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Back stop control and motor speed control help programming 
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Joined: Tue Feb 10, 2015 10:46 am
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Post Back stop control and motor speed control help programming
My kids are competing in the Science Olympiad and built a front end loader to pickup items and dump them in a cutoff milk jug. The issue is the arm that lifts comes down way too fast and does not stop, but coasts to a stop. We were told if we buy 393 Integrated Controllers, we should be able to tell it to apply reverse power or stop it as soon as they release the button to have it go down. Somehow it tracks the revolutions and then I am guessing if the button is not being pressed up or down it applies opposite power. We are looking for a helping hand to get at least a base code setup so we can then work from it as I have never programmed in Robotc or worked with a Robot. I do have programming experience years ago, so not totally a novice.

Also, we would appreciate a leg up on telling the two motors we using to propel the vehicle to spin slow like half speed when we push on the joystick levers. It is just two fast and touchy.

As far as the configuration is concerned, the kids are using two buttons on either side on the back of the controller to lift the arm up and down and then the other tilt the bucket. The motors that propel the vehicle are hooked up to the joysticks so they have been fine control.

Thanks for any help anyone can give.


Tue Feb 10, 2015 11:41 am
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Joined: Thu Dec 01, 2011 12:07 am
Posts: 151
Post Re: Back stop control and motor speed control help programmi
Please consider posting your current code to better support comments.


Tue Feb 10, 2015 12:43 pm
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Joined: Tue Feb 10, 2015 10:46 am
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Post Re: Back stop control and motor speed control help programmi
I am afraid we do not have any base code to start from and is part of our request. We would love to see some code that might cover these items and be able to modify it to try and make it work. We don't know where to start truly. We saw this link http://content.vexrobotics.com/docs/inv ... T-0112.pdf , but it does not give you much to go for programming it to help with the back power. Again, we are trying to stop the arm from going down immediately when the button to go down is let go. I understand the old 269 motors worked that way, but the new 393 (we have these) allow for the gravity and motion to cause the arm to continue in the direction downward coasting to a stop instead of immediately stopping. In our case, that means the arm moves 2-3 inches after we stop pressing the button. Also, code around telling the motors driving the wheels to go at half speed when the joystick is press forward or back instead of full power.

Any help would be appreciated.


Wed Feb 11, 2015 7:08 pm
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Joined: Thu Dec 01, 2011 12:07 am
Posts: 151
Post Re: Back stop control and motor speed control help programmi
Are you running the default code that comes with the cortex?
Do you have the RobotC software?
Start off by going to the motor and sensor setup and configuring your hardware in RobotC.
Then post the code so we understand what motors and sensors you have and how you labeled them.
There are examples in RobotC and a help system to learn individual commands.


Thu Feb 12, 2015 12:02 am
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Joined: Tue Feb 10, 2015 10:46 am
Posts: 4
Post Re: Back stop control and motor speed control help programmi
We are just now getting RobotC setup. We will try and configure the motors to half power and look at something called PID control on a motor to setup that we are reading in the http://www.robotc.net/forums/viewtopic.php?f=52&t=3774 post on Continuous Braking. If you happen to have time to read that post and see if we are all talking about similar things, that would be helpful. The post mentioned braking against gravity because the 393 motor is a continuous rotation servo versus the old 269 which were not. The arm has a weight on it and is driving it down.

Once we do our first download, we will get the code and post it. We are kind of against a deadline of a competition on Saturday, so I apologize for the frequent posts and request for assistance; at least you know why.


Thu Feb 12, 2015 11:14 am
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