Zumo Reflectance Sensor Array not working

Firstly I’d like to say that I have scoured the forums for a similar problem, but haven’t been able to find any; so I apologise if a new topic wasn’t necessary.

I am building a Zumo line following robot for the first time and I seem to be having problems reading values from the line sensor array.

I am using the standard Zumo v1.2 kit with an Uno R3 and Zumo reflectance array. I have followed the assembly instructions available on your website with the following differences:

  • Charge connector and buzzer have not been installed.
  • Vin pin on the Zumo has NOT been soldered in as I want the Arduino to be powered separately
  • I have NOT installed the 3 pin header on the array as my project does not need dynamic control of the LEDs/emitters.

I am using the basic calibration example code provided when the library is installed and these are the sensor values I get:

2000 2000 8 8 2000 40
2000 2000 8 8 2000 2000

As you can see Sensor 5 is the only one that works as it should. Changing the lighting conditions causes Sensor 1 and 4 to work intermittently. Sensor 2 sometimes gives values of ~100 min and ~140 max; again depending on the lighting conditions. But Sensors 0 and 3 never move from the values shown above.

It’s just odd that Sensor 5 consistently works well in all lighting conditions.

  • The sensor bar is about 5mm off the ground.
  • Using a phone I can tell that all 6 sensors give a purple glow.
  • The 2 red LEDs on the sensor bar are on.
  • The soldering was done by a professional solderer so there aren’t any solder joint issues.
  • I have confirmed continuity from the sensor pins all the way to the Arduino.
  • I am using black electrical tape on a white paper for calibration

I am afraid I am missing something very trivial. I appreciate any assistance as it is really frustrating.


I am having this exact same issue and was wondering if anyone has any more ideas?

I am using the Zumo robot kit with the v1.2 Shield and the onboard L3G gyro. I am using an UnoR3 and have assembled it according to the instructions on this website, so it is connected directly using header pins. I have not connected the buzzer however.

I am getting ~4V on SDA and ~1.4V on the SCL pins.

I am using the sample code provided with the library, so I can’t understand why it doesn’t seem to get past the (!gyro.init() part…

I am sorry you are getting behavior you do not expect from your sensor array and gyro. I noticed you posted in multiple places about issues with your Zumo, so I combined the unanswered posts in this thread, since the issues might be related.

Can you tell me more basic information about your setup? Can you verify that you are using fresh or newly charged batteries? How are you changing your lighting? Can you get any of the more basic examples working (e.g. ZumoMotorExample.ino)? Also, can you send pictures of your UNO mounted atop your Zumo and a video of your calibration process?


As per my post in the other thread: Zumo Shield power problem I think I may have resolved this problem.

I swapped the Shield with another one and the sensor problem seems to have been fixed. One of the 6 emitters on the bar still does not work, but atleast the other 5 work as they should.

I had swapped out the sensor bar and Arduino with another one but it didn’t fix it. So I thought I’d try swapping out the Shield itself and it seemed to do the trick.

Unfortunately I could not test out the L3G gyro as the Shield I used was an older version that does not have the onboard gyro. When I do get the 1.2 version I will test it out and let you know.

But yes, it does seem like all those problems are related. Cheers.

I am glad things are working now; thanks for posting what you did.