7i76 analog spindle power options

Hi all, I'm running a very similar motor speed controller in my Sherline machine (Model KBLC-240DS / KBIC series). I've read through its manual and found that it too can be controlled with an isolated analog reference voltage (0-7 VDC). Searching around I also came across the Soigeneris AN-01 tutorial, which documents how to hook this up to the G540 VFD Output. I'm planning to do the same thing to the 7i76 board. I believe the basic connections will be:
1. Spindle - to P1 (low)
2. Spindle Out to P2 (wiper)
3. Spindle + to P3 (high)
The MIN and MAX pots may need some tuning but I'll let you guys know if I run into any issues.

Read the manual again and double check the connections. I am sure you will not need P1 and P3. The KBMM uses P2 and F- in voltage following mode. And in this mode it bypasses the min and Max pots. The kbmm is rated 0-9v but could actually take alot more in this mode. At least with my setup the input voltage was roughly 1/10th out put. So at 9v I got 90v out. 13v got 130v out. I wouldn't run it that high though.

Hi Michael,
You are correct. Section 9.4 of the KBIC manual states that the reference voltage (0-7 VDC) is connected to P2 (+) and F-.
The KBIC manual doesn't say that F- and P1 is interchangeable but the KBMM manual does state on page 15 that Terminal “F-” may be used in lieu of Terminal “P1”. I'll look more into this.

P1 and P3 is not required, it's just that the voltage between P1 and P3 can also be fed to Spindle+ and Spindle- on the 7i76 instead of using a separate power supply (if i'm reading the Soigeneris document correctly)


By the way, what do you recommend for the spindle interface cable? I'm thinking shielded CAT5 cable should do the trick...

From personal experience P1 and P3 will not drive enough amps through the 7i76 to power the spindle. I learned this the hard way. I used a 12v wall wort. I am not familiar with the G540 but if it supplies a VFD and can drive enough amps then it should work. I do not remember the number of miliamps that the 7i76 needs but I seem to recall it was more than you would guess. You will know it isn't working if you are not getting full voltage when you have a full scale spindle speed command in Linux. Cat5 shielded should work fine.

Ok, thanks for the heads up. I think my PC's power supply has separate 12VDC output as well that I can use for this function. There are 5 other pins left on the TB4 connector (NC, SPINDLE ENA-, SPINDLE ENA+, SPINDLE DIR-, SPINDLE DIR+). I'm not sure if I need any of these at this stage (going through PNCconf setup) to get the spindle motor working? Not trying to do threading or anything like that right now, just trying to have basic speed control from Linuxcnc to the lathe's spindle motor.

Don't use a PC power supply to power a KBIC speed control interface, the interface is "hot"
(not isolated from line voltage) and the PC power supply common pin is connected to chassis ground,
so you would likely damage the KBIC/PC or yourself doing this.

A isolated wall wart can be used instead, and you need to be aware that if connected to a KBIC speed control,
all the 7I76 spindle connections need to be treated as carrying line voltage.

No you will not need those. They are simple switches to control direction, and on and off.

Ok, so I finally got a 12V power adapter (1.5A). My TB4 spindle connector is hooked up like this:
Pin 1 connected to -12V and F- (from KBIC controller)
Pin 2 connected to P2 (from KBIC controller)
Pin 3 connected to +12V

Went through PncConf and got to the Spindle motor page and put in 7V max voltage and 5600 max RPM. Opened up the Open Loop Test and tried the jog buttons + and -. I was thinking that spindle move should start spinning at this point but I have no motion from the motor. Did I mess up somewhere?

I did not have any luck jogging an axis or spindle while Pncconf either. Complete the configuration and then try running it. I would disconnect the KBIC altogether for testing. Just run the power supply to the 7i76. for testing set up a meter to read the voltage between spinout and and spin -. That way if you have the scale off in ini file then you won't be worried about what the KBIC is going to do.

The bottom of your ini file should look something like this:
#********************
# Spindle
#********************
[SPINDLE_9]
P = 0.0
I = 0.0
D = 0.0
FF0 = 1.0
FF1 = 0.0
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
MAX_OUTPUT = 7000
ENCODER_SCALE = 5000.0
OUTPUT_SCALE = 7000
OUTPUT_MIN_LIMIT = 0
OUTPUT_MAX_LIMIT = 6000

The output of the 7i76 spindle can be scaled a number of ways. I did mine based on RPM because it ended up being easier to wrap my head around. If your power supply has a measured output of 12v and you only want to have a max of 7v then you can make yours out to look this way:

#********************
# Spindle
#********************
[SPINDLE_9]
P = 0.0
I = 0.0
D = 0.0
FF0 = 1.0
FF1 = 0.0
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
MAX_OUTPUT = 12
ENCODER_SCALE = 5000.0
OUTPUT_SCALE = 12
OUTPUT_MIN_LIMIT = 0
OUTPUT_MAX_LIMIT = 7

That should limit your output. Change your ini file to this and then run a m3 s5600 command. You should get 7v at spinout.