user49603: I am new to Arduino
Let me ask you about IOT(internet of things).
I want to connect ESP-01S Relay v1.0
Where does the NC port goes on Arduino? Is it TX or RX?
Also, where does the NO goes on Arduino? Is it TX or RX?


user19409: The 2 connections you refer to (NC and NO) are connections to the relay switch.

NO stands for normally open
NC stands for normally closed
C or COM stands for common


When the relay is unenergised, the common is connected to the NC terminal. When power is applied to the relay, the coil energises and switches, so now common is connected to the NO terminal.
From my reading of the usage document located on the GitHub repository, you are supposed to program the ESP module before plugging it into the relay board. There are no terminals broken out for you to connect to the Tx and Rx on the relay board.
However, the following board from AUS-eParts has a header to connect a 3V TTL cable. This can be used to program the ESP module.


49603: <p>I am new to Arduino</p>

<p>Let me ask you about IOT(internet of things).</p>

<p>I want to connect ESP-01S Relay v1.0</p>

<p>Where does the NC port goes on Arduino? Is it TX or RX?</p>

<p>Also, where does the NO goes on Arduino? Is it TX or RX?</p>

<p><a href="https://i.stack.imgur.com/otpoO.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/otpoO.jpg" alt="enter image description here"></a></p>
 19409: <p>The 2 connections you refer to (NC and NO) are connections to the relay switch.</p>

<ul>
<li><strong>NO</strong> stands for <em>normally open</em></li>
<li><strong>NC</strong> stands for <em>normally closed</em></li>
<li><strong>C</strong> or <strong>COM</strong> stands for <em>common</em></li>
</ul>

<p><a href="https://i.stack.imgur.com/RPglA.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RPglA.gif" alt="basic relay diagram"></a></p>

<p>When the relay is unenergised, the common is connected to the NC terminal. When power is applied to the relay, the coil energises and switches, so now common is connected to the NO terminal.</p>

<p>From my reading of the usage document located on the <a href="https://github.com/IOT-MCU/ESP-01S-Relay-v1.0" rel="nofollow noreferrer">GitHub repository</a>, you are supposed to program the ESP module before plugging it into the relay board. There are no terminals broken out for you to connect to the Tx and Rx on the relay board.</p>

<p>However, the following board from <a href="http://auseparts.com.au/index.php?route=product/product&amp;product_id=377" rel="nofollow noreferrer">AUS-eParts</a> has a header to connect a 3V TTL cable. This can be used to program the ESP module.</p>

<p><a href="https://i.stack.imgur.com/Qky4Y.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Qky4Y.jpg" alt="Relay board with TTL header"></a></p>
