mBot problems


Hi all

My doughter got this mbot last christmas. It hasnt been used much since. But now my doughter started to get interested and we started to use it.
We found some very disturbing issues out of the box.
Its not going in a straight line, going slightly to the left.
The obsticle sensor does not work at all.
We tried to upgrade the software in the PC software version 5.* and the colour scheme got removed and also the remote stopped working.
Installed the PC software version 3.* and restored the unit back to factory mode. Colour scheme back, remote back but still same problem with not going straight and sensors not working again.
Please help me with this issues in a step by step fix. We are not engineers here. And not english speaking either as you guys might notice :blush:
Please help us

  1. Does the little LED on the ultrasonic sensor (= obstacle sensor) glow red? If yes … is it connected to the right port (check the manual)?

  2. Concerning running straight: I use 6 mBots and 2 had this issue as well. The root cause is that the mBot does not know how much the wheels turned. That’s one of the things which makes the mBot 4x cheaper than a Lego EV3.
    If one motor is a bit stronger than the other, then the mBot does not go in a straight line. You can try to fix by checking if the screws in the wheel are tightened equally. You can also try to order 1 or 2 replacement motors (they are not expensive) - propably you will then have a combination which works.

Concerning the default program which is only available in version 3: I noticed this too. @tech_support might have a statement on that.


Hello Stina,
Sorry for the delay.

  1. As the straight line, I am afraid that is not 100% guaranteed as the motor installation factor. Usually how much it deviates when runs 100cm?
  2. I have sent you a guidance on how to test the ultrasonic sensor, please test it and give me testing result with video;
  3. In mBlock 5, the first firmware is online firmware, but actually to get the default modes work including ir mode, we need to select the second firmware: default program. Also I sent guidance on troubleshooting IR controlling fails to work.
    More guidance on mBot and other products, please visit: Makeblock products resources download center

I am not quite sure “color scheme”, and “remote” refers to IR control?


Hi Andreas.

Yes it glows red and its connected to the right port. Double and tripple checked. :slight_smile:

  1. Ok, i can understand and accept that. Its not an servo like Moog :slight_smile:
  2. Where is it ? Cant find it.
  3. Can only find one firmware ?

  1. I sent the guidance again via email.
  2. here are two options when update firmware:


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