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How too know whether digitalwrite(HIGH, pin_number) sets the voltage to 5 volts or 3.3 volts. I am yet to purchase arduino uno. I want digital pin voltage to be 5 volts. I am aware that thereis a pin already have 5 volts but I want to know only about the voltage output at digital pins.

Sorry if question is too silly. I am not very knowledgable in Electronics.

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Different boards operate internally at different voltages. This is dictated by the main chip on the board. That main internal operating voltage is also the voltage at which the IO pins operate.

Most "old" Arduino boards operate at 5V. This includes, but is not limited to:

  • Arduino UNO
  • Arduino Mini
  • Arduino Leonardo

Newer more powerful boards, many made by other companies, operate at 3.3V. Again, this includes such boards as:

  • Arduino DUE
  • Arduino MKR1000
  • Teensy boards (v3.0+)
  • chipKIT boards
  • ESP8266 & ESP32 boards

Some boards come in variants that give either voltage - the most notable being the Pro Mini boards from Sparkfun. These come in both 5V and 3.3V variants and it is important to pick the right board for your needs.

In general, though:

  • If it's 8-bit and runs on an ATMega chip it's likely 5V unless otherwise stated
  • All 32-bit boards will be 3.3V unless otherwise stated.
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When you use digitalWrite(pin_Number,HIGH); this sets the output pin to 5 V but still if you want to check the voltage you can you a digital multi meter set its knob to DC voltage and connect its positive to the pin and the ground pin to ground and the voltage will be displayed on the multi meter

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  • Thanks, but this link says HIGH depends on 5volt board or 3.3 volt board arduino.cc/reference/en/language/functions/digital-io/… . How to know Arduino Uno is 5 volt board or 33 volt board ?
    – Hitesh Somani
    Commented Sep 28, 2020 at 9:58
  • @HiteshSomani: It's 5 V, written very prominently on the product page.
    – Edgar Bonet
    Commented Sep 28, 2020 at 10:37
  • The Uno is a 5V Arduino. For other types the answer is more complicated, as explained in Majenko's excellent answer.
    – Duncan C
    Commented Sep 28, 2020 at 13:11

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