Clearpath Servos with 1XD Expansion

[dc42]

I've checked the outputs from the 1XD board with 620 ohm load resistors, using your configuration (M569 P40.0 S0 R0 T2.7:2.7:2.7:2.7):

• The signal amplitude is 4.8V
• The step pulse width ls never less than 4.1us
• The smallest interval between step pulses I saw was more than 100us
• The end-of-step-to-direction-change hold time looks consistent at 8us, however direction changes are not very frequent so it's hard to be certain that there are no shorter ones
• The direction-to-step setup time appears to be very long indeed

Here's an example of a step with a direction change afterwards. The 'scope is looking at the STEP- (yellow) and DIR- (blue) output pins of the 1XD, with the 620 ohm load resistors connected between those outputs and the common +5V output.

PS:

1. The voltage across the 620 ohm resistor connected between Enable- and +5V is a little lower, 4.78V. This is expected, because that pin is not driven by a high current drive pin of the microcontroller. But it should still be enough, because few device providing 5V output signals would provide more than that.

2. Please confirm that you have connected the ClearPath A+/B+/Enable+ inputs to the common +5V pin on the 1XD board, and the ClearPath A-/B-/Enable- inputs to the individual output pins.

[jballard86]

@dc42 correct I have all positive pins connected to the 5v on the header with the dir, step, en pins. And those pins are directly attached to the servos.

The clear path manual does mention 5v minimum for the inputs and also states that less than that may work initially but will eventually not. I'm thinking the less than 5 volts is the issue here.

I mentioned the currents because the 1xd page mentions that they can only sink 10ma, and I assume that is through a 500ish ohm resistor. If that resistor is a 5% tolerance that would put the max current bellow 8ma.

[dc42]

I really don't think the voltage is the issue. There is no 5V level driver that really does supply the full 5V. A voltage drop of 0.2 to 0.4V is normal.

OTOH I understand the bit in the manual about not using differential drivers, because 5V differential drivers typically put out between 3V and 4V.

The STEP and DIR outputs of the 1XD can sink 20mA, and do not have a series resistor.

[dc42]

PS - you may wish to check the voltage across the Enable and DIR inputs of your servo drive, to check that there is nothing wrong with the 5V regulators on the 1XD boards.

[jballard86]

@dc42 ill check them when I get off work today, and I'll probably shoot teknic an email since they state 5-24v for signals and get their input.

I assume the 5v regulator also provides power to other ICs on the board?

Would it be possible to bodge a simple board that sends 12-24v to the servos and use a resistor divider back to the 1xd?

Is the 1xd schematic available yet, or will it be?

[dc42]

Here's the 1XD prototype schematic. We plan a few minor changes for the production version.

Duet3_EXB_1XD_Schematic_v0.4.pdf

[jballard86]

@dc42

4.99v on 40
4.97v on 41 Likely due to the R18 and R20 tolerances.

Did the same test with the servo encoders with the following results:

RAS 6.2	RAS 6.2		
3600 pulse/rev	3600 pulse/rev		
			
Servo Encoder at X0 Y0		Driver board position at X0 Y0	
A	B	                B41	B40
-12564	23112	               -49695	13499
-12289	23124	               -49695	13499
-12031	22945	               -49695	13499
			
no change with or without RAS			

Unless you have any other ideas I feel like the Clearpaths are not compatible with the 1XD board for some reason, Ill contact Teknic to see what their thoughts are.

[jballard86]

@dc42

After more research I have found multiple instances where Clearpath Servos are very picky about the signal voltage. Ive designed a small level shifter board and sent it off for a prototype run, I hope to have it in about a week or so. I will be shifting the signals to 12v.

Once the boards and components arrive Ill test the boards, then test them with the servos and ill update.

[Bondtech]

@jballard86 Did you manage to find a solution? If you did what did you change?

[DOP]

@dc42 @jballard86 Either of you ever figure this out yet? i just setup with 2 clearpath servos i see 0 hiccups but the layer shifts are real! i'm on version RRF 3.2 via duet3 + Pi4 SBC.

[DOP]

For others who find this thread: I just installed beta 3.3 and it's working correctly now, looks like root cause was in can communications.

[jbergene]

@dop and @jballard86 . Have any of you managed to produce a good looking print yet?
if yes What were the T timings you ended up using?

Best regards
John Henrik Bergene

[jballard86]

@dop I fixed it by abandoning it and going with a different hardware solution. My assumption after lots of trouble shooting is that the clearpaths en/stp/dir signals needed to sink more current than the 1xd could provide, or that it was a CAN issue. I ended up developing my own board that worked flawlessly.

[jballard86]

@dop said in Clearpath Servos with 1XD Expansion:

For others who find this thread: I just installed beta 3.3 and it's working correctly now, looks like root cause was in can communications.

If it was an issue in CAN, id assume that issue has been in all of their products that utilize CAN. its unfortunate that they left bugs like these in their code for so long unnoticed.

[atlas_Clark]

@jballard86 I am currently embarking on a project implementing the ClearPath SD servos with a duet 3 and 1XD and was wondering if you would be able to provide any wiring advice or images? I've followed the documentation as best I can for wiring the step/dir/en to the 1XD with no luck and this post is one of the very few demonstrating exactly what I am attempting to create.

[alankilian]

This looks like all you should need for wiring information and timing.

However I don't believe the original poster got these servos working correctly. (I may be reading it wrong.)

@dc42 said in Clearpath Servos with 1XD Expansion:

I've checked the outputs from the 1XD board with 620 ohm load resistors, using your configuration (M569 P40.0 S0 R0 T2.7:2.7:2.7:2.7):

• The signal amplitude is 4.8V
• The step pulse width ls never less than 4.1us
• The smallest interval between step pulses I saw was more than 100us
• The end-of-step-to-direction-change hold time looks consistent at 8us, however direction changes are not very frequent so it's hard to be certain that there are no shorter ones
• The direction-to-step setup time appears to be very long indeed

Here's an example of a step with a direction change afterwards. The 'scope is looking at the STEP- (yellow) and DIR- (blue) output pins of the 1XD, with the 620 ohm load resistors connected between those outputs and the common +5V output.

PS:

1. The voltage across the 620 ohm resistor connected between Enable- and +5V is a little lower, 4.78V. This is expected, because that pin is not driven by a high current drive pin of the microcontroller. But it should still be enough, because few device providing 5V output signals would provide more than that.

2. Please confirm that you have connected the ClearPath A+/B+/Enable+ inputs to the common +5V pin on the 1XD board, and the ClearPath A-/B-/Enable- inputs to the individual output pins.

[atlas_Clark]

This post is deleted!

[chine]

Any update on this? Did anyone get their setup working?
I saw Pantheon Design is using clearpath on their new printer but it sounds like they created their own hardware to use duet/clearpath.

Thanks

[Edkirk]

@chine Several years ago I built a Corexy to test Clearpath Servos, I had no problems. Absolutely awesome performance. Looking through the above post I didn’t see any mention of power voltage and current to power the servos. I used a power supply from Clearpath for Servo power. I was initially concerned about signal voltage from the duet board for step/direction but there was no problem. I set Clearpath resolution to get close to my original steps per mm in config.g. I found the servos were over kill for a 3D printer, they are no better then the signal from the board just producing slightly better then a good stepper motor. They are very quiet. I transplanted the servos to my CNC router where I needed the extra power. Photo of the original test printer.
Ed Kirk

[SignPostMan]

@jballard86 Do you have these boards available for sale? I have developed my machine around Clear Path servos without knowing this problem until finished with the project. Looking for the easiest answer to solve.