Mach 3 interface to stepper motor driver

[dhookings]

Hi all,

First post in CNCzone. I have aquired an old, but quality looking machine. It originally had an rs232 interface but the original software is missing and I believe it did not use g codes anyway. I am retaining a lot of the electronics, incuding the octal relays, xyz stepper drivers and power supplies. I have purchased Mach3 to drive from my pc lpt port. I am building an interface board from the lpt port to the L297 stepper driver/translators. My interface will include an AVR to detect the charge pump signals and to drive the L207s etc.
To the point, at last.
I would like to use optocouplers to isolate the lpt port from the machine electronics, but am worried about the source capabilities of the lpt port. The led in the optocoupler will take about 15ma and I read that 1284 level 2 ports will source 14ma. I should be able to compromise there, but the original lpt ports were only specified for 1.5ma or thereabouts. If I buy an off the shelf pci board is it likely to be 1284 level 2? Are all modern pcs built to the new standard? If so, how far back can I safely go? Do the commercial breakout boards have optical isolation?

Anyone done this?

Regards


Dave

[dhookings]

6n137 optocouplers do the job.

[m0m022]

can u please inform more details about the interface board between the parallel port and the drive board of the steppers?

[dhookings]

Blimey!

We're going back a bit here.

When I get home I'll dig out my schematics and any other information and post them here.


Dave

[dhookings]

OK,

Here are pictures of my pcb, top side red and bottom, mirrored, blue.
Looking at the top, the lead to the parallel plug is top right and the limit switches etc are bottom right. Two relays top left switch the spindle motor and something I can't remember. The power to the steppers are bottom left. The two multi pinned connectors at the bottom are signals to the three stepper drivers. A bit overkill, but I used the original two driver boards and salvaged the connectors from the original interface board.
There may have been a few modifications, for instance I prefer to operate the spindle manually.

Dave

[pminmo]

Hi all,

First post in CNCzone. I have aquired an old, but quality looking machine. It originally had an rs232 interface but the original software is missing and I believe it did not use g codes anyway. I am retaining a lot of the electronics, incuding the octal relays, xyz stepper drivers and power supplies. I have purchased Mach3 to drive from my pc lpt port. I am building an interface board from the lpt port to the L297 stepper driver/translators. My interface will include an AVR to detect the charge pump signals and to drive the L207s etc.
To the point, at last.
I would like to use optocouplers to isolate the lpt port from the machine electronics, but am worried about the source capabilities of the lpt port. The led in the optocoupler will take about 15ma and I read that 1284 level 2 ports will source 14ma. I should be able to compromise there, but the original lpt ports were only specified for 1.5ma or thereabouts. If I buy an off the shelf pci board is it likely to be 1284 level 2? Are all modern pcs built to the new standard? If so, how far back can I safely go? Do the commercial breakout boards have optical isolation?

Anyone done this?

Regards


Dave

You can sink 20ma on all the output pins. Odd's are that a PC that will run mach3 will source 20ma on pins 2 through 9, but it's not a guarantee. For mach3 you need a fast optocoupler, HPCL263x or HPCL 253x or those series P/N's. If you need a reference design take a look at one of mine: http://pminmo.com/4axisopto/4axisDIYopto.htm

[dhookings]

You can sink 20ma on all the output pins. Odd's are that a PC that will run mach3 will source 20ma on pins 2 through 9, but it's not a guarantee. For mach3 you need a fast optocoupler, HPCL263x or HPCL 253x or those series P/N's. If you need a reference design take a look at one of mine: http://pminmo.com/4axisopto/4axisDIYopto.htm

We are a bit out of step here. I've actually had this machine running for quite some time. However, version 2 may be a consideration. Time permitting I will do some more research on my drivers, with a view to getting faster rapid movement.

Regards

Dave