Step Frequency

[Commotion]

I encountered something when testing the leadshine dcs810 drivers to see if they would run the dc servos in my lathe. I connected them up to my version 2 acorn with the terminal connections. After scratching my head for a bit I remembered I had my acorn set to 400kHz so I dropped it to 200kHz and then the servo worked.

A week or so later I have connected the servo up to a version 3 acorn and wired it up to the db25 connector as per the wiring diagram. I had it set to 200kHz but the motor wouldn’t move. After trying a bunch of things I set parameter 968 to 12 for 100kHz and then the servo worked. Is there something different between the waveform generation of the version 2 and 3 ie the wave duration is less for the same max frequency or would the difference lie in going to the db25 connector? I notice in another post here it’s suggested to change max frequency to 100kHz. It’s not really a concern with this particular machine as the servos only have 500 line encoders and they are direct coupled so 100kHz gives me 3000rpm and 6m/min but I am working on another retrofit and this May cause me dramas.

[cnckeith]

main difference between the two.

db25 uses 5 volts

screw terminals use 24 volts

with the leadshines, in general they don't always the take a step frequency that they claim they can.

also, running over 200 khz requires proper wiring, shielding and grounding to work reliably. there are older posts on this subject.

[Gary Campbell]

If you read the manual, it shows that the inputs require 7 to 15 volt signal voltage and also shows a connection for a resistor value for connection to the open collector header. I would use that diagram, with appropriate resistors and start at 100khtz step freq.

[Commotion]

Hi Kieth, yes some of the older post we mine with issues I had with leadshine ac servo drives.

Can u explain the 5v, 24v thing to me as I thought the acorn just closed the circuit as the 5v is supplied by a separate power supply.

Gary, the manual only requires a resistor when Vcc is greater than 5v. I have a separate power supply providing 5v.

My curiosity was why it would accept 200kHz on the older acorn but not the newer one. The only other difference was being connected to db25. What ever it is, it may also be why I run 400kHz setting on the ac servos on the old acorn without any issues. I have my rapids set so I don’t exceed 200kHz but has half the wave length at 400kHz than 200kHz as I understand it.

[cnckeith]

the Acorn db25 step and direction output is designed for use with 5 VDC stepper drives.

the Acorn screw terminals are designed for use with AC servo drives that accept 24 VDC for the step and direction signal and stepper drives that use higher step and direction voltages than 5 vdc , such as 12 VDC (for non 24 vdc cases you would be using a resistor)

in general you want to run stepper drives at 100Khz , some models will accept and run at 200 Khz, even with those run them at 100 khz to test with , get everything else working well and firgured out.. then and only then try and go to 200 khz.

some stepper drives models claim to accept a shorter pulse (say around 400khz) but in reality they do not. some leadshine manuals that i've read even contradict themselves in one place saying that the max step freq is 400 khz, but in another section of the manual say that the max pulse width accepted has to be wider than that.... i have no idea why they do that.

every AC drive that i have tested runs well on 400 Khz, yaskawa, delta, estun and DMM.
others have reported on the forum about Panasonic and Teco step rates that worked for them.

[Commotion]

Thanks for the explanation Keith.

I can confirm that my leadshine acs806 drives accepted 400kHz option but has signal noise issues. instead of addressing my cabling issue I just changed electronic gear ratio and ran at lower frequency. It claims 600kHz and requires min 0.85us duration.

The dcs810v2 drive claims up to 500kHz and requires 1.0us duration. I was a lot more thorough in my cabling on the dcs drive so maybe for curiosity sake I’ll connect it up to the terminals and see if it runs a higher frequency (not that it needs it on this install so I’ll prob just go back to run db25 for neatness).

I will update with what I find.