
  • Inputs
  • Digital Electronics

Some of these things, like digital logic seem unnecessary in such a project, but obviously some others are useful, but I don't know which. I'd like to know what it would be useful to study so I can understand the reasons for the circuit design of something like a fridge monitor.

  • You're going to need a large portion of that in order to do more than just banging rocks against other rocks and hoping you get a useful tool. Aug 4, 2014 at 22:26
  • ...or you can pick a goal you want to accomplish, and learn what you need to in order to enable it (while being open to discovering that you need to alter your goal in light of practicalities you learn about) Aug 4, 2014 at 22:30
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    I voted to reopen this. I removed the lamp since that's a whole other question :) Feel free to ask another question if you wish to do so. Aug 5, 2014 at 23:41
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    And now we get to "It depends on what pieces you want to use.". You handle a thermocouple very differently from e.g. a TMP36. A coil speaker vs. a piezo buzzer. A bare segmented LCD vs. a HD44780U-compatible module. Aug 6, 2014 at 0:07
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    Why don't you pick one of the circuits you found online, the one you find most interesting, study it a little, then post your specific questions here (or at EE.SE)? Pick a simple circuit that features only one of the components you described (temp sensor or speaker or LCD). Don't forget to post the link to the circuit and make sure there's a schematic for the EE folks to look at. That's how our site works best - to answer specific questions users have.
    – Ricardo
    Aug 7, 2014 at 17:34

1 Answer 1


A fridge temperature monitor (or any system that talks to world using some data) will include a sensor (temperature sensor like LM35), a controller (to do calculations, arduino ofcourse) and an output (display, like LCD). The topics you should be aware of, are digital electronics, basic passive components (working of resistor, capacitor etc). And a little arduino programming and lots of logic.

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