Chief Delphi - Sensing RPM with the kit encoder.

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- - Sensing RPM with the kit encoder. (http://www.chiefdelphi.com/forums/showthread.php?t=100198)

Ty Tremblay

14-01-2012 16:40

Sensing RPM with the kit encoder.

Can the CRio keep up with the counts from the kit encoder if it's on a shaft rotating at 2500-3000 rpm? I'd like to run a velocity PID on our shooter. IIRC, the kit encoder doesn't have an indicator pulse, meaning you'd have to count all of the pulses. However, I don't know how many PPR the kit encoder has.

davidthefat

14-01-2012 17:10

Re: Sensing RPM with the kit encoder.

Code:

private double[] getRPM()

    {

        double rpm[] = new double[2];                                               //Declares an array of integers which the function will return.

        currentTime = time.get();                                                   //Sets currentTime to the time calculatged from FPGA

        rpm[0] = leftEncoder.getRaw() * 16666666.666666 / currentTime;              //dAngle*(60000000us/360deg)/dTime = RPM

        rpm[1] = rightEncoder.getRaw() * 16666666.666666 / currentTime;             //dAngle*(60000000us/360deg)/dTime = RPM

        leftEncoder.reset();                                                        //Resets the left wheel encoder.

        rightEncoder.reset();                                                       //Resets the right wheel encoder.

        time.reset();                                                               //This resets the timer.

        return rpm;

    }

Ty Tremblay

14-01-2012 17:25

Re: Sensing RPM with the kit encoder.

Thanks for the code. :p Im just asking if the FPGA can keep up with the speed that the counts will come in from a 3000 rpm shaft.

Ether

14-01-2012 17:58

Re: Sensing RPM with the kit encoder.

Quote:

Originally Posted by Ty Tremblay (Post 1105497)

Thanks for the code. :p Im just asking if the FPGA can keep up with the speed that the counts will come in from a 3000 rpm shaft.

https://decibel.ni.com/content/message/12523#12523

Mark McLeod

14-01-2012 18:10

Re: Sensing RPM with the kit encoder.

The US Digital KOP encoders are 360 CPR.
They are rated at 10,000 max RPM

At 1X the cRIO will keep up.

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