As I embark on my first Arduino project, I have lots of questions. Specifically, what considerations should I make when selecting equipment, and what are the critical parameters to safe operation?

Some elaboration upon my questions can be seen below. However, outlining general principals of equipment selection would be highly useful.

I have an Arduino Uno. The Uno has an input voltage of 6-20 V, and operating voltage of 5 V as from the tech specs. Does this mean that I can select any sensor with less than 20 V output to send data to my Arduino?

I am interested in using a sensor like this Texas Instruments HDC1080 High Accuracy Digital Humidity Sensor, which has a supply of 5.5 V. If my logic is correct, this output should be fine. I should know whether or not I need to buy some sort of shield based purely upon the output pins of the sensor, correct? I know I have 6 analog and 6 PWM/digital pins on the Arduino, so the digital signal should be capable of being processed by my Arduino. However, the interface type on the sensor product is I2C, but I am unsure as to what this means or if it needs to be a consideration.

  • For sensors, display and other accesories, prefers those with I2C (TWI) interface. They make things easier, because all of them use the same pins A4 & A5, so you will never run out of pins. Also, always look for 3.3v/5v compatibilidad, because things are moving to the 3.3v zone.
    – user31481
    Commented Jun 29, 2017 at 15:01

2 Answers 2


One question you have (3rd paragraph) brings a caution to mind. Your inputs to the Arduino are typically going to be 5v based, either digital or analog, although I may be phrasing this slightly loosely. A sensor not of the type you reference would provide a digital signal (Low/High relative to ground) or analog, which would be limited via external circuitry to 5v or lower. I think there's a good chance that if you find and use a sensor that pumps 20v into your Arduino, the smoke might be released.

I've read over the sensor you've linked. It was fascinating reading. It appears that the device is focused on being connected to a PC with USB and a Windows interface, but permits direct register access for specific data.

You'd want to research the best way to connect an i2c device to your Arduino, and I'm certain there are plenty of libraries for that. A good place to start is the reference on the "official" Arduino web site for i2c. This same page references use of the library, calling/polling the device and reading/writing data.

What I read in the volumes of the data sheets and user guides for the device you linked appears to cover everything you need to know and a tremendous amount of information you may not need.

It looks like a fun project and well engineered, at least from the sensor reference. Temperature Sensor

  • To be clear, you are saying that although the arduino specs say that my input voltage is up to 20 V, I really should stick to near 5?
    – User2341
    Commented Jun 28, 2017 at 23:40
  • Your input voltage for powering the Arduino may be as high as 20v, but the signals the unit can safely handle should be limited to 5v and there's a possibility that some devices will restrict this to 3.3v, but my brain cells are on hiatus at the moment and I'm not confident about the last statement. Excessive voltage to power the Arduino will also be shed as heat via the regulator circuit.
    – fred_dot_u
    Commented Jun 29, 2017 at 0:08
  • I think you are correct that some boards like the arduino pro have a smaller limit of 3.3v, but what is input voltage supposed to mean if not the signal voltage that you can feed into the board?
    – User2341
    Commented Jun 29, 2017 at 0:09
  • One quick add here. I did a search for maximum power for Arduino and the search results return a maximum of 12v for the Arduino Uno. Most of the projects I've built have used either six or nine volts to power the board. Twelve volts may not create excessive heat, as the board is rated to handle that level.
    – fred_dot_u
    Commented Jun 29, 2017 at 0:12
  • "what is input voltage supposed to mean if not the signal voltage" The input voltage in this case refers only to the power supplied to the Arduino board for powering the MCU and will be regulated down to 5v. Excess power will be dissipated by the regulator as heat. From the point of view of the MCU, both its operating voltage and its input signals are expected to be 5v. (This is a slight simplification; the MCU could, on a differently designed board, be run at somewhat lower voltages.)
    – JRobert
    Commented Jun 29, 2017 at 18:40

For your first project, power the Arduino Uno with the USB cable and use everything at 5V.
There are tutorials which guide you step-by-step to make something. The Adafruit tutorials are very good.

The HDC1080 is a sensor that works at 3.3V and at 5V. That means you can use it with the 5V Arduino Uno without problem.
This Tindie HDC1080 module points to a HDC1080 library on Github. I suggest you try to make that work.

If you can not get data out of the sensor, then you should start with something very simple. A few leds (with series resistors) or a LDR light sensor is fun to start with.

As soon as you start using higher voltages (for example 12V) you might consider buying a spare Arduino Uno, because the Arduino Uno will be blown when 12V touches one of the pins.

Be also careful with sensors that can only handle 3.3V and not 5V. Since the Arduino Uno runs at 5V, a pin of the Arduino could feed 5V into the sensor and damaging the 3.3V sensor.

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