mBot motors running at different speeds

#1

Hi I bought the mBot to use in my class. I love the idea and we were having a good time with it. However, now the motors are running at different speeds and the robot goes in a big circle. Any ideas as to how I can fix this, or somehow work around it? I’d like to keep it but am not sure what to do.
thanks

#2

I’d ask that you post the code so we can see if there’s anything there.

What I’d suggest is:

  1. Go through the steps of Upgrade Firmware / Reset Default Program to flush out anything that might be causing a software issue.
  2. Make sure nothing is rubbing against the wheels as this frequently seems to be the cause of one wheel running slower than the other one.
  3. Make sure that you are using fully charged batteries.

If that doesn’t resolve the issue, I’d suggest dropping an email to support@makeblock.cc. :slightly_smiling:

#3

Thanks chuckmcknight,

I have upgraded the firmware, reset the default program, checked for rubbing and even rotated the wheels. I also put in new batteries. The right motor is still going much faster than the left. We are using the iPad app mBlocky rather than the PC version mBlock. So on the iPad there is no option for changing motor speeds for each motor. Right now I don’t know how to use mBlock. I’ve tried the tutorials but they do not really say too much. Basically, if I can not get both motors to operate at the same speed, the robot will be no good for grade 3 to 5 which is what we bought it for. Do you know of any link that would teach me how to incorporate different motor speeds in an mBlock program on the PC? Thanks

#4

Well, you can find the Makeblock tutorials for mBlock (which is based on Scratch 2.0) here and here. If you have no experience with Scratch, there are a number of tutorials available online at many locations (YouTube has many video tutorials as well).

There is a motor block in mBlock that can be set to affect a single motor (set motor (motor number) speed [power]), although my experience is that using the (run forward / run backward / turn left / turn right] at speed [power]) block to do the right thing.

I’m assuming that you’ve check the connections on the motors to ensure they are not loose.

It is always possible that you may have a defective motor, but these are fairly inexpensive motors and there is some variance in turning.

If you are running the motors under about 75, you may see this behavior as well. I can run my mBot at 70, but much below that and it won’t go at all.

The example below demonstrates both methods and lets the motors run for 2 seconds (the wait block).

#5