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-   -   Limit Swtich Help (http://www.chiefdelphi.com/forums/showthread.php?t=133983)

Ether 04-02-2015 22:49
Re: Limit Swtich Help
 
Quote:
Originally Posted by mmaunu (Post 1438538)
Ether: I have learned so much from reading your posts and papers over the years. I didn't intend to sound like I was correcting your post but merely adding explicit context for other readers.
Understood. The additional explanation you provided was appropriate and useful. Reps :-)

Jon Stratis 04-02-2015 22:58
Re: Limit Swtich Help
 
Quote:
Originally Posted by curtis0gj (Post 1438532)
I have setup the limit switch program with the suggestions but I am attempting to setup reverse for the victors. Also I am trying to setup the same if statement layout for my relays does this look okay?
Code:
public class Robot extends SampleRobot {
    RobotDrive robot;
    Joystick stick;
    Joystick xbox;
    Relay spike1;
    Relay spike2;
    Victor victor1;
    Victor victor2;
    DigitalInput limit;
    boolean limitPressed = false;

    public Robot() {
            robot = new RobotDrive(0, 1);
        stick = new Joystick(1);
        xbox = new Joystick(0);
        spike1 = new Relay(0);
        spike2 = new Relay(1);
        limit = new DigitalInput(4);
        victor1 = new Victor(4);
        victor2 = new Victor(5);
    }
    public void operatorControl() {
           
            while (isOperatorControl() && isEnabled()) {
            stick.getThrottle();
            robot.arcadeDrive(stick.getY(), stick.getX());
            limitPressed = limit.get(); //Do I want this out side of my while operator control loop?
            System.out.println("limitPressed=" + limitPressed); //Read the RoboRIO log for some values before you go all out on your motors.
           
            if(limitPressed) {
                    victor1.set(0);
                    victor2.set(0);
            } else if (xbox.getRawButton(4)) {
                    victor1.set(1);
                    victor2.set(1);
            } else {
                    victor1.set(0);
                    victor1.set(0);
            }
            if(xbox.getRawButton(1)) {
                    victor1.set(-1);
                    victor1.set(-1);
            } else {
                    victor1.set(0);
                    victor2.set(0);
            }
            if(xbox.getRawButton(3)) {
                    spike1.set(Relay.Value.kForward);
                    spike2.set(Relay.Value.kForward);
            } else {
                    spike1.set(Relay.Value.kOff);
                    spike2.set(Relay.Value.kOff);                   
            }
            if(xbox.getRawButton(2)) {
                    spike1.set(Relay.Value.kReverse);
                    spike2.set(Relay.Value.kReverse);       
            } else {
                    spike1.set(Relay.Value.kOff);
                    spike2.set(Relay.Value.kOff);
            }   
            }
    }
The relays look good. In addition to double victor1's which have already been pointed out, consider the effect of pushing buttons 1 and 4 at the same time - you'll oscillate between full speed forward and full speed reverse. It's probably not a big deal, as your driver shouldn't be pushing them both at the same time anyways, but I personally like to prevent that sort of situation. Using some fairly simple logic, you can reduce everything dealing with the victors to a single if/else-if/else block. Something like:
Code:
if ()//the conditions you want it to go up
{
    //go up
}
else if ()//the conditions you want it to go down
{
    //go down
}
else
{
    //stop
}
You can set up the conditionals using the AND (&&) operator, the OR (||) operator, and the not (!). For example, to say "when button 4 is pressed and the limit switch is not pressed", you would do "xbox.getRawButton(4) || !limitPressed". Figuring out how to use logic like this is a very powerful tool while programming!

mmaunu 04-02-2015 23:37
Re: Limit Swtich Help
 
Quote:
Originally Posted by Jon Stratis (Post 1438561)
For example, to say "when button 4 is pressed and the limit switch is not pressed", you would do "xbox.getRawButton(4) || !limitPressed". Figuring out how to use logic like this is a very powerful tool while programming!
Just to clarify for others, the condition would have && instead of ||:
Code:
    xbox.getRawButton(4) && !limitPressed
which is what you said very clearly but we all get noise in our signal sometimes between the brain and the fingers :)

Reps from Ether! I am showing my students that one!!! You might have a little bit of a fan club here at Team 2485...we seriously owe a lot to you and it is a shame if I haven't said that and "thank you" before (which is probably the case as I am mainly a lurker...but I am working on it).

curtis0gj 05-02-2015 06:32
Re: Limit Swtich Help
 
Quote:
Originally Posted by Jon Stratis (Post 1438561)
The relays look good. In addition to double victor1's which have already been pointed out, consider the effect of pushing buttons 1 and 4 at the same time - you'll oscillate between full speed forward and full speed reverse. It's probably not a big deal, as your driver shouldn't be pushing them both at the same time anyways, but I personally like to prevent that sort of situation. Using some fairly simple logic, you can reduce everything dealing with the victors to a single if/else-if/else block. Something like:
Code:
if ()//the conditions you want it to go up
{
    //go up
}
else if ()//the conditions you want it to go down
{
    //go down
}
else
{
    //stop
}
You can set up the conditionals using the AND (&&) operator, the OR (||) operator, and the not (!). For example, to say "when button 4 is pressed and the limit switch is not pressed", you would do "xbox.getRawButton(4) || !limitPressed". Figuring out how to use logic like this is a very powerful tool while programming!
So when I go to add my second limit switch for the top could I use if(limit || limit2) or do I need a new if statement? Also I have been trying to figure out how to covert my victor buttons to axis would this be the correct way,
if(xbox.getRawAxis(I need to check mapping)) {
victor 1.set(1);
victor2.set(1);
}

Jon Stratis 05-02-2015 07:52
Re: Limit Swtich Help
 
Good catch mmaunu... I can only blame Sleep deprivation from the build season :P

Curtis, that looks correct for dealing with two limit switches, good job!

If you want to control the victors with axis instead of buttons, you need to pay attention to what the return types are. A button returns a Boolean, true or false, as it only has two states (pressed or not pressed). An axis from a joystick, however, returns a number between -1 and 1, indicating how far it is moved from the center. Treating that number like a Boolean in an if statement won't do what you want. Instead, you have three options:

Option 1 - turn the number into a Boolean value by using a comparison. You can say something like "if(axis > 0)" to indicate that you want to do something if the value of the axis is positive. Other handy comparisons are less than (<), equals (previously discussed, ==), and not equals (!=).

Option 2 - use the axis to give you variable speed control over the motor. By passing the axis directly into the motor, something like "victor1.set(axis)", the motor will go at a speed proportional to how far you move the joy stick, and it'll go both up and done with that one command! Also, if you let go of the joystick, it'll stop

Option 3 - this is kind of a combination of options 1 and 2 by using something called a ternary operator. A ternary operator is kind of like doing an if statement in a single line. An example would be "axis>0?1:0;". You can read this as " if the axis is greater than 0, then use the value 1, otherwise use the value 0". Everything before the question mark is your conditional. Everything between the question mark and the colon is what happens if true, and everything after the colon is what happens when false. So, if we always want the elevator moving at full speed, we could do something like "victor1.set(axis>0?1:axis<0?-1:0);". Here I strung two ternary operators together - if the axis is greater than 0, return 1, otherwise if the axis is less than 0 return -1, otherwise return 0. Many people find ternary operators confusing and non-intuitive, so don't feel bad about going with a more straightforward option!

Finally, a word of warning. Often when you let go of a joystick, it will return to something very close to 0, but not quite there. In all the examples above, I used an absolute 0 value for comparisons, which won't work unless the joystick returns to be perfectly centered! It's a lot better to use a "deadband" around 0 - go up if it's greater than 0.05, go down if less than -0.05, otherwise stop. That way if the joystick is close to center you'll stop.

curtis0gj 05-02-2015 08:19
Re: Limit Swtich Help
 
Quote:
Originally Posted by Jon Stratis (Post 1438633)
Good catch mmaunu... I can only blame Sleep deprivation from the build season :P

Curtis, that looks correct for dealing with two limit switches, good job!

If you want to control the victors with axis instead of buttons, you need to pay attention to what the return types are. A button returns a Boolean, true or false, as it only has two states (pressed or not pressed). An axis from a joystick, however, returns a number between -1 and 1, indicating how far it is moved from the center. Treating that number like a Boolean in an if statement won't do what you want. Instead, you have three options:

Option 1 - turn the number into a Boolean value by using a comparison. You can say something like "if(axis > 0)" to indicate that you want to do something if the value of the axis is positive. Other handy comparisons are less than (<), equals (previously discussed, ==), and not equals (!=).

Option 2 - use the axis to give you variable speed control over the motor. By passing the axis directly into the motor, something like "victor1.set(axis)", the motor will go at a speed proportional to how far you move the joy stick, and it'll go both up and done with that one command! Also, if you let go of the joystick, it'll stop

Option 3 - this is kind of a combination of options 1 and 2 by using something called a ternary operator. A ternary operator is kind of like doing an if statement in a single line. An example would be "axis>0?1:0;". You can read this as " if the axis is greater than 0, then use the value 1, otherwise use the value 0". Everything before the question mark is your conditional. Everything between the question mark and the colon is what happens if true, and everything after the colon is what happens when false. So, if we always want the elevator moving at full speed, we could do something like "victor1.set(axis>0?1:axis<0?-1:0);". Here I strung two ternary operators together - if the axis is greater than 0, return 1, otherwise if the axis is less than 0 return -1, otherwise return 0. Many people find ternary operators confusing and non-intuitive, so don't feel bad about going with a more straightforward option!

Finally, a word of warning. Often when you let go of a joystick, it will return to something very close to 0, but not quite there. In all the examples above, I used an absolute 0 value for comparisons, which won't work unless the joystick returns to be perfectly centered! It's a lot better to use a "deadband" around 0 - go up if it's greater than 0.05, go down if less than -0.05, otherwise stop. That way if the joystick is close to center you'll stop.
So could I do something like
Code:

axis = Xbox.getRawAxis(someaxis); // Do I need float or double?

if(axis == 1) {
    victor1.set(1);
    victor2.set(1);
}
Sorry if thats way off Im still a bit confused.

Jon Stratis 05-02-2015 09:19
Re: Limit Swtich Help
 
Quote:
Originally Posted by curtis0gj (Post 1438644)
So could I do something like
Code:

axis = Xbox.getRawAxis(someaxis); // Do I need float or double?

if(axis == 1) {
    victor1.set(1);
    victor2.set(1);
}
Sorry if thats way off Im still a bit confused.
Your getting there! It can be hard to learn this stuff remotely without someone experienced there to help.

Your code is actually really close. Joystick axis values are returned as doubles, but that's a good question! There is often a lot of confusion between float and double, as they appear to be basically the same. In situations like thiszits useful to look at the javadoc For the object your using. A quick search turned up a copy here: http://team2168.org/javadoc/ go there and click on "Joystick" in the class listing on the left. You can then scroll through all of the methods in the joystick class, find the one you're using, get a short description of it, and see its return type. Pretty handy!

With the code you posted, the elevator will go up only if you have the joystick pushed full forward so the return value is 1. Pushing it halfway, so you get 0.5, wouldn't move it. Additionally, if you aren't pushing perfectly straight, you won't get a return value of 1! Take a piece of graph paper, draw a set of axis, and then draw a circle with a radius of 1, centered on the origin. Everything inside that circle is a value that can be returned by the joystick. If you push the joystick forward, you could get 0 for the x axis and 1 for the y axis... Or you could get something just a little less than 1 for the y axis and a little greater or less than 0 for the x axis, if you aren't perfectly straight.

So the only problem with your code is that it demands perfection from the driver to work. It would be much better to do something like "axis > 0.5" (pick an appropriate number) so you have a range on the joystick where pushing it forward makes it move. That way your driver doesn't have to be perfect!

curtis0gj 05-02-2015 11:48
Re: Limit Swtich Help
 
Quote:
Originally Posted by Jon Stratis (Post 1438657)
Your getting there! It can be hard to learn this stuff remotely without someone experienced there to help.

Your code is actually really close. Joystick axis values are returned as doubles, but that's a good question! There is often a lot of confusion between float and double, as they appear to be basically the same. In situations like thiszits useful to look at the javadoc For the object your using. A quick search turned up a copy here: http://team2168.org/javadoc/ go there and click on "Joystick" in the class listing on the left. You can then scroll through all of the methods in the joystick class, find the one you're using, get a short description of it, and see its return type. Pretty handy!

With the code you posted, the elevator will go up only if you have the joystick pushed full forward so the return value is 1. Pushing it halfway, so you get 0.5, wouldn't move it. Additionally, if you aren't pushing perfectly straight, you won't get a return value of 1! Take a piece of graph paper, draw a set of axis, and then draw a circle with a radius of 1, centered on the origin. Everything inside that circle is a value that can be returned by the joystick. If you push the joystick forward, you could get 0 for the x axis and 1 for the y axis... Or you could get something just a little less than 1 for the y axis and a little greater or less than 0 for the x axis, if you aren't perfectly straight.

So the only problem with your code is that it demands perfection from the driver to work. It would be much better to do something like "axis > 0.5" (pick an appropriate number) so you have a range on the joystick where pushing it forward makes it move. That way your driver doesn't have to be perfect!

Will this work?
Code:
double axis = Xbox.getRawAxis(*));

if(axis  > 0.5) {
    victor1.set(1);
    victor2.set(1);

}

Jon Stratis 05-02-2015 11:54
Re: Limit Swtich Help
 
That looks good to me. Give a try, see if it does what your expecting!

curtis0gj 05-02-2015 13:06
Re: Limit Swtich Help
 
Quote:
Originally Posted by Jon Stratis (Post 1438732)
That looks good to me. Give a try, see if it does what your expecting!
Okay thanks for the help so far I will test it tonight.

curtis0gj 05-02-2015 16:34
Re: Limit Swtich Help
 
I am having a problem where my relay is stuck in forward (showing a green light) or off (showing no light) when I press a button. Here's the code.
Code:
if(xbox.getRawButton(4)) {
                    spike1.set(Relay.Value.kForward);
                    spike2.set(Relay.Value.kForward);
            } else if(xbox.getRawButton(1)) {
                    spike1.set(Relay.Value.kReverse);
                    spike2.set(Relay.Value.kReverse);   
            } else {
                    spike1.set(Relay.Value.kOff);
                    spike2.set(Relay.Value.kOff);                   
            }
            }
    }

Jon Stratis 05-02-2015 17:14
Re: Limit Swtich Help
 
When I read that, it looks like it says "while button 4 is pushed, go forward. While button 1 is pushed, go in reverse. If neither button is pushed, stop" is that not what's happening? Your description of the behavior isn't really complete to tell us what you want to have happen.

Take a look at the user manual for the spike, found here: http://content.vexrobotics.com/docs/...uide-sep05.pdf

It describes the operation of the LED. It's been a while since my team has used one, but I believe it says kForward is green, kReverse is red, kOff is Orange, kOn is blank.

Double check the wiring and make sure it isn't shorting something when you push button 1, I've seen a short cause the LED to turn off before.

curtis0gj 05-02-2015 17:36
Re: Limit Swtich Help
 
Quote:
Originally Posted by Jon Stratis (Post 1438916)
When I read that, it looks like it says "while button 4 is pushed, go forward. While button 1 is pushed, go in reverse. If neither button is pushed, stop" is that not what's happening? Your description of the behavior isn't really complete to tell us what you want to have happen.

Take a look at the user manual for the spike, found here: http://content.vexrobotics.com/docs/...uide-sep05.pdf

It describes the operation of the LED. It's been a while since my team has used one, but I believe it says kForward is green, kReverse is red, kOff is Orange, kOn is blank.

Double check the wiring and make sure it isn't shorting something when you push button 1, I've seen a short cause the LED to turn off before.
The issue is when I press button 1 one relay goes in reverse and the other goes to kOn (LED BLANK) and when I press button 4 it goes in kForward(GREEN). Also the spike is stuck in kForward because it's always green unlike the other which is yellow.

Jon Stratis 05-02-2015 17:48
Re: Limit Swtich Help
 
Double check the orientation of the PWM wire, both in the spikes and in the relay ports on the RoboRio. I have a suspicion that one is plugged in backwards or in the wrong location all together.

curtis0gj 05-02-2015 18:02
Re: Limit Swtich Help
 
Quote:
Originally Posted by Jon Stratis (Post 1438940)
Double check the orientation of the PWM wire, both in the spikes and in the relay ports on the RoboRio. I have a suspicion that one is plugged in backwards or in the wrong location all together.
No I just checked everything looks good the black cable is closest to the edge on the roboRIO and it is facing the correct way on the spike.


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