Hi, again...  I've rearranged things and put a new computer into the system but I'm still having trouble.  The new cable to the motors is 4 conductor plus shield and the shields are star grounded to the Geckdrive power supply minus terminal.  I'm still getting offsetting issues.  I'll post some pics of the current setup.  Please tell me if there is anything obvious...
Don

This is the current configuration of the system.

Hi Don,

Can you now use your special shielded cable directly from the PP to the Geckos to bypass the breakout board?

Are the signal cables to the Geckos (step and direction) shielded and grounded at the breakout board end? Looks so on the picture, but hard to tell exactly

Dan

The new cable to the motors is 4 conductor plus shield and the shields are star grounded to the Geckdrive power supply minus terminal.

Are they grounded at one (Gecko) end or grounded at both ends (Gecko and motor)?

Btw - you could also try putting a large film capacitor (say 0.1 uF) across the big electrolytic.

Cheers

I could try it...  I've come across a page on Gecko's website on dealing with RFI issues.  It suggests using a 5 conductor cable with the shield.  My step and direction cables are shielded and the shields are attached to the star ground on the power supply.  Gecko suggests grounding the motor case with the 5th wire to the power supply ground and connecting the shield to the electrical box only at that end.  I'll try that as soon as I can.  I'll try using some coax with the shields of the 4 conductor and coax tied together.  
Sorry about the rats nest appearance, there are a LOT of ground connections...  Thanks, Don

rcaffin,  all the shielded cables, including the signals are only grounded at the star connection on the power supply capacitor.  I haven't grounded the chassis yet.  I'll try that tommorow evening and see what it does before I try to implement the Gecko suggestion.   Don

rcaffin,  all the shielded cables, including the signals are only grounded at the star connection on the power supply capacitor.  I haven't grounded the chassis yet.  I'll try that tommorow evening and see what it does before I try to implement the Gecko suggestion.   Don

It's Roger. :-)

Anyhow, my advice is to NOT ground cables at both ends. I assume the motors are grounded to the chassis, and the power supply *should* be grounded to the chassis as well, but I would NOT run any parallel earth connections. The potential for ground loops is real and bad. For this reason I have reservations about the Gecko 5-way cable idea. Actually, running a serious earth cable in with Step/Dir signal lines strikes me as really bad news.

I admire the star connection on the electro, but it must be a bit of a problem managing it. I know we can buy very heavy brass terminal bars with something like 16+ holes for mains connections in switchboards and junction boxes. I would probably use one of those for the single earth point instead. Ratings of 100s of Amps.

Cheers

Hi, Roger,  Thanks for the suggestions.  I too have reservations about the additional grounding of the motor case for the same reasons you list.  I'm trying to keep every thing single connected so there wont be paralleled circuits.  The motors are indeed bolted to the aluminum mounting plates on the aluminum brackets on the machine elements and have electrical continuity to the chassis.  I don't know how running an additional ground would help unless they were electrically isolated, which would be difficult to achieve.  The capacitor has #10- 32 threaded posts so I was able to get a longer screw to lock everything down.  I haven't gotten to work on the project this weekend yet but I'm going to try to ground the chassis first.  I'll see if that changes the running behavior.  Thanks
Don

I put a small jumper from the negative terminal to the chassis Aluminum plate, and it had no effect...  Hmmm.  What am I missing, here?
Don

I put a small jumper from the negative terminal to the chassis Aluminum plate, and it had no effect...  Hmmm.  What am I missing, here?
Don

You know, debugging earth problems from the other side of the planet does present problems! So pls forgive my basic Qs.

I can see 4 wires from the +ve terminal on the electro, apparently going to each of the 4 Geckos?
I can see 12 black wires from the -ve terminal, and I am not sure where they all go. For sure, 4 go to the Geckos, and perhaps 4 more go to the screens on the motor power cables? But the remaining 4? Step/Dir cable screens to the SimpleStepper?

Now, the earth strap you put in. Can you remove it and check to see whether there already is continuity between the -ve terminal on the electro and the chassis? If adding a strap had no effect, you may already have a connection - dunno where.

Are you using the SimpleStepper with a BoB, or is it all connected directly? I can't tell. Off-hand, I don't know whether all your Step/Dir signals have optical isolation, which is HIGHLY desirable.

Btw - nice layout. I wish mine was that easy to access.

Cheers