<?xml version="1.0" encoding="UTF-8"?>
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        <title>Proximity Sensor problems</title>
        <description> I&#039;ve been struggling with this for a while.... 

I converted my wanhao duplicator i3 over to ramps and Marlin about 6 months ago. I used a proximity sensor and all was good. 

I decided to upgrade to TMC2100 drivers. They were noisy on 12v so bought a 24v PSU and a MKS Gen 1.4 board. 

I can get everything working except the prox sensor. 

Its a LJ18A3-8-Z/BX NPN (NO I think).

I built a voltage divider that drops the 24v down to about 4.4v for the z-min pin (pic attached).

When I dont have the z-min lead connected I read about 4v when the sensor isn&#039;t detecting, and down in the millivolts when it does. 

I&#039;ve disabled the auto bed levelling for now. Hopefully this will make it simpler to test. 

configuration_h attached.
 
Thanks in advance!! 

//===========================================================================
//============================== Endstop Settings ===========================
//===========================================================================

// @section homing

// Specify here all the endstop connectors that are connected to any endstop or probe.
// Almost all printers will be using one per axis. Probes will use one or more of the
// extra connectors. Leave undefined any used for non-endstop and non-probe purposes.
#define USE_XMIN_PLUG
#define USE_YMIN_PLUG
#define USE_ZMIN_PLUG
//#define USE_XMAX_PLUG
//#define USE_YMAX_PLUG
//#define USE_ZMAX_PLUG
// coarse Endstop Settings
//#define ENDSTOPPULLUPS // Comment this out (using // at the start of the line) to disable the endstop pullup resistors

#if DISABLED(ENDSTOPPULLUPS)
  // fine endstop settings: Individual pullups. will be ignored if ENDSTOPPULLUPS is defined
  //#define ENDSTOPPULLUP_XMAX
  //#define ENDSTOPPULLUP_YMAX
  //#define ENDSTOPPULLUP_ZMAX
  #define ENDSTOPPULLUP_XMIN
  #define ENDSTOPPULLUP_YMIN
  //#define ENDSTOPPULLUP_ZMIN
  //#define ENDSTOPPULLUP_ZMIN_PROBE
#endif

// Mechanical endstop with COM to ground and NC to Signal uses &quot;false&quot; here (most common setup).
#define X_MIN_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define Y_MIN_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define Z_MIN_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define X_MAX_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define Y_MAX_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define Z_MAX_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define Z_MIN_PROBE_ENDSTOP_INVERTING true // set to true to invert the logic of the probe.

// Enable this feature if all enabled endstop pins are interrupt-capable.
// This will remove the need to poll the interrupt pins, saving many CPU cycles.
//#define ENDSTOP_INTERRUPTS_FEATURE


</description>
        <link>https://reprap.org/forum/read.php?415,812811,812811#msg-812811</link>
        <lastBuildDate>Thu, 16 Jul 2026 22:42:36 -0400</lastBuildDate>
        <generator>Phorum 5.2.23</generator>
        <item>
            <guid>https://reprap.org/forum/read.php?415,812811,812846#msg-812846</guid>
            <title>Re: Proximity Sensor problems</title>
            <link>https://reprap.org/forum/read.php?415,812811,812846#msg-812846</link>
            <description><![CDATA[ Perfect! that worked a treat.<br />
<br />
removed that r20 and it instantly started working. <br />
<br />
Thank you]]></description>
            <dc:creator>nick9one1</dc:creator>
            <category>Firmware - Marlin</category>
            <pubDate>Sun, 04 Mar 2018 04:55:34 -0500</pubDate>
        </item>
        <item>
            <guid>https://reprap.org/forum/read.php?415,812811,812843#msg-812843</guid>
            <title>Re: Proximity Sensor problems</title>
            <link>https://reprap.org/forum/read.php?415,812811,812843#msg-812843</link>
            <description><![CDATA[ The problem with mks 1.4 boards is that they have a 'physical' pullup resistior  (R"0 i think)  mounted on the board(near the endstop connector) so disabeling pullups in te config.h has no effect.<br />
You will likely need to remove this resistor for your sensor to work, or as i did, i replaced the resistor divider by a reverse biased diode.<br />
<br />
Here is a u-tube link to the reistor fix.<br />
<br />
[<a href="https://www.youtube.com/watch?v=Z506pBM4OEA" target="_blank"  rel="nofollow">www.youtube.com</a>]]]></description>
            <dc:creator>obewan</dc:creator>
            <category>Firmware - Marlin</category>
            <pubDate>Sun, 04 Mar 2018 04:13:07 -0500</pubDate>
        </item>
        <item>
            <guid>https://reprap.org/forum/read.php?415,812811,812811#msg-812811</guid>
            <title>Proximity Sensor problems</title>
            <link>https://reprap.org/forum/read.php?415,812811,812811#msg-812811</link>
            <description><![CDATA[ I've been struggling with this for a while.... <br />
<br />
I converted my wanhao duplicator i3 over to ramps and Marlin about 6 months ago. I used a proximity sensor and all was good. <br />
<br />
I decided to upgrade to TMC2100 drivers. They were noisy on 12v so bought a 24v PSU and a MKS Gen 1.4 board. <br />
<br />
I can get everything working except the prox sensor. <br />
<br />
Its a LJ18A3-8-Z/BX NPN (NO I think).<br />
<br />
I built a voltage divider that drops the 24v down to about 4.4v for the z-min pin (pic attached).<br />
<br />
When I dont have the z-min lead connected I read about 4v when the sensor isn't detecting, and down in the millivolts when it does. <br />
<br />
I've disabled the auto bed levelling for now. Hopefully this will make it simpler to test. <br />
<br />
configuration_h attached.<br />
 <br />
Thanks in advance!! <br />
<pre class="bbcode">
//===========================================================================
//============================== Endstop Settings ===========================
//===========================================================================

// @section homing

// Specify here all the endstop connectors that are connected to any endstop or probe.
// Almost all printers will be using one per axis. Probes will use one or more of the
// extra connectors. Leave undefined any used for non-endstop and non-probe purposes.
#define USE_XMIN_PLUG
#define USE_YMIN_PLUG
#define USE_ZMIN_PLUG
//#define USE_XMAX_PLUG
//#define USE_YMAX_PLUG
//#define USE_ZMAX_PLUG
// coarse Endstop Settings
//#define ENDSTOPPULLUPS // Comment this out (using // at the start of the line) to disable the endstop pullup resistors

#if DISABLED(ENDSTOPPULLUPS)
  // fine endstop settings: Individual pullups. will be ignored if ENDSTOPPULLUPS is defined
  //#define ENDSTOPPULLUP_XMAX
  //#define ENDSTOPPULLUP_YMAX
  //#define ENDSTOPPULLUP_ZMAX
  #define ENDSTOPPULLUP_XMIN
  #define ENDSTOPPULLUP_YMIN
  //#define ENDSTOPPULLUP_ZMIN
  //#define ENDSTOPPULLUP_ZMIN_PROBE
#endif

// Mechanical endstop with COM to ground and NC to Signal uses "false" here (most common setup).
#define X_MIN_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define Y_MIN_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define Z_MIN_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define X_MAX_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define Y_MAX_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define Z_MAX_ENDSTOP_INVERTING true // set to true to invert the logic of the endstop.
#define Z_MIN_PROBE_ENDSTOP_INVERTING true // set to true to invert the logic of the probe.

// Enable this feature if all enabled endstop pins are interrupt-capable.
// This will remove the need to poll the interrupt pins, saving many CPU cycles.
//#define ENDSTOP_INTERRUPTS_FEATURE


</pre>]]></description>
            <dc:creator>nick9one1</dc:creator>
            <category>Firmware - Marlin</category>
            <pubDate>Sat, 03 Mar 2018 18:41:30 -0500</pubDate>
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