Would you be willing to try something for me? Remove the UPS. Unplug the ribbon cable(s) from the SmoothStepper and make sure it is powered by the USB cable, not an external supply. This should still let Mach connect to the SS, with Mach talking to the SS (red LED blinking) try your shop heater and see if the SS/PC communication is still disrupted.

I just gained operational success when I moved the heater to a different breaker in my shops load center. 

I will restore the electric config that causes problems and give it a try for you though.  I suppose I will also need to rejumper teh SS board to use USB power too, right?

-dg

If you would try it that would be great. You might try it on USB power and external power to see if there is a difference. When you are testing on USB power you might want to pull the external power connector off. I'm just trying to determine if the noise is getting to the SS through the ribbon cables, the power cable, or the USB cable.

Also, if it seems to work on USB power with the ribbon cable(s) dissconnect from the SS, you might try it again with USB power and the ribbon cables connected.

Thanks!

By "ribbon cables" I am guessing you refer to the port 1 and port 2 cables coming off the PMDX-126 BOB to the smoothstepper. 

I am not sure what Steve is doing to produce 5v on his BOB, probably something like a a LM7805 or the like. 

There is a fairly small transformer connected to 115VAC, a pair of small surface mount bridge rectifiers, some small can caps, and two three pin regulator chips... pretty standard power supply design. 

Are you hooking the 5V from the BOB to the 5V external power terminals up by the USB connector? Or, are you just using the Port1 & Port 2 cables themselves?

Just the port 1 and port 2 cables.  I have thought about building a little 5v external supply using an ATX computer power supply, putting a 10ohm 10W resistor onto the output to provide the nessessary minimum load for proper regulation and providing terminal posts etc. as accessories.  With that I suppose I *could* power the SS from a well regulated external supply. 

Cart before the horse though, would like to identify where the noise impulse is coming from first, might be from the computer side.  Will be working the procedure you requested tomight after work, did not get out to the shop yesterday hardly at all, I had evening meetings to take care of.

Just the port 1 and port 2 cables.

I'm not sure that is such a great idea. The connector to supply an external 5V that is on the SS board, located up by the USB connector has some filtering built into it. If you are powering the SS through the BOB than if your BOBs power supply is picking up noise you are just transferring that noise directly to the SS itself. As far as an external power supply I would not mess with getting a PC supply to work, that is a very inefficient way of doing things. I have small 5V supplies here: http://www.soigeneris.com/MeanWell_PS_05_Power_Supplies-details.aspx (my website) that work very well with the SmoothStepper and do not have a minimum load requirement.

I agree, not all that efficient, however I have the stuff to do the ATX PSU conversion on hand, and it's money I don't have to spend. 

interesting comment about not using the BOB power via the ribbon cables.  The BOB docs say that it's fine to do so, but maybe not int his case.  I think I will try USB power first, then eventually set up the external 5V -- I can use a utility source of 5V for other stuff anyway.