Chief Delphi - 8 volts over talons

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Re: 8 volts over talons

I have never come across a problem that's baffled me as much as this has. Is it possible to calibrate the talons while applied on a button, or does it have to read Y-axis for it to work.

Re: 8 volts over talons

To calibrate the Talons, you should bring them through the full -1 to 0 to 1 range.

Code:

1. Press and hold the button labeled “CAL” with a paper clip. The

LED should begin to blink red/green.

2. Continue to keep the button pressed while moving the joystick

full forward and full reverse. You may do this as many times as

you like.

3. Center the joystick and then release the CAL button.

4. If calibration was successful, the LED will blink green several

times. If the LED blinks red several times, the calibration was

not valid. If this happens, the Talon will use the last valid

calibration values.

Did the new project with just the button code work?

Re: 8 volts over talons

To answer the electrical questions. The shooter is composed of two CIMs, brand new. Talons, out of the box, and PWMs from AndyMark. The solder-less terminals that connect the wiring are all solid. The raceway for ALL these wires are not ran in a configuration that runs against the chassis or may have been cut, all clean, short, out in the open runs. Instead of having the load on the motors, the multimeter replaced the terminals on the talons so when the actions are live, we have the 12V and the 8V read outs on the display and the Talon LED indicator light.
With this program are two limit switches that prevent the arm to destroy it's self when it fires, and when it returns back to loading position.

They work fine, we get zero volts when they are depressed.

Re: 8 volts over talons

Quote:

Originally Posted by TFleig78 (Post 1366566)

Did the new project with just the button code work?

When last tried, no it didn't work. Gave an 8 volt reading. the difference in speed was noticeable

Re: 8 volts over talons

I'm not sure that reading the output of the Talon with a voltmeter is the correct approach to understanding what is happening. You see the output of a speed controller is a pulsed output that switches between 0 and 12 VDC.
It's the duty cycle (ratio of on to off time) that determines the speed of the motor. What you are probably seeing is the average voltage that the meter is reading over time. An oscilloscope is a better tool to use for this application.
Now having set that straight, I am also puzzled why you are reading a different average voltage output based on whether the joystick axis or the programmed button is providing the controlling input to the Talon's PWM input. If you have access to an oscilloscope can you see a difference in the pulse width of the PWM output to the Talon?

Re: 8 volts over talons

Quote:

Originally Posted by BitTwiddler (Post 1366840)

If you have a speed controller hooked up to a motor (which the OP said he does), you'll only read the average voltage, even with a scope - trust me, I've seen it. I was doing a demo for the team to show them how a speed controller output works, and was puzzled for about 5 mins when i just saw the average voltage... had to unplug the motor to actually be able to see the waveform.

Re: 8 volts over talons

One problem I see with your code, although it shouldn't cause the problem you are seeing, is that the motor will not turn off if you release the button. You should probably change it to something like:

Code:

if(js.getRawButton(11)){

    shooter.set(1.0)

    }else{

    shooter.set(0.0)

}

Re: 8 volts over talons

Quote:

Originally Posted by JavaNoNothing14 (Post 1366656)

When last tried, no it didn't work. Gave an 8 volt reading. the difference in speed was noticeable

But having shooter.set(1.0) with the getAxis() instead of the getRawButton() gives you 12V?

What happens if you bind it to another button?

Re: 8 volts over talons

Quote:

Originally Posted by Zaque (Post 1366863)

Code:

if(js.getRawButton(11)){

    shooter.set(1.0)

    }else{

    shooter.set(0.0)

}

right, i only had it set to the shooter.set(1.0) so that no other code could be the problem, even if its just to stop the shooter.

Re: 8 volts over talons

Quote:

Originally Posted by Patrick Chiang (Post 1366870)

But having shooter.set(1.0) with the getAxis() instead of the getRawButton() gives you 12V?

What happens if you bind it to another button?

I understand that a voltmeter is not the best possible route to actually read what the talon's output is but when i have it set to getY(); the wheels move at nearly twice as fast. I have not tried testing it to another button, and won't get a chance to unfortunately until the regional.

I thank everyone for trying to get to the bottom of this problem..

Re: 8 volts over talons

Quote:

Originally Posted by JavaNoNothing14 (Post 1366915)

Err... is it possible that set() is broken and you were setting it to a higher than 1.0 value (maybe because getY() returns more than 1.0)? Try setting it manually to something ridiculously high like 100.0.

Or maybe a limiter was implemented that lowered it if it went too high, and getY() would return values like 0.99583953 which would go through, but having it be 1.0 will get it artificially lowered in the program to say 0.7?

Just throwing ideas out there.

Re: 8 volts over talons

Quote:

Originally Posted by Jon Stratis (Post 1366852)

Hmm. Sounds like I need to take a look for myself. I've never actually looked at a motor controller output. Make sense though since the motor inductance is probably distorting the pulse edges.

Re: 8 volts over talons

Quote:

Originally Posted by JavaNoNothing14 (Post 1366915)

Maybe the problem is more subtle than passing a numeric value to the robot from the DS. Is it possible that data packets are being dropped in the comms? Don't know why that would affect the discrete values versus the variable joystick output though. Do you have a motor timeout set in your initialization code?

Grasping at straws maybe but I really think the problem lies elsewhere.

Re: 8 volts over talons

Quote:

Originally Posted by BitTwiddler (Post 1366991)

Ohhhhh, I just had a brainwave as I was typing this. You code looks fine, if you're always doing Set(1.0) and just switching from GetRawButton to GetAxis in your if condition, then it can't be an electrical issue. Clearly the problem must lie in GetRawButton. Can't be an issue in your code because your GetAxis works, and GetRawButton doesn't. Ergo, the problem has to be with the buttons themselves or GetRawButton.

Button state gets pulled directly from the control structure that gets set by the FRCComms library, so it's not like you can accidentally reset the state of the button in code. As far as I know, when you drop comms, the robot uses the last recieved values, so unless it's dropping long enough to fault things (which you'd notice driving), I don't think it's a comms problem. A comms problem that severe should affect things if you're using GetAxis anyways.

No, I'm betting it's a windows driver/joystick setup issue. I'm going to bet that (somehow) your joystick is setup to treat holding down that button like rapidly pressing the button. So you think you're holding it, but it's actually flickering off and on, and that's getting reflected in the data from the driverstation. So if you have code for turning the motor off when the button is released, you're actually constantly turning the motor on full speed, then off. Sort of an unintended PWM on top of the PWM.

Testing this theory:
Set up a variable to count edges on that button and check the value of that variable. Something like:

Code:

//In Robot class variable declarations

bool oldButton = false;

int edgeCount = 0;



//In your Teleop loop



if (oldButton != js.getRawButton(11))

  edgeCount++;

oldButton = js.getRawButton(11);

//printf edgeCount here or write to the DSLCD, or however you want to monitor it.

If things are working properly, edgeCount should only increment once(ish) when you press the button, and once(ish) when you release it. It shouldn't increment while you're holding down the button. If it DOES, then the driverstation is sending bad data or windows is telling the driverstation that the button is flickering off/on.

Solution:
1. Figure out why the DS or windows thinks the button is flickering. I don't know the details of your joystick/laptop setup, so you get to have fun with that. Best solution because it actually fixes the problem.
2. Two separate buttons, one to turn on the shooter, on to turn it off. Worst solution because it complicates things for your drivers.
3. Debounce the OFF side of the button press. It's tricky, but you're basically looking for the button to be off for several loops in a row, to be sure it's actually off and not flickering. This solution should fix things even if the problem is comms dropout.

Code:

//In Robot class variable declarations

bool buttonState = false;

int offCount = 0;



//In Teleop initialization

buttonState = false;

offCount = 0;



//In Teleop Loop



if (buttonState)

{

  if (!js.getRawButton(11))

    offCount++;

  else

    offCount = 0;

  if (offCount > 10)      //10 is the number of loops we need to see

    buttonState = false;  //the button off to decide it's actually off

}

else

{

  //will set buttonState true when first sees button pressed

  buttonState = js.getRawButton(11);

  offCount = 0;

}



if (buttonState)

{

  shooter.set(1.0)

}

else

{

  shooter.set(0.0)

}

That will immediately turn the shooter on, then needs to see the button off for 10 loops before it actually turns the shooter off. Tweak the 10 loops to be as small as possible while still giving you consistent 12V output. I don't think you'd need to make it more than whatever's equivalent to 0.2 sec. I'd guess that 0.1 sec would work fine. You want it to be short, because the motor will keep running for that long after you let go of the button.

Note that if this is affecting this particular button, it could potentially affect ANY button where you're changing state based off whether the button is pressed or released. It won't affect things where you just set things if the button is pressed and do nothing if released.

Re: 8 volts over talons

Also, you really need to post back here with what the problem and solution is because I'm super curious and will PM you endlessly if you don't.