Switch help

[nelson.ke@]

So we are looking at a wheel that rotates and then hits a switch and stopping. Then a button or trigger is pressed and activates the motor to rotate one revolution to the switch and stopped by the switch. Thus the mechanism is loaded for the next shot. [IMG][url=http://s857.photobucket.com/user/Thanousay_Khamphoune/media/Switchexample_zpse97584df.png.html]

[Ether]

Originally Posted by nelson.ke@

So we are looking at a wheel that rotates and then hits a switch and stopping. Then a button or trigger is pressed and activates the motor to rotate one revolution to the switch and stopped by the switch. Thus the mechanism is loaded for the next shot. [IMG][url=http://s857.photobucket.com/user/Thanousay_Khamphoune/media/Switchexample_zpse97584df.png.html]

Are you asking a question, or just sharing?

[nelson.ke@]

asking a question on how should I program that and maybe some pics of what teleop would look like. I want the motor to keep rotating until it hits the switch and then stop, a trigger on the controller would activate the cycle again so the motor goes around until it hits the switch again.

[Ether]

Originally Posted by nelson.ke@

asking a question on how should I program that and maybe some pics of what teleop would look like. I want the motor to keep rotating until it hits the switch and then stop, a trigger on the controller would activate the cycle again so the motor goes around until it hits the switch again.

How fast will this be rotating? Do you want it to reverse direction when the trigger activates the cycle, or continue on "through" the switch one complete rev?

What motor controller will you be using?

[Alan Anderson]

Do you want it to stop at the switch even if the operator is still pressing the button, requiring the button to be released first and then pressed again in order to start another cycle? Or do you want the motor to run continuously if the button is held down?

[nelson.ke@]

@Ether, we would like to continue through and use a talon as a motor controller

@Alan Anderson yes we would like the first option with the switch stopping the motor and then you have to release the trigger and press the trigger again to start the cycle.

Thanks!

[Alan Anderson]

Originally Posted by nelson.ke@

...we would like the first option with the switch stopping the motor and then you have to release the trigger and press the trigger again to start the cycle.

That's going to involve something a little more complicated than simple combinatorial logic. I suggest implementing it as a flat sequence in Periodic Tasks.

In the first frame, halt the motor and wait for the trigger to be released. In the second frame, halt the motor and wait for the trigger to be pressed. In the third, set the motor to whatever value you want it to run at and wait for the limit switch to be activated. Put the entire sequence in a neverending while loop so it starts over every time it finishes.

The "wait for" parts can be programmed as while loops that terminate when the condition is seen. Make sure to put a delay inside each of those loops so they don't monopolize the cRIO's CPU.

If this isn't enough to start with, let me know and I'll give you some example code to look at.

[nelson.ke@]

Originally Posted by Alan Anderson

That's going to involve something a little more complicated than simple combinatorial logic. I suggest implementing it as a flat sequence in Periodic Tasks.

In the first frame, halt the motor and wait for the trigger to be released. In the second frame, halt the motor and wait for the trigger to be pressed. In the third, set the motor to whatever value you want it to run at and wait for the limit switch to be activated. Put the entire sequence in a neverending while loop so it starts over every time it finishes.

The "wait for" parts can be programmed as while loops that terminate when the condition is seen. Make sure to put a delay inside each of those loops so they don't monopolize the cRIO's CPU.

If this isn't enough to start with, let me know and I'll give you some example code to look at.

I know only a little about labview, so I found the while loops and flat sequences and understand what you're saying. However, I'm not understanding how to program it. Can you send a pick of what you would do, like a pic of the program?

Thanks!

[Racer26]

Sure sounds to me like a snail cam based shooter mechanism with a limit switch for the 'cocked' position.

The pseudo-code for what you're looking for looks a little something like this:

if(camLoadedSwitch = on){
camMotor.setSpeed(0);
}

if(oldTriggerState = off AND currentTriggerState = on){
camMotor.setSpeed(1);
}
oldTriggerState = currentTriggerState;

That would start the motor on a rising edge of the trigger, and stop it when it hits the limit switch, assuming this code is in a function that's called periodically.

[Alan Anderson]

I won't be near a computer with this year's installation of LabVIEW on it until later today. I'll be able to post a snippet of code implementing what I described tonight.

[brycen66]

I would recommend using a Hall sensor as opposed to a physical limit switch. My team has had experiences with limit switches failing before. You can get a good cheap sensor kit at west coast products http://www.wcproducts.net/hall-effect/.

[Alan Anderson]

I attached a VI snippet of the sort of thing I was talking about. It goes in Periodic Tasks as its own loop, not inside anything else.

It will not work in its current form. Both of the limit switch while loops are configured to continue while the switch value is true. Depending on whether the switch is normally open or normally closed, one or the other of the loops needs to be changed to terminate when the switch value is true instead.

You will also need to use the appropriate Refnum names on the left side, and set the motor output to the proper value to make it run in the direction and at the speed you want.