Messages

1

General Mach Discussion / Re: Mach3 Output For DC Motor Control

« on: August 04, 2013, 10:07:03 AM »

Hi Ray,

I understand.

Could be the reason why no one ( as far as I know ) drives directly from Mach3.

I wonder what the lowest usable base frequency is?

What are the drawbacks of a low base frequency? Noise? Choppy Operation?

Don't know.

Thanks for posting,

Bill

2

General Mach Discussion / Re: Mach3 Output For DC Motor Control

« on: August 04, 2013, 09:43:44 AM »

Hi Tweakie

I think that 50hz base frequency may be unusable, as I understand most systems use 10K or more.

I'm hoping that the base frequency is configurable in Mach3, see below...



I would like to construct a spindle motor speed control driver that will also operate stand alone, so I would'nt have to boot
the computer and launch Mach3, just to drill a hole. Also maybe a foot operated foot switch to reverse the spindle, for tapping threads...

Funny how these projects tend to sometimes expand on their own...

Cheers!

Bill

3

General Mach Discussion / Re: Mach3 Output For DC Motor Control

« on: August 02, 2013, 12:12:58 PM »

Hi Tweakie,

I would be most happy to share my progress ( successes & failures ).

Thanks for Asking.

B.

"All of us together are smarter than any one of us"

4

General Mach Discussion / Re: Mach3 Output For DC Motor Control

« on: August 01, 2013, 11:43:37 AM »

Wow!

You sound angry!

WILL go up in smoke?

You assume I know nothing?

You don't know anything about me.

If it goes up in smoke, I lose a few dollars.

But I have some fun, and I learn something.

I'll modify the circuit and try again, and  I'll solve any problems.

When it works, I'll enjoy the great satisfaction of solving those problems.

Opto isolation protects the computer, fuses protect the motor.

I'm not selling anything here, just learning, and sharing.

Don't take it personally, its not your money.

5

General Mach Discussion / Re: Mach3 Output For DC Motor Control

« on: August 01, 2013, 08:28:41 AM »

Hello All,

I've found that what is needed is what is called a "H-Bridge" circuit.

Simply said, it takes the PWM output from Mach3, and simply amplifies it to the voltage and current required

by the motor.

Has three control pins...

1. Forward
2. Reverse
3. PWM Input

That connect directly to Mach3 output pins on the computer.

The cost of the parts involved for a 200 volt 50 amp amplifier are less than $30.00, ( 4 fet transistors, 4 npn transistors, and an isolator chip if I want to solder my own)

I would rather purchase the thing assembled if the price is right.

I'll let you know what I find out.

Cheers!
B.

6

General Mach Discussion / Re: Mach3 Output For DC Motor Control

« on: July 31, 2013, 11:38:48 AM »

Hello, and thanks for the quick reply!

I understand.

It just did'nt seem efficient to me.

I wonder why someone doesn't sell a board like the one I described?

Seems less complicated.

( Sorry if I sounded like an arrogant know-it-all, I did'nt mean to )

Best Regards,

B.

7

General Mach Discussion / Mach3 Output For DC Motor Control

« on: July 31, 2013, 11:16:53 AM »

Hello Everyone...I'm new here today.

I have a Bridgeport style mill (48" table) with a Leeson 90volt DC motor attached (no speed control other than pulleys)

I plan to convert this mill to CNC shortly, using Mach3 as control software.

I'm well versed in digital and analog electronics, as well as computer science and programming ( basic, C, C++, visual basic )

Sorry, no bragging here, but I don't want anyone to hold back tech info.

My main question is with spindle speed control.

While reading other posts, I notice that with Pusle Width Modulation control of DC motors, most users on this site

convert the PWM output of Mach3 to a 0 - 10 volt analog dc voltage and use it to control a PWM DC motor driver board.

I don't get it. Why not just drive a hefty Mosfet ( like a irf260n (50 amps @ 200 volts) ) directly from the Mach3 output pin? (through a suitable FET driver chip such as  a 4420CN, and  an opto-isolator of course )

Why go from PWM to Analog and back to PWM again to drive the motor?

Am I missing something?

Thanks!