Mesa 7i96 to spindle FWD/REV control

I am use a 7i96 as 4-axis + PWM/DIR to control the spindle of a CNC milling machine. The CNC milling machine has a FWD/REV manual switch which I want to be replaced by two relays as suggested in Franco's youtube channel. The connection scheme is shown in the attached the picture.

Is the following connection from 7i96 to relay module correct?

Dir4+ ---- input of relay 1
Dir4- ---- input of relay 2
GND ---- S/S of relay module

Sorry for the novice question.
mhd325ic

I used your conconfiguration tool. Thanks very much and I get xyz axis working like a charm. Now I am thinking retrofit to 7i96 spindle control.

My milling machine's spindle needs 0-5v analog voltage to control the RPM. My plan is to convert PWM signal by a PWM2DC module in order to replace the potentiometer outputs. And DIR signal is used to control switchover relays.

Thanks pointing out that voltage 4 may not be 5V pulse.

What is the best approach to retrofit 7i96 to my spindle control?

Thanks in advance!
Mhd325ic

Thank you for pointing to this post. This post and the mini lathe project are similar to my situation. It seems a good template for me to try and errors

After reading those posts, my plan is to use PMW4 for spindle variable voltage input and two 7i96 outputs for FWD/REV input.

Please point me out if I misunderstood the information. I will give it a try and posted back.

I use a cheap PWM2DC module to convert PMW4 signal to 0-5v analogy voltage and an opto-isolated relay module is used to implement digital switchover. Without connect to the milling machine spindle control, the output voltage and FW / REV switch over works as expected when measured with a multimeter. The modules that I used are and .


However, it trigged GFCI breaker when it connect to the milling machine. Now I am guessing that the problem is PMW2DC module which don't have opto-isolator. Is my guess correct?

Thanks for the help from you and PCW. I got the logic correct. With a SPINX1 card, now 7i96 can control spindle actions of setup speed and directions.

The problem that I am facing is that there are about 25% difference on linuxcnc rpm and spindle rpm.

Is there any way to set scale using 7i96 configuration tool?

I dont know about the config tool but you can certainly change
the 7I96 PWM scale in the hal or ini file

I did a calibration of actual rpm vs setted rpm in linuxcnc. The result is shown in the attached picture: in the setted rpm range of 0-2000, the spindle rpm of spindle is close to linear. If we can map the PWM duty range 0-0.8 to the spindle rpm 0-2500, the spindle speed control accuracy will be improved largely.

How to do it in the linuxcnc?