IND.I/O D21G with Keyence EM-030 Limit Switch

I am trying to read the status of a Keyence EM-030 inductive limit switch with an Industruino IND.I/O D21G. I am having some trouble because the NPN output of the limit switch is between 0 and 5V, at best. As this voltage does not get above the 11V threshold I am not able to detect this voltage fluctuation.

Does anyone have any ideas how I can get this to work?

Cameron Devine
Cameron Devine
| 1 1 1
Asked on 5/1/19, 10:20 PM

Hi, from the datasheet i see that it is an NPN type sensor, NO (normally open), powered by 10.8 to 30V. This means the active state of the sensor will connect its output to GND.

So we can use inverted logic: put a pull-up resistor (e.g. 1K or less) from the INDIO's V+ to the INDIO's Channel 1, this will pull the channel HIGH in the normal (NO) state of the sensor. Now connect the sensor's output to the INDIO's Channel 1 as well. When the sensor is activated, the Channel 1 should go LOW.

You can use below sketch to test, please let us know how it goes.

#include <Indio.h>
#include <Wire.h>

void setup() {
   Indio.digitalMode(1, OUTPUT); // Set CH1 as an output
   Indio.digitalWrite(1, LOW);   // clear CH1 to LOW
   Indio.digitalMode(1, INPUT);  // Set CH1 as an input
  pinMode(26, OUTPUT);   // LCD backlight

void loop() {
  digitalWrite(26, Indio.digitalRead(1));

| 1 1 3
Answered on 5/2/19, 3:56 AM

the value of the pull-up resistor depends on your supply voltage; if you use 24V you'd better use a higher value resistor e.g. up to 4.7K to limit the current, then a 1/4W resistor will do.

on 5/3/19, 7:11 AM

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Asked: 5/1/19, 10:20 PM
Seen: 1546 times
Last updated: 5/2/19, 3:56 AM