second hand cnc from 2007,could use help with pwm on odd control board

beau wrote:

your saying that I can lose the two other boards and im not gonna suffer any loses for it?


 

I'm suggesting it's worth a shot.

The PMDX has no step signal timing buffer or complex microcontroller onboard - it's just passing the signals to/from the PC.

The 'controller board' thing doesn't appear to have a microprocessor onboard - no buffer or onboard step generator.  There's no D-sub, USB, or RJ45 connector - so there's no way to "talk" to it for programming purposes... because there's nothing to talk to.  It looks to me like a breakout board that provides some DC power for things like a tool touch-off sensor or limits.

The beige board also appears to be just passing the signals through.  I'm not familiar with the chips Andy pointed out, but a glance at a Ti datasheet indicates they basically act like voltage isolating relays.  Trigger input 1 with 5v and output 1 connects to COM and can handle up to 50v.  So those chips aren't changing or improving the step signals.

So it appears that there's nothing conditioning, buffering, or otherwise improving the stepgen accuracy between the PC and the stepper drives.

It'd be pretty easy to simply wire the PMDX directly to the stepper drives and see how well it works.

I wrote a more lengthy reply earlier and got an error posting it sorry. but what the hell i can give it a go for curiosity sake if nothing else. I can manage a tool touch off with a relay and an input im pretty sure if that and a speed change ( that ive not gotten to work yet anyway is all that is at stake) ive had to make alot of assumptions in the process and either confirming or eliminate them as I go so finding out if this board is really doing any better installed or removed is worth the hr it may take to do so is reasonable.

thanks again for the input and the more experienced veiw on things. ( hopefully I am thanking you latter) lol. but seriously many thanks to everybody already . ill post up my progress if nothing else as a what not to do with these rznc to dsp attempts, likely tho there aren't alot of them out here in the world or I could have found more examples.

As if the random bits of wire weren't a giveaway, based on the serial number, his PMDX-122 is a Rev C  - i.e. built between 2009 and 2013 (ish).

So certainly not an OEM installation from 2003-06.

It looks like the control system version of "I'm hungry, what's in the fridge that isn't furry?"

And yea, a new PMDX-126 with the required -107 spindle board will run about $240.  Ouch.