Messages

1

General Mach Discussion / Re: Mach3 losing steps

« on: August 09, 2013, 07:08:25 PM »

Hi, did you get any solution on losing steps?

2

General Mach Discussion / Re: PWM spindle - Circuit advice

« on: August 24, 2012, 01:26:14 PM »

You're probably right. Thanks.
It was the only opamp I had left so I gave it a try.
Will order some new and test again.

Thanks for constructive feedback!

3

General Mach Discussion / Re: PWM spindle - Circuit advice

« on: August 23, 2012, 02:41:23 PM »

I've buildt and tested the circuit on enclosed schematics.
Accuracy looks good except at low PWM setting.

My spindle is set to a min. speed of 7200 rpm (VFD setting), but when I set speed to 1000rpm in Mach3 the circuit give 11,5V out! 
(Which make the spindle speed up to max.) 

In normal operation this will not be any trouble, as I never will enter a speed lower than 7200 rpm.

I can live with this, but to be honest I'd prefer to get the circuit working in the lower region as well..

4

General Mach Discussion / Re: PWM spindle - Circuit advice

« on: August 22, 2012, 06:55:37 AM »

Something like this..

5

General Mach Discussion / Re: PWM spindle - Circuit advice

« on: August 22, 2012, 06:27:00 AM »

Thanks John! 

The PWM frequency is set to 1500Hz, I did notice the bad resolution of speed steps, but I was not aware that the PWM frequency was the problem.
I'll try to set PWM to 10Hz and increase the time constant of the rc circuit and to some more recearch.

Yes a voltage follower (opamp) with higher voltage supply should do the trix. Will test and tell

6

General Mach Discussion / Re: PWM spindle - Circuit advice

« on: August 21, 2012, 03:02:36 PM »

Did some testing on my PWM to 0-10V board today.

(Just a small note as I did not mentioned in the last post. I've got no Lynx.
I connect Mach3 directly to my Chinese Huanyang HY01D523b VFD, but I've
been experiencing trouble using the same 'rc' circuit as tread starter.)

Mach base frequency is set to 1500Hz at the moment.

I discovered that you can't fix the problem by raising the circut-voltage.
Check enclosed file. This file show Mach3 speed curve vs VFD speed curve at different working voltages.

10V is optimal for 1:1 scaling between mach speed setting and VFD output, but at 10V you will not get max speed.

Maybe an opamp (rail to rail) as a voltage follower instead of the transistor is the way to go?

Andreas

7

General Mach Discussion / Re: PWM spindle - Circuit advice

« on: August 20, 2012, 03:22:07 PM »

I've got the same problem using the schematic (rc-circuit) shown above.
At mach max speed, output voltage was only 6,5V.

If, i disconnected the pwm to 0-10V circuit to the VFD, then I got approx 9V.
In other words, the VFD has a bit low internal resistance and you'll get a voltage drop.

I added an external powersupply to increase the voltage of the circuit.
This is adjustable, and you can trim output voltage to 10V when mach set to max speed.

I added a small transistor to act as a buffer.
This transistor will counter the voltage drop as per low internal resistance, but will introduce
a static voltage drop of 0,6V, not sure if this is the way to go.

I've buildt this circuit and will test as soon as possible.

Andreas