user16754: I am looking to setup a system where I have a master Arduino polling a number of sensors. 
The way I am thinking is hooking the master TX line to the sensors RX line(and the opposite for the other line)
Questions 

How long can the lines be?
Can the lines branch?


user10794: I have a page about connecting Arduinos using RS485. You can connect multiple devices up like this:

That has a reasonable range, 20 metres or more.

On that page I describe a Rolling-master system where each device takes turns to be the master and transmit information to the other devices. It also manages some devices not responding.
This screenshot shows the various devices "talking" during their timeslot:

In that particular case there were 3 devices active out of 4 configured.


I have a master ardunio polling a number of sensors. 

I'm assuming in my answer that you have an Arduino at each sensor point (you could use a cheap ATtiny85 or something). That would be needed to run the rolling master code.

16754: <p>I am looking to setup a system where I have a master Arduino polling a number of sensors. </p>

<p>The way I am thinking is hooking the master TX line to the sensors RX line(and the opposite for the other line)</p>

<p>Questions </p>

<ol>
<li>How long can the lines be?</li>
<li>Can the lines branch?</li>
</ol>
 10794: <p>I have a page about <a href="http://www.gammon.com.au/forum/?id=11428" rel="nofollow noreferrer">connecting Arduinos using RS485</a>. You can connect multiple devices up like this:</p>

<p><a href="https://i.stack.imgur.com/auNfc.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/auNfc.png" alt="RS485 setup"></a></p>

<p>That has a reasonable range, 20 metres or more.</p>

<hr>

<p>On that page I describe a <em>Rolling-master system</em> where each device takes turns to be the master and transmit information to the other devices. It also manages some devices not responding.</p>

<p>This screenshot shows the various devices "talking" during their timeslot:</p>

<p><a href="https://i.stack.imgur.com/XB5aq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/XB5aq.png" alt="Rolling master demo"></a></p>

<p>In that particular case there were 3 devices active out of 4 configured.</p>

<hr>

<blockquote>
  <p>I have a master ardunio polling a number of sensors. </p>
</blockquote>

<p>I'm assuming in my answer that you have an Arduino at each sensor point (you could use a cheap ATtiny85 or something). That would be needed to run the rolling master code.</p>
