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   :sync_target: ../../zh_TW/nycu_notes/hardware_notes/2026_01_29_JST_EH_wrong_wiring.rst
   :sync_hash: caf7213519c96c727b407b2c38673daf505409ba


.. _2026_01_29_JST_EH_wrong_wiring_en:


2026-01-29 JST-EH Extension Cable Wiring Fix
============================================

.. warning::
   This page is translated by LLM and may contain some inaccuracies.
   `中文版 (Chinese Version) <../../zh_TW/nycu_notes/hardware_notes/2026_01_29_JST_EH_wrong_wiring.html>`_

This document records the process of fixing the JST-EH extension cable wiring error on 2026/01/23.


Background
----------

The official BOM requires us to purchase JST-EH Cables and Housings. However, spending around 40 TWD for a single 3-pin JST-EH extension cable is not cost-effective, so I tried purchasing `pre-crimped wires <https://item.taobao.com/item.htm?spm=tbpc.boughtlist.suborder_itemtitle.1.4f042e8dWKZ1rw&id=836918236262&mi_id=0000tZcB8VwUKXtTJHIoAc6yD3BiWi1BaVFyF69piPlywUY>`_.


.. raw:: html

    <div style="display: flex; flex-flow: row wrap; justify-content: space-around;">
        <img src="../../_static/jst_eh_back.jpg" style="flex: 15em; width: 15em;">
        <img src="../../_static/jst_eh_front.jpg" style="flex: 15em; width: 15em;">
    </div>

However, as shown in the image, if we name the pins 1, 2, and 3, there are theoretically two ways to connect them. Unfortunately, we bought the 1-3' 2-2' 3-1' type, but Dynamixel requires 1-1' 2-2' 3-3'.


Solution
--------

If you don't want to repurchase, you have to find a way to back out pins 1 & 3 from one end and re-insert them correctly. Here is our method—I was sitting on the floor at the time, but you might find a more elegant way.

1.  Hold the plastic connector housing on one end.
2.  Step on the wire connected to pin 3 to fix it (or secure it in another way), leaving the other two loose.

3.  Pull the plastic housing towards you while gently prying the rightmost plastic tab with a flathead screwdriver.

    *   Be careful not to use too much force, or the plastic might deform, affecting its ability to lock the terminal again.
    *   If successful, you can pull the wire out along with the metal terminal.

4.  Do the same for pin 1.
5.  Insert the wires back in the correct order. Ta-da! Done!

.. dropdown:: Contribution Log

    *   Operator & Author: Kevin Pan (@XiaoPanPanKevinPan)