Messages

301

General Mach Discussion / Re: CNC4PC C11G Analog Output Spindle Control

« on: January 05, 2010, 01:55:49 AM »

Personally, I'd take a PWM spindle control interface over a Step/Dir charge pump any day.  Peter Homanns DC03 works flawlessly, and is VERY accurate and linear.  I can typically set VFD frequency to with 0.5Hz or better.

Regards,
Ray L.

Me too.

302

General Mach Discussion / Re: CNC4PC C11G Analog Output Spindle Control

« on: January 04, 2010, 09:23:13 PM »

One other thing I cannot figure out is the pulse width setting, can you not change the value independently?  I had to set it to 10us on the spindle to get the voltage high enough, but I would like to have the servo pulses be 5us.  Is there any way to do that?  Now it just changes all the values at the same time.

Dustin

The problem you have is that, the speed controller chip converts the pulses from the step pulse to an analog voltage via a charge pump. With a longer step pulse, more energy is put into the chargepump and a higher voltage results.

On by Step/Dir DigiSpeed, I have additional circuitry that ensures that the pulse length fed to the chargepump, is allways the same regardless of the Mach3 step pulse width. That way, you can set the step pulse width to match what your motor drives need rather that what the analog output voltage signal needs.

http://homanndesigns.com/store/index.php?main_page=product_info&cPath=1&products_id=39


Cheers,

Peter.

303

General Mach Discussion / Re: Gecko G540 Based Stepper Controller Kit Wiring Diagram

« on: January 03, 2010, 12:42:28 AM »

Hi ,

Just a quick note to let you know that version 5 of the schematic is now online. It now includes the freewheel diodes for the relays, a star connected earth and a few other improvements.

The schematic can be found towards the bottom of the following page.

http://homanndesigns.com/store/index.php?main_page=product_info&cPath=27&products_id=90

Cheers,

Peter.

304

General Mach Discussion / Re: PWM Questions

« on: December 31, 2009, 07:10:48 PM »

I'm trying to figure out some specifics about the PWM output.  No luck on the forum, so maybe this could be a reference for others.

Questions:

1.  Is there a set pulse rate for the PWM?  If so, what is it?  Or, does it change if you change the Kernel Speed?

2.  If I set Pulley #1 to 0-100, does that mean that I can vary the PWM by using S0 - S100 in a G-Code line?

3.  If I set the PWM Base Frequency at 500, that is a divisor into the the Kernel Speed.  So, if Kernel Speed is 25000, the I have 25000 / 500 = 50 possible speeds.  What are the ins / outs of setting the Frequency higher or lower.  That is, if I set this at 10 do I get smoother output?  Why would I set this higher or lower?


My guesses at the moment are:  1.  No clue  2. Sounds right but I don't think it actually works that way  3.  I think too small will make it jumpy

1. The base frequency and the kernel speed determine the resolution of the PWM output. The resolution is the number of PWM steps you have between 0 rpm and your maximum speed.

The resolution is determined by kernel Speed/PWM base frequency. So;

For Kernel speed of say 25KHz and a PWM base frequency of say 10Hz you end up with,

25000/10 = 2500 steps. If you have a PWM base frequency of say 100Hz then you get;
25000/100 = 250 steps.

If you have a spindle maximum speed of say 10,000rpm, then the resolution will be
4 rpm per step for the 1st example, 10000/2500 = 4. for the 2nd it will be 40rpm per step.
10000/250 = 40.

The higher you set the PWM frequency, the lower the resolution you can achieve. That said, an open loop speed control would be hard pressed to use a resolution of 4 rpm.

From a practical point of view I recommend a base frequency of 50hz. I provides good response and seems to be less affected by electrical noise.

2. The PWM output is a mark/space waveform calculated as a % of the maximum spindle speed. So if you set the max pulley speed to 1000, then the PWM output ratio is calculated as;  PWM = Speed/Max Pulley Speed  * 100. So if you set speed to 300rpm by S300  the PWM ratio will be
300/1000 *100 = 30%

3. I have found that a higher base PWM frequency, gives better noise protection.
    If you have a low base frequency, you need more filtering to keep the output ripple down.
   


Cheers,


Peter.

305

General Mach Discussion / Re: Gecko G540 Based Stepper Controller Wiring Diagram

« on: December 26, 2009, 08:33:22 AM »

Hi,

I've updated the schematic to V3. It now is split into 2 pages. The first contains what is in the Controller. The 2nd contains external bits and pieces.

I've added a cooling fan (Gecko Chiller) to the diagram as well.

The schematic is still in the same spot at;

http://homanndesigns.com/store/index.php?main_page=product_info&cPath=27&products_id=90

Tomorrow I'm off for the Annual family camping trip at Port Fairy for 2 weeks. It's on the Western Coast of Victoria.


Cheers,


Peter.

306

SmoothStepper USB / Re: SS and spindle motor control

« on: December 25, 2009, 05:00:32 PM »

Hi Hunserv,

For the parallel port, the resolution of the PWM is the Mach3 kernel speed/PWM base frequency

So, if you have a Mach3 kernel frequency of 45KHz and a PWM base frequency of say 10Hz, then the resoulution  of the PWM output is 45,000/10 = 4,500 steps between 0% and 100% of maximum speed. So that is 0.022%

Therefore if you have a maximum spindle speed of 10,000rpm, the speed resolution you can get is 10,000 / 4500= 2.22 rpm

For the smoothstepper, I'm not completely sure but I think that the equivalent value for the kernel speed is 4MHz so the resolution is a lot higher.

Cheers,


Peter.

307

General Mach Discussion / Re: Gecko G540 Based Stepper Controller Wiring Diagram

« on: December 23, 2009, 04:15:35 PM »

Hi Dave,

I revised the diagram and added an IEC connector to one of the relay outputs, so you may want to download the Rev2

Cheers,

Peter.

308

General Mach Discussion / Re: Gecko G540 Based Stepper Controller Wiring Diagram

« on: December 23, 2009, 12:59:25 AM »

Hi Dave,

In my diagram I show 2 relays hooked up to the G540. Your relay would be hooked up as a replacement to one of those.

You need to check the coil voltage of the relay you have. The ones in my diagram are 48V coil relays so one end of the coil goes to the 48V power supply the other end to one of the 2 outputs of the G540, either pin 5 or 6.

If your relay coil has a different voltage rating then you will need an additional supply. Look at the Gecgodrive manual for the G540. It shows a diagram showing this.

You then need to use the relay contacts  to switch the power active line to your router to switch it on and off.

Does this all make sense or do you need more clarification?

Cheers,


Peter.

309

General Mach Discussion / Re: Converting Sherline Linux/EMC to Windows/Mach3

« on: December 22, 2009, 06:46:42 PM »

Dave,

Have a look at the Mach3 manual under the configuration settings.

Basically, you can set which parallel port pins are used to drive which axes. You could change the configuration of these pins so that you don't have to swap the cables around.

Also you need to set up the step/inch for each axis. It sounds like it is wrong for the Y-Axis.

The sherline controller is a 1/2 step controller from memory. So, with a 200 steps/rev motor and a 1/2 step controller, and a 20 turns/inch leadscrew, you should have the steps/inch set to;

200 x 2 x 20 = 8000 step/inch


Cheers,


Peter.

310

General Mach Discussion / Re: Gecko G540 Based Stepper Controller Wiring Diagram

« on: December 22, 2009, 07:39:30 AM »

Hi RC,

Yes, that is correct.

Thanks,


Peter.