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Author Topic: Has anyone actually got a C11 to control a KB speed control via Mach?  (Read 17091 times)

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I must be a complete idiot because I can't.  I have Mach neatly switching the KB power on & off via M3 commands or clicking the onscreen "spindle" button.  If I leave the manual pot connected, the KB varies the speed of the Baldor 3/4 hp motor beautifully (yay KB!)  If I take off the pot & connect the C11 to the KB, the motor instantly spins up to a much higher top speed with no control via "S" commands.  No Mach config changes make any difference.

The C11 manual (to me) is vague but the C6/KB hookup section has more verbage on hooking up to a KB and I assume the 0-10V analog circuits are the same in the 2 boards.  My interpretation of the C11 instructions is that the pot is to be removed and the C11 0-10V analog outputs connect to the P1 & P2 terminals on the KB which leaves the P3 terminal open.  The C6 instructions (pasted below) to me imply that the outputs are connected to the pot terminals.  Can that be true???

"These are the steps for replacing a potentiometer:
1. Measure the voltage difference between P1 and P3. Make sure it measures
under +12vdc.
2. Fine tune the analog output to the output voltage you got from step 1.
3. Connect the ground from the analog output to the ground of the
potentiometer (P1).
4. Connect the analog output to the wiper connection of the potentiometer
If the reference voltage from pot is between +10 and 12vdc, you can use it to
power the analog circuit (not for the C6, because the relays might draw too much
power). In this case, connect P1 to the ground of the power terminal, and P3 to the
+12vdc power connector."

I checked the voltage across the KB P1/P2 terminals with the pot attached & turned up to max, motor running at full chat and get 3.5VDC.  I checked the voltage at the gnd/0-10V outputs on the C11 (with nothing attached) and it varies up & down in concert with varying S commands from Mach.  I set it to 3.5V max with the onboard trim pot.  I know, not what the inst says but I had to try something to slow things down!

When the pot is removed from the KB and the 2 leads are connected from the C11, the voltage across P1 & P2 is locked on approx 6.5 volts, no matter what is commanded by Mach.

Somebody please smack me up side d'head and clear up my stoopidness!!

Milton from Tennessee ya'll.
I may have posted this in the wrong section since it's probably not "General Mach Diccussion" related and is a hardware question.  Should it be moved to another section and if so, how do I do that?

Milton from Tennessee ya'll.

Offline Hood

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I think its fine here, more chance of people seeing it. You may however get a quicker response from Arturo.

Offline Vogavt

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Not me but I'm attempting the same scenario.

Waiting now of replacement chips for the c11 from Arturo. Seems he's out of stock on one particular IC needed for the set but he didn't say when it was due to come in.

On hold for now. Once I get things running I'll let you know how mine is setup.

Actually now looking into the Gecko 540 and a higher Amp & Voltage power supply too.

I may disband the whole cnc4pc thing. Well see.

If you get it figured out before me, I'd appreciate the reciprocity of the details!


I'll definitely pass along any info, good or bad.

I've decided to back off the speed control issue for now since further uneducated fiddling around may let out some smoke.  I still have a lot of mechanical chores to work on to get this lathe up & running and manual speed control via manual pot will do fine.

I emailed Arturo a couple weeks ago and it must've gotten lost or he's on vacation...no biggie.  I'll try him again later.  He's been quick with answers previously.


Collierville, TN
Milton from Tennessee ya'll.
Which KB controller are you using?  On my Novamill I have a KBWM240 running a Baldor .5 hp motor, but as far as I can see the KB controller's pot must be floating around relative to earth since there is no transformer or dc-dc converter inside the KB to isolate it from mains voltage.  I decided that in order to control the speed from Mach 3 I will need to opto-isolate the variable duty-cycle output and smooth it on the "KB" side of the isolator.  If you try connecting direct, goodness knows what is happening.

Offline Vogavt

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I decided that in order to control the speed from Mach 3 I will need to opto-isolate the variable duty-cycle output and smooth it on the "KB" side of the isolator.

"Opto-isonlate" Are you saying that you need another board? The c11 has that already.

"smooth in on the KB side" How?

Sorry I not the brightest when it comes to electronics (except when that dreadful flash of brightness happens, and in my case it usually means a bad thing if you get my drift). LOL!
John, I'm not electronically savvy enough to follow what you've said above but thanks for the input.;D

I have a KBIC-120 controller.  I would think all the KB's of that basic design share the same pot connections and operation.

The C11's speed control output is definitely DC, adjustable between 0 - 10V.  The C11 manual specifically states that it will control KB and similar type DC motor speed controllers by replacing their manual pots.  There must be something I'm missing in the hookup & calibration.  I emailed Arturo again yesterday so hopefully he can clear up my ignance.
Milton from Tennessee ya'll.
Well, apologies that I wasn't familiar with the C11 BoB when I first posted.  On looking at its manual (which is not entirely clear on this matter) the 0 - 10v output is internally opto-isolated, that is, it has two outputs between which it will output a voltage variable in this range, and these outputs are electrically isolated from ground so they can safely be connected to the KBIC. 

Looking at the KBIC manual, I think it is essentially the same as my controller except that mine comes in a metal box with control pot and mains switch.  However these controllers are NOT grounded, so the "0 volts" line at one end of the pot will be bouncing round at up to mains voltage, hence the need to opto-isolate the control input.

For the C11 to generate that isolated 0-10v ouput, it has to have an internal source of more than 10 volts that is itself isolated from ground, and I think it must have an internal floating dc-dc converter incorporating an isolating transformer to do this.  The C11 manual does say that for the function to work a +12 volt 20 mA supply for the function to operate (see page 15), which would be supplying the on-board converter.  Do you have this supply connected?  If it isn't then you would get anomalous behaviour.  See page 18 of the manual for where to connect it.  As far as I can see all the rest of the C11 only needs a +5 volts supply.  If you need to generate +12 volts then a small regulator off the stepper motor supply should do it.  My BoB on my lathe runs from the stepper supply (about 40v) which it reduces to 12v then 5v.
Thanks John, I can't tell you how much your knowledgeable input is appreciated!  I do OK with auto DC circuits and simple electronics but for some reason the verbiage in the C11 (and C6) manuals re: speed control hookup zings right over my head.

Yes, I have a completely separate 12VDC 1 amp power supply connected to the proper 12V inputs on the C11.  If I connect a voltmeter across the Gnd and 0-10V outputs on the C11 with nothing else connected, I get varying voltages corresponding with various S commands from within Mach.  To my way of thinking, that verifies that the P/Port pin hookup and the config settings in Mach are OK.  It's just getting that varying voltage connected to the KB in a way that makes it happy is the problem.

My simpleton logic tells me that if the KB works properly with 3 wires connected to a pot, there should be 3 wires going to the C11....BUT the C11 outputs a variable voltage, not a variable resistance; so there goes simpleton theory. ;D  Don't they have a correspondence course for that?  "Simpleton Electronics Theory" ::)
Milton from Tennessee ya'll.