# Sum of I/O Current for Uno

Hi,

Im new in this, need to understand about these two issue related to the statement below

"Sum of currents out of all input/output pins combined: 200mA"

1. This means that if all component is turn on simultaneously right? even if i have total max current of 320mA for all of my components but not all are turn on at the same time, it should be fine, correct? for example, if i have 10 LED, only one is turned on one at a time for each second, the sum of current will only be 20mA?

2. if the su of current is 200mA only, how it is not an issue when we're using ESP-01 which some say it will use more than 200mA when transmitting?

Don't confuse I/O pins with power pins.
The 5volt power pin on an Uno can provide about 450mA on USB power.
Leo..

if the su of current is 200mA only, how it is not an issue when we're using ESP-01 which some say it will use more than 200mA when transmitting?

Simple That statement is about ATmega based Arduinos and the ESP is NOT an Arduino, let alone has an ATmega chip.

This means that if all component is turn on simultaneously right?

Right. But this is a rather oversimplified statement. It comes from the data sheet that says the maximum current for the power pins should not exceed 200mA. This means you should not have more than 200mA flowing through either the power or ground wires.

Obviously if an led is not on it is not drawing current but in theory you can have 200mA of current being sourced and 200mA of current being sunk through the processor.

However it is not that simple as limits apply to grouped of pins, for example the sum of currents being drawn from the analogue pins must not exceed 100mA. See the data sheet for the ATmega processor for a full table.

But remember an ESP is no in any way shape or form an Arduino.

It is an issue on some boards, which have a smaller 3.3V regulator than the UNO. Using those to power the ESP8266 makes them sizzling hot. When I saw that, I didn't continue to find out whether it still worked. It's not just about the regulator, it's also about the size of the PCB thermal footprint that allows the regulator to cool. This is why it is a good idea to use an ESP board that has its own regulator if you're running from 5V.