Can't solve mBot Blockly step 5-3


Hi there, we are stuck at the step 5-3 of the scratch learning program. The wait until block and obstacle ahead block. Mbots doesn’t stop nor does it recognized that there is a wall…



can you share a picture


Hi Spot1903,
Please check if you have the correct code.
Also please make sure the ultrasonic sensor is connected to port 3 and worked properly.



@tech_support I’m having the same problem. I’ve now tried troubleshooting steps outlined in the knowledge article. Check the connect on port 3 and the sense has a red light on. I’ve updated the firmware and the batteries are Duracell and brand new. The mBot is brand new as well purchased from Amazon last week.


Try changing the block to move backward. This may be a glitch. :confused: But please try it anyway @Tamarak. Good luck!


Thank you.

I gave this a try and the mBot would not stop moving backward even with an object planted in front of it.

I tried using my PC with the sensor test code mentioned here:

Got stuck pretty fast as the “say” option wasn’t available to me as outlined in the word document.


@Tamarak Hmm… Try uploading some test codes to the mBot to see if the sensors are all operating correctly.


@Tamarak @mesut @Spot1903 @everyone

Here is the correct code and the hint:

To use this code, please make sure that the ultrasonic sensor is plugged in to port 3, then place the mBot in an unobstructed area. Run the code, wait a second or so, and then move your hand in front of mBot’s sensor (about 3 inches (7.62 centimeters) away). The mBot should stop moving. I have no issues!