Mesa/Pico/PMDX

Tom wrote:

Let's see if I have this correct.

I could source a Pico Universal Stepper Controller and 4 x Gecko G203v/G213v (has 2 * X-axis steppers). The Pico could drive both x-axis steppers by simply connecting x step and direction to both G213v drivers.

It appears the Pico USC could control the speed of my Hitachi M12VC router with a spindle DAC board and a SuperPID.

The USC appears to have inputs for home, limit, and e-stop switches.

yes, and yes.

OK. What about a pendant? Could that be done with a second EPP or would it make sense to go for a Mesa 6i25 so I have plenty of I/O? As I understand it, USB pendants are not currently supported?

Much better is to use the native I/O of the USC, and build or adapt a pendant along the lines of
pico-systems.com/pendant.html
Please ignore the ugly pendant, my 2nd version looks better. You can also use a cnc4pc
pendant, but I wouldn't pay their high price. And, there ARE now USB pendants that
are supported by LinuxCNC. Just scan this message list.

Jon

Tom wrote:

One more thing.

It appears the Pico USC can take encoder input. What does it do with that input? Does it just e-stop the machine when it detects a problem?

No. If the external encoder input is enabled (on an axis by axis basis) then it closes the
positioning loop using this input, in preference over counting the steps issued.
The problem with steppers is you can't ask them to "try harder" so closed-loop
operation doesn't have the same advantages as a servo system. But, you
can set up following error limits in the .ini file to decide under what conditions an
error is declared. For instance you can have a sliding scale proportional to
velocity, so more error is permitted at higher speed.

My steppers (HobbyCNC NEMA23) are single shaft so they won't accept an encoder but I should be able to add an encoder to the gantry rack and have the same thing. Correct? Is there any way I could use two encoders on the x-axis to make sure the two steppers on the x-axis do not go out of sync and rack the gantry?

No, it can't accept multiple feedback sources. But, you could set the machine
up with two X axes, one driving each motor. Then, you have the slight
issue of how you home the two sides of the gantry. They will always be
slightly out of square at startup, when homing, you can arrange for the first
side that hits the home switch to pause and wait for the other side to
catch up. This homing to square the gantry is an issue that has come
up MANY, MANY times, and there still is not consensus on how BEST to
do it.

Jon

I'll update this thread for future folks who find it with a search.

I picked up a Pico USC. Jon has been great and he is shipping it USPS. That is appreciated.

I have a set of Gecko G203v drivers on order.

The PSU is Antek 1000W - 65V (PS-10N63R5R12)

I've also got a bunch of other miscellany ordered like din rails, SSR, connectors, etc.

Now I have to figure out what to put these guts into. Rack mount kit boxes seem kind of spendy. I was thinking of repurposing an old PC case. Any advice from the Canadians? My Dad has a fully equipped sheet metal shop. Maybe I should build something custom?