Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: kdoney on July 17, 2009, 07:38:07 PM

Title: Pulse on scope but not being seen by machturn
Post by: kdoney on July 17, 2009, 07:38:07 PM

I went into ports and pins and tried every combination of high, low, port on pin 11, my encoder input pin and machturn will not see it. It shows up on the scope at all speeds. Calculated correctly at 1 rpm. I used the automatic setup of input but still no luck.
Any ideas?

Title: Re: Pulse on scope but not being seen by machturn
Post by: Dan13 on July 18, 2009, 12:58:15 AM

Are you using a breakout board?

Daniel

Title: Re: Pulse on scope but not being seen by machturn
Post by: Hood on July 18, 2009, 03:03:16 AM

If this is the Index pulse from an encoder and you are using the Parallel port then it is unlikely to work as the pulse will be too short for the Parallel Port to see properly.
Hood

Title: Re: Pulse on scope but not being seen by machturn
Post by: kdoney on July 18, 2009, 10:51:59 AM

Yes, I am using the pmdx 132.

Title: Re: Pulse on scope but not being seen by machturn
Post by: Dan13 on July 18, 2009, 12:54:03 PM

Hood raised a good point. If you're using an encoder then the pulse is too sort for the parallel port to be seen.

If it's not the case then I would check the PMDX input.

Daniel

Title: Re: Pulse on scope but not being seen by machturn
Post by: kdoney on July 18, 2009, 01:21:18 PM

I guess I can build a longer signal triggered by the real one. I don't see how that is going to help synchronize with the spindle speed though. If I increase the signal length that will limit my speed to whatever length I increase it to / what ever rpm the spindle is moving.

 ???

Title: Re: Pulse on scope but not being seen by machturn
Post by: Dan13 on July 18, 2009, 01:38:30 PM

You are not quite correct. Mach3 needs the index pulse to be at least 200 microseconds to reliably read it. That means that your speed can be as high as about 150,000RPM as far as Mach3 is concerned (considering that it takes 200 microseconds for the pulse high state and the same amount of time for the pulse low state).

The simplest way to go, and one that I used before I had a servo on my spindle and SS to read the encoder index, is to build a simple circuit based on the 555 IC. You can calculate the resistors you need to get a pulse width just above 200 microseconds. It had worked perfectly for me.

Daniel

Title: Re: Pulse on scope but not being seen by machturn
Post by: kdoney on July 18, 2009, 01:43:25 PM

Thanks all! :)