Window Motor Problem?

[cdizzle]

It seems like a coding problem, but I can't figure out what the problem is at all. We tried both a Victor and a Jaguar, so I don't think that is the problem. The code is very standard, I just wired two buttons to a case block. And for one of them, I ran the motor forward when it was true, and backward when it was false. The motor itself is upside down, so it doesn't work properly when the motor is turning forward, but it works well in reverse.

[Kevin Sevcik]

Originally Posted by cdizzle

It seems like a coding problem, but I can't figure out what the problem is at all. We tried both a Victor and a Jaguar, so I don't think that is the problem. The code is very standard, I just wired two buttons to a case block. And for one of them, I ran the motor forward when it was true, and backward when it was false. The motor itself is upside down, so it doesn't work properly when the motor is turning forward, but it works well in reverse.

I'm having difficulty parsing what you're doing. You've wired two buttons to one case block? Are you having one button that turns the motor on/off and the second one that picks the direction? I think it'd be a lot clearer if you posted the VI or a screenshot of it.

[cdizzle]

Originally Posted by Kevin Sevcik

I'm having difficulty parsing what you're doing. You've wired two buttons to one case block? Are you having one button that turns the motor on/off and the second one that picks the direction? I think it'd be a lot clearer if you posted the VI or a screenshot of it.

I'm really sorry, but my code's all at the lab, so this is the best that can do for now, but I'll try to explain it as well as I can.

I have 2 case blocks. One case block is wired to button 3 on our joystick. When that case is true, it sets the motor speed to -0.9. That one works smoothly. I also have another case block which is wired to button 4 on our joystick. When that case is true, it sets the motor speed to 0.9. When I press that button, the motor moves in the right direction, but it stops and jerks forward and then stops again. Note that I haven't put anything in the false part of the case blocks.

Thanks so much for your help and once again I'm really sorry that I can't post a screen shot right now.

[Kevin Sevcik]

Originally Posted by cdizzle

I'm really sorry, but my code's all at the lab, so this is the best that can do for now, but I'll try to explain it as well as I can.

I have 2 case blocks. One case block is wired to button 3 on our joystick. When that case is true, it sets the motor speed to -0.9. That one works smoothly. I also have another case block which is wired to button 4 on our joystick. When that case is true, it sets the motor speed to 0.9. When I press that button, the motor moves in the right direction, but it stops and jerks forward and then stops again. Note that I haven't put anything in the false part of the case blocks.

Thanks so much for your help and once again I'm really sorry that I can't post a screen shot right now.

That's certainly a recipe for weirdness if you're pressing both buttons at once. Also, how on earth does your motor stop after you let go of a button? If you let go of the counter clockwise button, does the motor stop or keep going? If your motor stops then you're clearly setting the motor speed to 0 somewhere else, since it's not in your false cases. If you're setting speed to 0 elsewhere, then your button 3 code is beating out the zero speed code and keeping things moving. Your button 4 code occasionally loses to the zero speed code and thus sometimes the motor stops, and sometimes it moves. Assuming you're setting speed to 0 somewhere.

What I like to do for programming two buttons to turn a motor is to pick a dominant case. That means that you pick one of the buttons that "wins" if both buttons are pressed. Then you can pretty easily use two Select blocks to set the motor speed. See my attached code snippet, in which button 3 "wins" and gets final say in the motor speed.

[nicholsjj]

You could try switching imput buttons on your joystick to see if that helps also. I know our gamepads had a glitchy button on it. You might want to put the -1 value and then invert that into you motor output to see if it works also.

[cdizzle]

Originally Posted by Kevin Sevcik

That's certainly a recipe for weirdness if you're pressing both buttons at once. Also, how on earth does your motor stop after you let go of a button? If you let go of the counter clockwise button, does the motor stop or keep going? If your motor stops then you're clearly setting the motor speed to 0 somewhere else, since it's not in your false cases. If you're setting speed to 0 elsewhere, then your button 3 code is beating out the zero speed code and keeping things moving. Your button 4 code occasionally loses to the zero speed code and thus sometimes the motor stops, and sometimes it moves. Assuming you're setting speed to 0 somewhere.

Wait, so if I set my motor speed to 0 when false in the case block for button 3, will it affect the motor when the button 4 case block is true?

Originally Posted by nicholsjj

You could try switching imput buttons on your joystick to see if that helps also. I know our gamepads had a glitchy button on it. You might want to put the -1 value and then invert that into you motor output to see if it works also.

Yeah, we tried both of those things, and neither worked.

[nicholsjj]

[quote=cdizzle;1230855]Wait, so if I set my motor speed to 0 when false in the case block for button 3, will it affect the motor when the button 4 case block is true?


No it should just affect the output from case three. My next question is are you sending both button outputs into the same motor set output vi. This might be where Kevin's statement about overriding can occur if you use two different vi's.

[Kevin Sevcik]

Originally Posted by cdizzle

Wait, so if I set my motor speed to 0 when false in the case block for button 3, will it affect the motor when the button 4 case block is true?

Originally Posted by nicholsjj

No it should just affect the output from case three. My next question is are you sending both button outputs into the same motor set output vi. This might be where Kevin's statement about overriding can occur if you use two different vi's.

If you have two completely separate case blocks for button 3 and 4, then yes, the false case in the button 3 block will affect button 4 even if button 4 is true. See my attached snippet. The top two show the cases in the case blocks. The bottom shows what will run when button 3 is false and button 4 is true. Both of those case blocks will run, which means you're trying to set the motor speed to 0 and set the motor speed to 0.9 at the same time. The results of trying to set the motor to two different speeds simultaneously are not particularly predictable.

Cecil's suggestion of putting the motor set block outside of the cases is also a good one. Then you know that you only have one motor set and it's only going to run once. Then you just have to figure out how to send it the appropriate value. It makes it pretty obvious if your value selection method isn't valid because you'll end up trying to wire two thing to the same input, which labview will complain about.

[cdizzle]

I got it working! Thanks for your help guys! I think something was overriding the reverse command, but I couldn't figure out what it was, so I just wired it to one SetMotorSpeed like you guys said to.

[Kevin Sevcik]

Originally Posted by cdizzle

I got it working! Thanks for your help guys! I think something was overriding the reverse command, but I couldn't figure out what it was, so I just wired it to one SetMotorSpeed like you guys said to.

Just as long as you remember this and apply that design pattern to the rest of your systems so you don't have the same problem in the future.

[Cecil]

Originally Posted by Kevin Sevcik

What I like to do for programming two buttons to turn a motor is to pick a dominant case. That means that you pick one of the buttons that "wins" if both buttons are pressed. Then you can pretty easily use two Select blocks to set the motor speed. See my attached code snippet, in which button 3 "wins" and gets final say in the motor speed.

What I've always done is just put the numbers in the case statements, with the Set VI outside the case. The true cases have the values to set the motor to, and the false cases both have 0 in it. Just to the right of the case, I put an addition operator in. That way, if one button is pressed, it adds 0, not affecting the output. 0+0 = 0, x+0 = x, and x+y=0. (Of course, this only works when both positive and negative values are the same...)

Edit: I also use the Select statement for the values, not just cases. Keep forgetting I usually put global sets in there too.