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How to convert a cnc interface that has +5,step and direction signals to signal common ground,step, direction

dmauch

New Member
I purchased a chinese cnc ethernet interface. The step motor signals are +5 , step pulse and direction pulse. However, my step motor drivers require a step pulse and direction pulse and uses common signal ground for the return path. Is there and easy way to convert the +5 signal return to common signal ground.
Here is the manual and you can see in section 2.2.1 https://www.makerstore.com.au/download/publications/ELEC-NS-U-Manual.pdf and 2.3 show how to wire the motor driver.
Here is the drivers that I intend to use
https://www.geckodrive.com/amfile/file/download/file_id/22/product_id/14/ Page 7 You'll see that pins 18-25 are all signal grounds for the 4 axis inputs.
 

Musicmanager

Active Member
I'm just in the process of setting up my CNC with an MVEM Controller … I'm using TB6600 drivers but it looks much the same to me.

I think you should be using Output 2 on your Gecko not Output 1 .. the pins are clearly labelled for step and direction .. .. .. .

What software are you planning to use for control .. Mach3 ?

S
 

dmauch

New Member
No that's not what I am looking at. The step pins and direction pins are pins 2-9 on the G540 those are INPUT pins. So the output pins on the NVEM connect to the G540 input pins. The output pins on the G540 are for relays not step and direction signal.
Does the TB6600 require +5 for the step and direction signals?
Dan
 

rjenkinsgb

Well-Known Member
Most Helpful Member
You need a 5V supply.

The handwheel interface on the CNC controller has 0V and +5V available, if you are not bothered about isolating the motor drivers from the controller.

Whether you use that or another PSU, connect PSU 0V to motor controller 0V/Common, PSU 5V to the +5V of the CNC controller motor interface connector and connect the step & direction signals straight through.
They may need pull-down resistors, eg. 4k7 or 1K on each step or direction line to 0V.
 

dmauch

New Member
Thanks that makes sense. I'll try it.
Dan


You need a 5V supply.

The handwheel interface on the CNC controller has 0V and +5V available, if you are not bothered about isolating the motor drivers from the controller.

Whether you use that or another PSU, connect PSU 0V to motor controller 0V/Common, PSU 5V to the +5V of the CNC controller motor interface connector and connect the step & direction signals straight through.
They may need pull-down resistors, eg. 4k7 or 1K on each step or direction line to 0V.
 

Musicmanager

Active Member
Hi Dan

I'm sorry, but I think you're missing my point .. .. .. the two items are essentially the same thing except that the Gecko has the stepper drivers built in, the NVEM uses external drivers such as the TB6600.

S
 

JimB

Super Moderator
Most Helpful Member
Dan

I am a user of a Gecko G540, there appears to be an incompatibility between the NVEM module and the G540.

The signals on the G540 DB25 connector are intended to be driven by an old style printer port on a PC.
All of the signals are referenced to 0v (GND).

The NVEM however uses a different technique.
+5v power is supplied from the NVEM to the stepper motor driver to provide excitation to whatever is inside the stepper driver (I guess an opto isolator).
The pulse and direction signals from the NVEM then pull down the other connection to the opto isolator(?) in the stepper driver.

Unless you want to build a suitable interface to connect between the G540 and the NVEM, I believe that they are incompatible.

JimB
 

ClydeCrashKop

Well-Known Member
Most Helpful Member
A 74LS240 inverting octal buffer chip would fix it for you. (Or opto-isolators)
 
Last edited:

dmauch

New Member
I took a look at the data sheet for the TB6600 it shows that the signal return path is signal ground. So you will have the same problem as I except that if you build your own you can add opto that will work with +5 and provide signal ground.

Dan

Hi Dan

I'm sorry, but I think you're missing my point .. .. .. the two items are essentially the same thing except that the Gecko has the stepper drivers built in, the NVEM uses external drivers such as the TB6600.

S
 

dmauch

New Member
Wow! What a surprise!. So far the best result was E. None of the above! Today I connected a Geckodrive G251 step and direction only to the Nvem and in mach3 pressed the tab key and clicked on the X axis and the motor ran without a signal ground! So I was really surprised as to where I got the signal ground from since I did'n't have it connected on the G251 and the NVEM. So I got out my trusty DVOM and checked to see if the the 48V power supply V-was connected to the output of the dc/dc 48/12 V DC converter. It was!. The 48V dc/dc converter to 12V powers the NVEM. And my G251 shares signal ground with power ground therefore the G251 signal ground was common to the dc/dc converter, the NVEM and the 48V power supply. Amazing! So using that same logic I am going to guess that when I wire up a breakout board between the G540 and the NVEM that it too will work with only step and direction signals but I will need to shift the power wires from the external power supply to the internal one.

Dan
 

Odie9

New Member
Dan,

Did you end up getting this to work? I have a G540 and one a Novusun interface card and can't get it to work. I breadboarded a DVR8825 and it worked without having the COM+ line hooked up at all, just the CP- and DIR- pins as step and direction in Mach3 but when I connect it to the G540 I can't get any motion. Any help greatly appreciated.

Odie9
 

JimB

Super Moderator
Most Helpful Member
Odie9

dmauch has not been logged on to the forum since 9th February.

JimB
 

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