Chief Delphi - Encoder Help

Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Java (http://www.chiefdelphi.com/forums/forumdisplay.php?f=184)

- - Encoder Help (http://www.chiefdelphi.com/forums/showthread.php?t=154237)

Hello everyone! I was wondering how I would use encoders to figure out how far our robot would drive in autonomous? A big thanks in advance for those who are willing to help. :D

Re: Encoder Help

Quote:

Originally Posted by Team5709 (Post 1636222)

Hello everyone! I was wondering how I would use encoders to figure out how far our robot would drive in autonomous? A big thanks in advance for those who are willing to help. :D

You need to provide more information and be more specific. You should ask a question like this: "With a CANTalon SRX, how can I use a Hall Effect Two Channel Encoder (am-2816a) to read a velocity?"

You need to wire an encoder to your motor controller, and then read that encoder, usually from that motor controller.

Re: Encoder Help

With a general question, you get a general answer.

The encoder delivers a fixed and known number of pulses per revolution. If you have a 200 pulse-per-revolution encoder, for example, each time the shaft to which it is mounted turns one revolution, your RoboRIO will see 200 pulses.

If you then calculate how far your robot goes in one revolution - Pi is your friend here - you can then measure distance by counting pulses. This is known as Odometry.

Many encoders have a second "orthagonal" output, which can be used to determine the direction of rotation.

Also be aware that some encoders do not output pulses, but instead a variable voltage or some other 'thing' - and we're not discussing those kinds of encoders here.

Good luck!

Re: Encoder Help

Quote:

Originally Posted by Team5709 (Post 1636222)

Hello everyone! I was wondering how I would use encoders to figure out how far our robot would drive in autonomous? A big thanks in advance for those who are willing to help. :D

Answer these questions and you may get more detailed help:

what is the part number of the encoders

how are the encoders wired [roboRio or SRX]

where are the encoders mounted

what is the gear ratio between encoder and wheel

what kind of drivetrain are you using

what is wheel diameter

what model motor controllers are you using

are you using PWM or CAN bus

Re: Encoder Help

If you haven't made any of the decisions yet about what encoders to use and need help with THAT, knowing the specifics of your gearbox (make and model type stuff) as well as the other things Ether mentioned that you DO know will help in getting those answers.

Re: Encoder Help

Quote:

Originally Posted by Ether (Post 1636274)

Exactly! This information is important to solving the problem that you have. Jumping headfirst into a problem like "How can I make the robot drive 5 feet with encoders" can be daunting, so you should break it down into simpler pieces first :)

Re: Encoder Help

Encoder: Encoder Kit AMT103-V (fc17-033)

they will be wired into the RoboRio. They are mounted on the out put shaft of the drive gear boxes. one on the left and one on the right. There is no gear ratio because its on the out put shaft and not on the motor it self. We are gonna be using arcade drive. The wheels are the 6 inch wheels (http://www.andymark.com/HiGrip-Wheel...?1=1&CartID=0). The motor controllers we are using are the 2015 Talon KOP controllers and those are using PWM.

Re: Encoder Help

Quote:

Originally Posted by Team5709 (Post 1638047)

Check out the screensteps reference: http://wpilib.screenstepslive.com/s/...or-other-shaft

And check out how to configure your encoder's pulses per revolution on the datasheet, page 4 http://www.cui.com/product/resource/amt10.pdf
Keep "maximum rpm" in mind when choosing a value. Choose the highest number of ticks that fits your intended rpm for the best accuracy.

Then you can get distance like this

Code:

Encoder enc = // create encoder as per screensteps

int ticksPerRev = // what you set them to

double diameter = 6.0; // inches

double distancePerRev = diameter * Math.PI;

enc.setDistancePerPulse(distancePerRev / ticksPerRev);



// later

double currentDistance = enc.getDistance(); // in inches

Edit: I'm unfamiliar with the 2015 KOP, but if those are Talon SRX controllers, you're a lot better off using CAN than PWM, because you can connect the encoders directly to Talons for high rate PID control.