Campbell Breakout Board

[wildcat]

What is the general concensus on using a breakout board with an IH CNC? Is there any reason (other than saving some cash) not too? Seems like there are many good reason to do so.

Thanks

[wildcat]

Anyone here using this or any breakout board? I am leaning towards one with my kit arrive tomorrow but would like to know if there are any gotchas to be aware of when using the board from Bob.

Thanks

[MAX711]

I used the CNC4PC board with mixed results. The first 1 had to go back because it didn't provide enough current to drive the Geckos all the time. The second one would only work on certain outputs, but it's working fine now. Don't know anything about the Bob Campbell board though, sorry. You definitely need a breakout board though, 1 to make the connections easier and 2 to protect your computer.

[wildcat]

Thanks for pointing out the CNC4PC board - I had not seen that one before. Quite a price difference between it and the Campbell board.

[Loadedagain]

i use two campbell boards and one of his relay boards with my ih cnc. can't recommend him enough. excellent product and... you do get what you pay for!

[wildcat]

That's what I needed to hear - got one ordered up.

Thanks

[Richards]

I have two PMDX-122 boards that I've been using for about a year without problems of any kind. Another user mentioned that his VFD created enough electrical noise when his PC was either off or not running Mach 3 to cause the outputs on his PMDX-122 to change state randomly. A suggested work-around is to add pull-up resistors to the input lines on the board (which would cost about $1.00 and take about five minutes if one end of each resistors were simply inserted into the wire terminals of a signal line and the other ends of all the resistors tied together and connected to a 5VDC line from the PMDX board).

[BobWarfield]

Richards brings up an interesting thought. Be really careful around a CNC machine. Don't have the drivers powered up if there is no PC in charge. A lot of these breakout boards have a safety charge pump circuit for that purpose.

Alternatively, it isn't that hard to wire a circuit that will not apply power to your motors until your PC or other front end controller (mine is a GRex) has had time to boot up. Shut down said PC or front end, and the power goes off for the motors.

I used a delay-on-make relay for my circuit. This is a handy little relay that waits a specified amount of time after it "sees" lline voltage before letting it through. You can set the interval from a few seconds up to minutes. That relay gets the line voltage going into my GRex (or your PC), waits long enough for it to boot, and then sends it on to power up the motor DC supply.

Be sure if you are going to cut power you do it in the right way so as not to blow your Geckos--you want to just cut the power to the DC supply. The filter capacitor will let it down gently. Don't just stick a relay (or a fuse for that matter) between your Geckos and the motors.

I've also wired a hard E-Stop (actually a couple) between this delay on make relay and the line voltage. If I hit one, it also pulls the power to the motors. Lastly, my spindle gets its juice here too. I'm gonna be hitting those E-Stops any time I have to reach my hands into that machine to change cutters or whatever--I want to know without any doubts there is no juice to those motors.

Just a thought!

Best,

BW

[wildcat]

I started wiring an IH CNC kit to a Campbell board and wondered if someone would explain how to power the limit switches. Aaron's wiring diagram calls for 5V but I don't see a dedicated 5V supply on the board for this. Perhaps I can use the 5V that feeds the geckos? Alternatively perhaps I could put a resister to cut the voltage down... What do you think?

Thanks

[Richards]

I'm extremely conservative when it comes to hooking up devices. In my prior life, I designed, programmed and installed process control computers in the photo industry to run the Kodak-S series printers found in most professional photo labs (before the digital photo revolution made my services as valuable as a buggy whip manufacturer). I always use opto-isolators whenever interfacing anything into a control board. That means that the limit switches would have their own power supply and that the only connection between them and the controller board (breakout board) would be light pulses. The inexpensive Texas instruments TIL-111 series of opto-isolators can usually be purchased for a few cents each. My favorite is the Opto-22 G4 modules that run about $15 each for input modules, although they require a 'rack' for another $70 or so.

Connecting signal lines on a machine that has stepper/servo motors, VFDs and assorted other mechanical/electrical devices directly to a controller board is just asking for problems, either now, or sometime down the road. An extra $10 to $250 dollars up front to do things right will keep you safe and sane.

Some breakout boards are already opto-isolated. (I'm not familiar with the Campbell board - which might work perfectly right out of the box.) If that's the case, then you would only have to add a power supply that is independant of the controller's power supply to keep things isolated.

[wildcat]

Anyone know how to interface the Geckos so that a fault causes Mach3 to stop? The behavior currently is that the Gecko faults but Mach thinks the moter is still moving.

[BobWarfield]

I'm assuming by "fault" you mean a servo fault and you are using a Gecko 320 to drive it. The doc for that drive (http://www.geckodrive.com/photos/G320_REV-4_MANUAL.pdf) discusses how to access its ERROR output and still allow the drive to be reset via a switch. If you've got an output, and enough inputs on your breakout card, you can presumably send the result back to Mach and set up Mach to shut things down on a fault, much as it would if you hit a limit switch. This will require a bit of macro work as well as a bit of electronics, so you'd best get some help on the Mach and Gecko support boards if you really want to pursue the option.

Best,

BW