I am trying to interface a Kflop and Kanalog to EN-204 brushless servo drives.   While these drives do have torque and velocity modes with +/-10V input, I want to run them for now in pulse mode because they are already functioning perfectly with the motors they are connected to.

The en-204 diagram on the step and direction input shows an internal 350 ohm pullup to the 5V logic of the EN-204 drive.

Since I have the Kanalog board connected to JP7, I must use the pulse outputs on JP4 and JP6 to control my four drives (x,y,z, and theta).   These are 3.3V LVTTL.

Everything should be fine on the high side since the drive pulls up to 5V internally, but this relatively low resistance pullup means the IO on the Kflop JP4 or JP6 connector must sink around 15mA (5V/350 ohm).   I am not able to find any information in the Kflop manuals on the current source/sink capacity for these connectors.

Thanks,

Rick

Hi Rick,

Unfortunately the first 8 I/O on JP4 and JP6 have 150 Ohm pull down resistors.  So there is only one Step/Dir set on each connector without the pull down resistors to work as open collector drivers.

The source/sink capability of all the KFLOP I/O are +/-16ma.  The I/O are also diode clamped to the 3.3V Power Supply (limits the high level to ~ 3.8V).

I Googled and read somewhere that these drives single ended inputs require 3.5V for a high and less than 1.5V for low.  So the low should not be a problem but the high level might only be as high as ~3.1V.

The best approach would probably be to add line driver modules.  Such as:
https://cnc4pc.com/differential-line-driver.html#prodtabs-3

I suppose with some resistor dividers you could also create a threshold of ~ 1.2V and use the drives differential inputs.

Regards
TK

 

I am trying to interface a Kflop and Kanalog to EN-204 brushless servo drives.   While these drives do have torque and velocity modes with +/-10V input, I want to run them for now in pulse mode because they are already functioning perfectly with the motors they are connected to.

The en-204 diagram on the step and direction input shows an internal 350 ohm pullup to the 5V logic of the EN-204 drive.

Since I have the Kanalog board connected to JP7, I must use the pulse outputs on JP4 and JP6 to control my four drives (x,y,z, and theta).   These are 3.3V LVTTL.

Everything should be fine on the high side since the drive pulls up to 5V internally, but this relatively low resistance pullup means the IO on the Kflop JP4 or JP6 connector must sink around 15mA (5V/350 ohm).   I am not able to find any information in the Kflop manuals on the current source/sink capacity for these connectors.

Thanks,

Rick

Yes, I found mention in a post that the IO could source/sink 16mA and I went ahead and wired it up, works fine.

I think the high level is ok because the drive pulls it up to 5 volts through the 350 ohm resistor, thus when the Kflop drives the output to 3V, it likely is seeing well above that to whatever logic is connected to the single ended inputs.   Whatever, it works, but I will keep it in mind if down the road I have some mysterious missing steps :-)

Actually, when I get a chance I will hook up the scope to the drive input and see exactly how high the line into the EN-204 is going when the Kflop drives its side high.