Obstruction detection doesn't work

#1

Hi,
My son has been going through the tutorial in the mBlock app (Android) in a new mBot and gets stuck at the obstruction detection which doesn’t seem to be working. I searched and came across this discussion:


It seems I have the same problem (red light, constant 400 reading regardless of port connected). What is the solution please? The thread is closed so I couldn’t reply there, hence I opened this one.
Thanks

#2

Hello Markosp,
If it always shows 400, it may be faulty. But kindly suggest you to upgrade firmware and then test it again. Try different cables, different ports to test again.
By the way, where and when did you purchase the mBot?

#3

Hi, thanks, I will try all these, most likely in the weekend.
I bought it on eBay, new (sealed).

#4

Hi, I updated the firmware and tried different cable and all the ports, still 400 all the time. :frowning:
What should I do now?

#5

Well, I am afraid that ultrasonic module is defective. Please turn to the shopper (Ebay) for replacement.

#6

Hello,
I replaced the ultrasonic sensor. The new one changes values so I assume it’s not faulty.
However, it doesn’t behave as I would expect it.
We are having a hard time working through the tutorial, where we need to tell the mbot to move until an obstacle is detected. Since the sensor is at the back of the mbot, it basically keeps going as the distance is bigger than what would be for an obstacle way ahead. I managed to make it move past that part of the tutorial by waving my hand around the sensor, but that surely isn’t supposed to be the solution.
Then same thing in the next one (5-7). The mbot is supposed to move forward and turn when it finds an obstacle. However the obstacle is not detected, it keeps bashing on things and not stopping/turning until I wave my hand over the ultrasonic sensor in the back.
What are we doing wrong please?
Edit: Here’s a video showing what I’m describing:
https://photos.app.goo.gl/x5hvjQXX6osVgS81A

#7

Please test it again in another place. The obstacle should be in front of the mBot then it will turn right.

#8

I did, it finally works, thank you.
It’s not perfect in that the obstacle has to be directly in front of it. For example if you program it to keep going forward until it finds an obstacle in which case it turns left (so it keeps going all the time Roomba style), it works if it goes towards walls but it doesn’t if there’s a chair leg ahead a bit off center. In that case the mbot hits the chair leg and gets stuck there as it doesn’t see the obstacle.
It’s still pretty good but I do wonder if it’s supposed to be that way.

#9

Glad to hear that. The ultrasonic sensor module has its detection angle, then it may cause that sometimes it is not very sensitive if the obstacle is not just front of it.

#10

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