[kstrauss]

Sorry to belabor the point but I'm confused. I assumed that one would use the second port on the 5i25 in order to use the quadrature capability on the Mesa card. Mesa has a 7i76 which provides isolation but I'm unclear what cable is required to connect it to the internal port on the Mesa card.

[jcposada]

Sorry to belabor the point but I'm confused. I assumed that one would use the second port on the 5i25 in order to use the quadrature capability on the Mesa card. Mesa has a 7i76 which provides isolation but I'm unclear what cable is required to connect it to the internal port on the Mesa card.

See post #23. That cable will give you access to the second parallel port on the Mesa card. Then connect that to a C10 bob with a standard parallel cable.

[PCW_MESA]

Sorry to belabor the point but I'm confused. I assumed that one would use the second port on the 5i25 in order to use the quadrature capability on the Mesa card. Mesa has a 7i76 which provides isolation but I'm unclear what cable is required to connect it to the internal port on the Mesa card.

You typically use 2 cables for this, the first is a short flat cable from the internal 5I25 connector
to a PC bracket mounted DB25F (to get the signals out of the PC) and then a standard DB25
male-male IEEE-1284 printer cable to go to the 7I76

DB25F-IDC26 CABLE
http://store.mesanet.com/index.php?r...=239&search=db

for example (these are generally available from Monoprice etc)

[SoCalPlaneDoc]

Sorry to belabor the point but I'm confused. I assumed that one would use the second port on the 5i25 in order to use the quadrature capability on the Mesa card. Mesa has a 7i76 which provides isolation but I'm unclear what cable is required to connect it to the internal port on the Mesa card.

Looks to me cable like this one should do the trick:
※※※NEW ※※※ DB25 LPT1 Parallel 25-Pin Printer Port Full Height Bracket 12" Cable | eBay

You'd still need another 7i76 and cable though. Does anyone see and operational advantage to this over an old-fashioned printer port and BOB?

[PCW_MESA]

You can use a standard parallel port BOB with the second 5I25 port (a 7I76 is extreme overkill for just adding an encoder)

Advantages of using second 5i25 port:

1. Real encoder counter, so no base thread needed (widens host PC choices since you do not need very good real time latency for just a 1 KHz servo thread )
also supports high resolution encoders

2. Only one card needed if theres no MB parallel port (say on mini-ITX MBs which have only one available PCI/PCIE slot)

Advantages of using parallel port:

1. Somewhat simpler setup ( no firmware changes)

2. if a plug-in PP is used a damaged port is a $10 replacement as opposed to a $90 replacement for a 5I25

[SoCalPlaneDoc]

You can use a standard parallel port BOB with the second 5I25 port (a 7I76 is extreme overkill for just adding an encoder)

Advantages of using second 5i25 port:

1. Real encoder counter, so no base thread needed (widens host PC choices since you do not need very good real time latency for just a 1 KHz servo thread )
also supports high resolution encoders

2. Only one card needed if theres no MB parallel port (say on mini-ITX MBs which have only one available PCI/PCIE slot)

Advantages of using parallel port:

1. Somewhat simpler setup ( no firmware changes)

2. if a plug-in PP is used a damaged port is a $10 replacement as opposed to a $90 replacement for a 5I25

Excellent intel PCW.. thanks.. as to the firmware, Did I see somewhere there was a version already for running 2 ports?

[kstrauss]

I assume that it depends on the shaft encoder. With a 1000 line encoder I think that means 2000 transitions/rev/channel. At 2000 rpm this is 67000 transitions/sec times two (A,B channels) or 133K/sec or a transition every 7.5 microseconds. That seems excessive for the PC to have to process each of them via the parallel port. (Please check my arithmetic!) On the other hand perhaps a 1000 line encoder is huge overkill just for tapping. What sort of encoder do commercial machines such as a Haas use?

[PCW_MESA]

People have done have done tapping successfully with LinuxCNC using fairly crude encoders (say ~ 50 lines or 200 counts)
Finer threads will be less picky about the spindle feedback because the Z axis errors during reversal are correspondingly smaller

[SoCalPlaneDoc]

I assume that it depends on the shaft encoder. With a 1000 line encoder I think that means 2000 transitions/rev/channel. At 2000 rpm this is 67000 transitions/sec times two (A,B channels) or 133K/sec or a transition every 7.5 microseconds. That seems excessive for the PC to have to process each of them via the parallel port. (Please check my arithmetic!) On the other hand perhaps a 1000 line encoder is huge overkill just for tapping. What sort of encoder do commercial machines such as a Haas use?

As it happens, the encoder I was going to use is a 1000 - using it just because I already had it and it's meant for harsher environments:
BEI L25G-F3-1000 http://www.beisensors.com/pdfs/l25-o...al-encoder.pdf

I doubt I would ever run it over 500 rpm to tap, putting same-size pulleys on it and it's rated to run at 10K max so it should be happy when doing other machining..
I don't have any idea what HAAS uses.. every time I get close to one of the machines at work the CNC guys start to hyperventilate Don't they know Mechanical Engineers can fix problems they didn't even know they had, using methods no one understands??

[kstrauss]

I have a 770 rather than a 1100 so coupling an encoder to the spindle without significant RPM reduction limits the choices for encoders. Using something like SoCalPlaneDoc's design would be easy to mount to the pulley.

If the only use is for rigid tapping do we need an index pulse?