# Node ID for EmonTx5 with Expansion Board

**URL:** <https://community.openenergymonitor.org/t/node-id-for-emontx5-with-expansion-board/28836>\
**Category:** emonTx\
**Created:** [12 July 2025 12:08 UTC](https://community.openenergymonitor.org/t/node-id-for-emontx5-with-expansion-board/28836 "2025-07-12T12:08:23Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![macrowe777](https://community.openenergymonitor.org/letter_avatar_proxy/v4/letter/m/4da419/32.png) [@macrowe777](https://community.openenergymonitor.org/u/macrowe777)\
**Post date:** [12 July 2025 12:08 UTC](https://community.openenergymonitor.org/t/node-id-for-emontx5-with-expansion-board/28836/1 "2025-07-12T12:08:23Z")

</div>

This is more an FYI for future users (or myself) as I cant find it documented. It appears EmonTx devices with expansion from 6 to 12 channels are programmed to have the first 6 channels as Node ID = N and the second 6 channels then got Node ID = N+1.

Therefore if you already have node ids used 27,28 and 29. Youll need to set the node id of the additional unit to 25, so that it will automatically assign the expansion board as 26.

---

<div class="post-metadata">

**Author:** ![awjlogan](https://community.openenergymonitor.org/letter_avatar_proxy/v4/letter/a/9e8a1a/32.png) [@awjlogan](https://community.openenergymonitor.org/u/awjlogan)\
**Post date:** [12 July 2025 14:12 UTC](https://community.openenergymonitor.org/t/node-id-for-emontx5-with-expansion-board/28836/2 "2025-07-12T14:12:33Z")

</div>

Hi @macrowe777 - definitely better for most users to be in the text documentation, but it’s described in the [source file](https://github.com/openenergymonitor/avrdb_firmware/blob/master/emon_DB_12CT/emon_DB_12CT.ino).

---

<div class="post-metadata">

**Author:** ![Robert.Wall](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/robert.wall/32/38246_2.png) [@Robert.Wall](https://community.openenergymonitor.org/u/Robert.Wall)\
**Post date:** [12 July 2025 14:17 UTC](https://community.openenergymonitor.org/t/node-id-for-emontx5-with-expansion-board/28836/3 "2025-07-12T14:17:36Z")

</div>

I’ve just answered his first post about this (indirectly). I wrote _and documented_ the library, Trystan used my example sketches to write the default ones.

---

<div class="post-metadata">

**Author:** ![macrowe777](https://community.openenergymonitor.org/letter_avatar_proxy/v4/letter/m/4da419/32.png) [@macrowe777](https://community.openenergymonitor.org/u/macrowe777)\
**Post date:** [12 July 2025 15:39 UTC](https://community.openenergymonitor.org/t/node-id-for-emontx5-with-expansion-board/28836/4 "2025-07-12T15:39:01Z")

</div>

Cheers for the pointer