Zumo robot line follower, wall follower and obstacle avoider

Hello there,
So, i am planning to use the Zumo robot in a national competition that features an-all terrain track. The lower region basically has a line following zone, shouldn’t be a problem for the zumo.
The upper region features wall following and obstacle avoiding. So, what do you suggest, using one ultrasonic sensor at the side for wall following will be fine. For the obstacle avoidance zone? one HC-SR04 mounted on a rotating servo? or 3 HC-SR04s mounted in three directions in stationary configuration? what do you guys suggest?
Also, this track has a lot of inclinations with the most difficult one at a 34 degree rugged terrain inclination. Which motor do you suggest for the zumo? Around how much torque will i require? I also need speed so am i fine with the 50:1 HP motor version? Does the zumo have the kick in it?
And, i am really not considering the rover 5, a good option, but the zumo is a lot quicker, i pretty much want to stick to the zumo. I am planning to buy a non-assembled kit version, i really hope i don’t run out of pins. So, will i have enough pins for around 3 HC-SR04s and one zumo array?
That would mean 6 digital I/O pins for the HC-SR04 and 6 I/O pins for the array? Do you suggest me the UNO or Leonardo?
More info on the competition here :https://www.dropbox.com/s/674qpf4iezfreq2/mission%20nepal.pdf
Thanks, would be great to hear your opinions and ideas :smiley:


Having multiple fixed sensors is probably easier, but a single panning sensor might be more interesting. You should use the approach you feel more comfortable with.

As for your motor choice, I do not know for certain, but I suspect the 50:1 HP motors will have plenty of torque. I expect that the limitation for climbing an incline is more likely to be traction of the treads and not torque of the motors.

There are 10 pins on the front expansion (using the compass will take up two of these) and 2 you can use if you do not use the buzzer. If you are worried that you will need more pins, you could reduce the number of sensors used on the on the line sensing array. Alternatively, you could try combining the trigger wires for all three of your HC-SR04 sensors. You might also consider using our analog Sharp distance sensors as each one requires only one analog input pin:


The Sharp sensors are probably easier to use and should provide more than sufficient range compared to the size of the Zumo.

In regards to whether you should use the Arduino UNO or Arduino Leonardo, both will work with the Zumo, and you should use the one you feel more comfortable using.

- Grant

Thanks for the suggestion.
I don’t think i will go over the big incline there, but do you think the zumo can handle the smaller inclines? Is there a possibility that it might flip over considering its short length of just 9cm? Could you, if somehow, conduct a simple experiment with the zumo in inclines, or maybe you have already conducted such tests? And maybe possibly share with me the results? It does have good speed, but i fear that it might flip over due to its short length.
The inclines on my track range from 17 degrees to max 37degrees. is a test possible over there at the pololu labs? I would be really grateful.
Also, what have you used to mount the sharp digital sensors on the round plate chasis? i know that there is a mounting hole but how did you manage to mount it vertically? It look well-fitted on the chasis board.

And one more thing. If i buy the pre-assembled version of the zumo, the zumo array is completely soldered into the zumo shield. So it uses pins 5, 4, A2, A3, A0, 11 by default, right? That means i can use pins 2, A1, A4 and A5 for other sensors? or would that require certain modification? I know that i can make a cutoff as well to open up room for pins by using less on the array. So, 10 max. I/O pins that can be used on the zumo? Or please tell me how i can get the max possible no. of I/O pins? I really don’t require much use of the buzzer, compass and the accelerometer in this project, i’ll make use of them later. This time, i plan on using 4-5 sharp digital distance sensors at the front for obstacle avoidance, and a sharp analog distance sensor at the side for wall following, and the array for line following ( fast line following) what do you suggest?

Thank you so much for your time


The amount of incline the Zumo can climb is dependent on the amount of traction the tracks can get. This is affected by a variety of factors, for example the material of the surface and how clean it is. Please note, the assembled Zumo comes with the 75:1 HP micro metal gearmotors, which will have more torque than the 50:1 HP gearmotors. In regards to the Zumo tipping over, we designed it to have low center of gravity, but that will change when you add the sensors and make other modifications. If the robot gets top-heavy, it is more likely to tip over; this is something you will have to determine once you have modified the Zumo.

You also ask about mounting the sensors to a “round plate chassis”. Could you tell me what chassis this is and provide a link?

If you buy the Zumo assembled, it is correct that the sensor array will use pins (4, 5, A0, A2, and A3). Leaving the other four pins you mention (2, A1, A4, and A5) and the two from the buzzer (3 and 6) available for use. This should give you a total of 12 pins you can use for peripherals.

- Grant