analogRead thrown off by digital PINs

Other Hardware Sensors
1

Hi everyone!
This is my first time on the forum.

I'm trying to read data from an Accelerometer (ADXL337 3 Axis Accelerometer with Analog Outputs)
while simultaneously blinking an LED.

I have two separate sketches doing both tasks successfull. But when I merged them, the analogRead() function that I use to get data from the Accelerometer started picking up voltage from the blinking LED.
This could be clearly seen in my plot of the dat (Using the Serial Plotter function in the IDE)

The blink function of the LED is controlled throw a switch. I have attached to screenshots of the accelerometer working with the LED blink function OFF(Filename:Normal_ADXL_output) and with the LED blink function ON(Filename:faulty_ADXL_output).

Is there a way to solve this? I tried adding a delay between my analogReads and that did not improve the situation at all.
I also tried reading the same pin twice to see if that would help and it did not.

I believe this is a known issue but I couldn't find much discussion on it or solutions.

Board is an Arduino Uno
LED is on pin 10 and 11
Analog read is done on PINs A0, A1 and A2

Any suggestions are appreciated

PS: It's great to finally join in on the conversation!

faulty_ADXL_output.PNG
faulty_ADXL_output.PNG962×1084 36.4 KB

Normal_ADXL_output.PNG
Normal_ADXL_output.PNG959×1085 17.1 KB

2

Your LED is pulling enough current to affect the 5V rail and thus show up on the analog readings I think.

You need to describe your hardware in more detail - what LED, what series resistor (do you even have one?), how long are the cables
to the accelerometer, are you sharing ground and supply wires to the accelerometer with the LED? A photo of
the setup can be useful.

Normally its important to separate supply and ground for a sensor from those to any high current loads, to prevent
this exact issue.