How to get encoder direction and speed / rpm ? ( with DT INT ?)

[luminas]

Is there any simple way (minimum code) to get encoder direction and speed / rpm , not position ?

Encoder is incremental type , output are A,B,Z

I am thinking about using DT INT , but not sure where to start .

Could any one point me which direction to go ? Thank you

[HenrikOlsson]

Hi,
Since you're not interested in position one simple way would be to count pulses from one channel for a certain amount of time. The direction could then be determined by polling channel B at the rising edge of channel A - or the other way around. What kind of speeds we're talking about. A couple of 100Hz or several 100kHz or even more? What else is the PIC going to do?

Which PIC are you using? If you haven't decided on one yet then one option is to have a look at the 18F2431 series, it's got a quadrature encoder interface peripheral.

/Henrik.

[luminas]

Thank Henrik !

I am planning to use 16F88 , but I will look at 18F2431 as your suggestion

As for the speed , it just 0 - 10 rpm max , with 100 count encoder.

The pic will then output led indicator direction and speed low - med - high according to rpm , that simple

[HenrikOlsson]

Oh, in that case there's no need for the 18F2431, it would be overkill.
Set one of the PICs timers up as a counter and feed the pulses from one channel to it, then read its value at precise intervals and you have the velocity. Or use the Count command to Count pulses for a certian amount of time. Or, instead of counting pulses, use the capture module to measure the length of ONE pulse. Or use PulsIn to do the same thing, or.....

/Henrik.

[luminas]

Hahaha, yes indeed 18F2431 would be overkill

Okay, the issue with rpm is clearer now, but what about direction ?

[HenrikOlsson]

Like I said earlier, read the state of channel B at the rising edge of channel A and you have the direction.

[richard]

rotary encoders woes are a common issue have a look at this thread


http://www.picbasic.co.uk/forum/showthread.php?t=13177

secondly if your encoder is mechanical type contact bounce is an issue that must be dealt with

[Ioannis]

Also at this PIC:

http://www.microchip.com/wwwproducts...cName=en010291

It has Qudrature Encoder Interface and hardware filters too!

Ioannis