Robot won't move forward

Hi, we are brand new to VEX and started out by building the claw bot. When attempting to drive forward using the controller, it either lurches and stops abruptly or doesn’t move at all. This happened straight out of the box, prior to any firmware updates or programming. It will drive straight backwards, and curve backwards, but not forward at all. Sometimes it moves on its own too, which is very odd. :slight_smile: Batteries are fully charged. Is this some sort of calibration issue, or do we have a bad brain?

There is a calibration process on the brain. You’ll need to connect the controller to the brain, again.

Have you got any sensors plugged in? The distance sensor could be preventing you driving forwards and the gyro could be making it move on it’s own - the default driver control program has some demo functionality for these sensors built in. If you have these sensors connected, unplug them with the brain switched off, turn the brain on and try again.

As Steve says, the creeping could also be a joystick calibration issue.

Thanks for your replies. We did go through calibration with the brain. The forward motor works properly with the controller when running our own custom program. It does not work properly when running the “Driver Control” program. (Pre-loaded on the brain)

Do you have any sensors plugged in? As per my previous post, these will affect the behaviour of the built-in Driver Control program.


Ahh, I missed that earlier. That was the problem, Chris. My son had built the clawbot following the instructions, which include adding sensors. We unplugged the sensors and it drives fine now. Thank you! So when students compete in the driver control portion, do they write their own driver control program, or do they unplug their sensors and use the built in program?

Brilliant, glad that you have got it sorted.
Generally for competition, students write their own programs. More than anything else, the robots that they design specifically for the challenges would have different motor configurations to the standard Clawbot/Ike etc. so you would need to create a program to configure everything to your requirements anyway.

Hey calvc01, I unplugged my distance sensor and then replugged it and now my clawbot is moving forwards and backwards again. Now I have a question, why did plugging and unplugging the distance sensor work? Thanks!

Did you unplug it and re-plug it whist is was switched on? VEX IQ doesn’t support “hot-swapping” at the moment which means you can’t plug in a sensor whilst the brain is on, it just won’t see it until you restart the brain. Therefore, maybe it just stopped seeing it until you rebooted.
By the way, something else important to remember is that this problem only affects the old style firmware up to version 1.16. If you are now using the VEXos update this problem won’t exist anymore because the new Driver Control default on VEXos doesn’t use the sensors at all.
To check what version you have, go to Settings and then Device Info on the brain - v2.0.1 or above = VEXos

You can easily see if you are using VEXos because the second item on the menu of the brain will be “Demos” - you can find a version of Driver Control that does use sensors under this option.

Yup, I unplugged, turned off the brain, turned on the brain, and then replugged it again. I have two machines. One I had to disconnect the distance sensor and the other one I had to disconnect the gyro sensor and then the distance sensor. They now both work. What is the default setting of the sensors anyway? Why when they are connected do they stop the clawbots from driving forward?

I looked at the System Info on the brain and it says v 1.15. I will now try to update the VEXos to 2.0.1

So I upgraded to 2.0.1. and now it’s working like a charm :slight_smile: Thanks, calvc01

To anyone else reading this, it’s very easy. Just go to the VEX IQ website, download the VEXosUtility, plug in your controller and all your sensors, open the VEXosUtility, wait for a couple of minutes and then press Install :slight_smile:

Thread resurrection, one year later…

The robot claw would only move up or down in one direction when my students made their Clawbot today. I noticed that the claw was hitting the bumper and so it seems that it would shut the claw down, so I detached the bumper from the brain, and the claw would go up and down again.

The brain has code in it to stop motor movement when it’s pressed. Look at the brain guide that came with your robot.