Can't figuring out what's wrong. Please help.

[Alan Anderson]

Seeing your code would help us help you figure out what's going on.


I'll guess blindly that you're using two buttons, one to raise the arm and one to lower it. You've got a pair of if/then statements (or case blocks in LabVIEW), one for each button, to decide whether to run the motor or stop it. The problem is that if you press the first button to turn the motor on, the second button's else clause (or false case) turns the motor off again immediately.

Does that hit the mark, or am I totally wrong?

[bf2416]

We had that same problem, and based on your description, it sounds like you are using a case structure. Rather than using a case structure, I would use this as an example. I originally used a case structure and had a similar problem. I hope this helps, but if it doesn't or you aren't using NI Labview, sorry.

You can also use the throttle on one of the joysticks to control the motor, but it can be a little touchy, so I would recommend using the above link.

[Taylor]

Does the arm start (relatively) vertical, lower to horizontal, then lift back to vertical? Perhaps the motor isn't strong enough to lift the arm back up.

[slijin]

Originally Posted by Taylor

Does the arm start (relatively) vertical, lower to horizontal, then lift back to vertical? Perhaps the motor isn't strong enough to lift the arm back up.

To elaborate,

Have you counterbalanced your arm?

Don't forget that when pushing something down, gravity works with the motor, but against you when pulling it back up. The same applies to any mechanism that works with gravity one way, and fights it the other way. Sort of like how going down stairs is easier than going up

If you haven't counterbalanced your arm, then that would produce exactly the type of behavior you describe.

[nitneylion452]

If you are using Java, or a language with similar syntax, you'll want a format like this:

if(condition1)
{
    //perform action 1
}

else if(condition2)
{
    //perform action 2
}

and so on.

What this will do is stop checking if a button was pressed after one of the conditions is true. I.e., when condition 1 is true, the program will not check for condition 2 and not execute its else statement (if you have one). If what Alan said is the issue, this should be a relatively simple fix.


Now for everyone to tell me that I'm completely wrong and that this won't work.

[Jon Stratis]

You say "van door motors" - which motors are you talking about specifically? Most teams would be using either the AndyMark Gear Motor (PN am-091) or dual Window Motors (PN 262100-3040 and 262100-3030). To use a van door motor, you would either have access to previous year's KoP's (several years ago they included a Van Door motor, if I remember correctly), or parts from the ARA donation.

If you're talking about the window motors in the KoP, I recall issues being posted in past years with them and specific speed controllers - when pushing against a load, the frequency of the speed controller would cause issues with running it in that direction.

Try switching the controller out for a Spike relay (if appropriate), or removing the locking pin from the window motor (an allowed modification).

[EricH]

Originally Posted by Jon Stratis

To use a van door motor, you would either have access to previous year's KoP's (several years ago they included a Van Door motor, if I remember correctly), or parts from the ARA donation.

FIRST Choice still had the '08 KOP Van Door motors in Week 6, and they are legal to use if you got them from there. I was thinking those would be perfect for dropping the bridge if you could get your hands on them.