Controlling A DC Brushed Motor

Hello!

I have a small milling machine and will be swapping to a 3HP DC motor, with a new controller (which takes 220Vac instead of the stock motor's 110Vac). The controller is a KBMM-225D, which you can see here: www.galco.com/buy/KB-Electronics/KBMM-22...C6_b8CFWho7Aod4TYAVw

I have been using LinuxCNC for a year or two but have never done any customizing, so I am seeking guidance on how to proceed with a few of my goals for this new motor. I am not looking for you guys to solve these problems for me, but am hoping some of you can point me in the right direction.

1. I would like LinuxCNC to know the spindle RPM. From the factory, there is an index ring with 16 slots (16 pulses/rev) that are read by a sensor for the RPM readout. I'm not sure if this ring can be used, or if I need a 1 pulse/rev ring for the software. Does this signal go right to the break out board (mine is a C11)?

2. If the spindle RPM drops (even something like 20%) due to sudden load (crash) I would like LinuxCNC to ESTOP.

3. Have LinuxCNC control the on/off of the spindle, and set the spindle speed. The KBMM says "An isolated 0 - 9 Volt DC analog signal input can be used to control motor speed in lieu of the Main Speed Potentiometer" so I assume I should be able to get this working.

I appreciate any help you guys can offer. If you have used the KBMM for any of this, even better

rusmannx wrote:

Hello!

I have a small milling machine and will be swapping to a 3HP DC motor, with a new controller (which takes 220Vac instead of the stock motor's 110Vac). The controller is a KBMM-225D, which you can see here: www.galco.com/buy/KB-Electronics/KBMM-22...C6_b8CFWho7Aod4TYAVw

The main warning is the KB motor drives are NOT isolated from the mains. So, anything that sends a speed control
signal to the KB drive needs to be isolated. You can probably build an isolator with an optocoupler and
a few components. Then, you'd have your CNC control send a pulse width modulated signal to the
optocoupler.

Jon

Thanks for the heads up, I'll start doing some research.

Well I've been doing some reading and am realizing that it may be a pain to get my C11 breakout board to talk to the KBMM board. I think I'll skip that part for now, but I would still like to get LinuxCNC to read the spindle so I can have an onscreen tach.

This thread is turning into a bit of a one man show, but it looks like I can use the CNC4PC C6 to control the spindle speed (and it's optoisolated) and the C3 to send a tachometer signal to my C11 breakout board.

Thanks Rus!

andypugh wrote:

Mesa have a device that might help:
store.mesanet.com/index.php?route=produc...spinx&product_id=205

Basically an isolated potentiometer replacement.

The onscreen Tach should be fairly trivial. Multiple slots per rev is no problem, you just need to set the encoder scale correctly. With only a single slot you would need to "setp encoder.N.counter-mode 1".

An index slot would help if you want to do rigid tapping, but otherwise doesn't add anything.

Thanks, that's a great link!
I haven't even considered rigid tapping, so I'll look into that. Thanks again.