Zumo Movement problem

Hi, I recently bought a second hand Zumo robot from Ebay for teaching robotics and programming with my Scout group. I seem to be having an issue with the Zumo turning. It starts turning properly, but about halfway through the turm, the track that would be turning in reverse to help generate the turn seems to loose power and with only the forward turning track going, quite often slows and stops.

Initially, I thought it was probably the motors were knackered. Then after doing a little testing, I think the motors are fine. If I hold the Zumo in my hand and add a little pressure to the track to try and slow them, they seem to have plently torque. As I turn the Zumo, something changes with the motors, when they swap direction of movement, they feel like there slipping or flicking quickly between forward and backword movement.

For info, it’s an original version Zumo with an Arduino Leonardo and I’m using the example sketches.

Also, is there a way to test the sensor array? I’m not 100% convinced by the previous owners soldering.



I am sorry you are having that issue with the Zumo. Can you tell me more about your setup? What speed values are you using in your example sketch? Can you post pictures of both the working and non-working treads and a video that clearly shows the behavior you are seeing?

As for your question about the sensor array, you test it by running the SensorCalibration sketch, which has code for reading the raw sensor values (you will have to uncomment some lines). That sketch is included in our Zumo-Shield library.


Hi, thanks for the reply.

Just after posting the forum post, I spotted the Sensor Array Calibration sketch (Doh!) Turns out my suspicions were correct about the previous owners soldering. Two of the sensors didn’t work due to badly soldered connections and after digging out my soldering iron, I got them running properly. :smiley:

Unfortunately, the ebay description doesn’t mention the gear ratios, so at present, I haven’t a clue! The SumoCollisionDetect sketch runs great, but when running the Compass sketch, it still doesn’t want to complete those turns (small turns are fine, big turns aren’t). The speed settings on the sketch haven’t been touched, they are the default settings. Being rather new to robotics I gather you need to tweak speed settings in the sketch depending on the gearing used? I’ll try emailing the original owner to see if he can shed some light on the gear ratio for the motors. I may still just play it safe and buy brand new motors.

Nice. I am glad you were able to get your array working properly!

We have not heard of people having that kind of issue with the Zumo motors unless they are running their motors on a low duty cycle, or their batteries are dying. So, it would be good if you could confirm the gear ratio used in your Zumo’s gearmotors. (We typically recommend people use the 50:1, 75:1, or 100:1 gear ratios.) Also, if you post a video that clearly shows the behavior and the treads, I might be able to see if there is anything else amiss in the system.