Detecting presence of LED within Arduino

I had a need to detect whether a device was properly plugged in to an Arduino microcontroller.  My “proof of concept” test was to be able to see if I could come up with a way to have the Arduino tell me if an LED was plugged into a particular pin.

Here is what I found:

By modifying the ReadAnalogVoltage example, I was able to measure the voltage dropped triggered by the draw of the LED.

Here is the sketch:

Reads an analog input on pin 0, converts it to voltage, and prints the result to the serial monitor.
Attach the center pin of a potentiometer to pin A0, and the outside pins to +5V and ground.

This example code is in the public domain.

// the setup routine runs once when you press reset:
void setup() {
// initialize serial communication at 9600 bits per second:
pinMode(A0, OUTPUT);
digitalWrite(A0, HIGH);


// the loop routine runs over and over again forever:
void loop() {
// read the input on analog pin 0:
int sensorValue = analogRead(A0);
// Convert the analog reading (which goes from 0 – 1023) to a voltage (0 – 5V):
float voltage = sensorValue * (5.0 / 1023.0);
// print out the value you read:


When I place an LED across pins A0 and GND, the serial output goes from 5.00 down to 4.09.

A little bit of application specific programming and think this will do quite nicely as a means to detect if a device is properly connected to the Arduino microcontroller.


Arduino Digital Read Out

I recently had opportunity to resurrect my Harbor Freight X2 Mini Mill CNC conversion.  I had previously installed a digital read out (DRO) by using the cheap “chinese” scales and the Yadro software.

The Yadro software worked well, but required a DOS PC to run it on.  Thinking there might be a better option out out their in late 2013, not wanting to dedicate an entire PC to such a simple task, and error codes coming from my dusted off Yadro board led me to a fire off a quick google search.

I stumbled upon Yuriy’s “Do It Yourself DRO Project“.  It’s a beautiful concept, employing an Arduino Uno, a handful of components and an Android tablet as the display.  I imagine I have enough components in my parts drawer to assemble it.  And it will give me a use for the Ollie’s special Android tablet I have sitting around.

Stay tuned for a new post, while I venture off on another new build.