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Author Topic: Speed controller won't hold steady speed - where is the problem?  (Read 9553 times)

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Offline simpson36

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I have two CNC4PC C6 speed controllers. Neither will hold a steady speed. Observing with an analog volt meter confirms the output voltage is fluctuating. I replaced the hook ups with shielded wire, but it didn't help.

Drive is a Minarik MM series which holds dead steady speed using a pot.

I am just curious if anyone is using this controller with success before I spend a lot of time trying to get it to work right if this is just a characteristic of the CNC4PC controller or Mach.
Re: Speed controller won't hold steady speed - where is the problem?
« Reply #1 on: January 12, 2009, 05:19:03 AM »
Hi,

What are you using to power the C6?. Check and see if the power supply to the C6 is fluxuating as well.

If so, there is your problem.


Cheers,

Peter.
----------------------------------------------------
Homann Designs
http://www.homanndesigns.com
email: peter at homanndesigns.com
Re: Speed controller won't hold steady speed - where is the problem?
« Reply #2 on: January 12, 2009, 10:58:03 AM »
I'm not using a C6, but a C11, and I have the same problem.  Often, first thing in the morning, the speed control is completely whacked, and commanding a very slow speed will result in a very high speed, or a wildly fluctuating speed.  After being powered for 10-15 minutes, it finally settles down and starts behaving.  It seems completely unpredictable, as some days it works fine, other days it doesn't.  I had one day that I couldn't get it to behave at all.  I gave up, and went back into the house for the day.  Came out the next morning, and it was working fine.  In every case where I've looked, the supply voltage from the VFD was fine, and the pulsetrain from the SmoothStepper was fine, but the output from the C11 was just whacked.

Regards,
Ray L.
Regards,
Ray L.
Re: Speed controller won't hold steady speed - where is the problem?
« Reply #3 on: January 12, 2009, 11:20:14 AM »
one possibility is the VFD. The VFD produces a lot of  electrical noise, you may need to have a reactor and an EMI filter. all VFD mfg's recommend them. Also check the power supply for the speed controller it should be regulated.
Re: Speed controller won't hold steady speed - where is the problem?
« Reply #4 on: January 12, 2009, 11:25:18 AM »
one more thing, the power to the speed controller must NOT share common ground to keep all things isolated

Offline simpson36

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Re: Speed controller won't hold steady speed - where is the problem?
« Reply #5 on: January 12, 2009, 11:32:08 AM »
Peter: The C6 requires 12v. I am using an old PC power supply for both the 5v for the breakout and the 12 for relays and the C6. The 12V and 5v both read dead steady with the same analog volt meter that clearly showed the fluctuations in the C6 output.

Ray: I have not had any success so far with either of the C6 that I have. I have the same situation as you in that the problem is not consistent, but in my case it is not nearly as severe as you describe, but still not steady enough to be usefull.

I am using the C6 only for the relays and I control the spindle manually using a pot. It would be nice to be able to program increasing spindle speeds as multiple cuts reduce the diameter of a workpiece.

As a newbee, I don't have the experience to now if this is a solvable problem. What I don't like to do is chase my tail for a long while only to find out that the issue I am trying to fix is not fixable, so I was wondering if anyone is using the C6 with success.

Sparkness: I am not using a VFD. It is a PWM drive. The mystery is that the C6 output wavers even if there is no power to the PWM drive, so the problem cannot be RF from the drive . . AND the PWM drive works perfectly using a pot. Additionally, the C6 exibits the same behavior when it is connected to the breakout board with a very short piece of shielded cable and the output is measured doirectly off the output terminals of the C6, so I am perplexed as to where it might be getting interference from.

As a guess, I would put the wavering at about one second peak to peak, but I have not measured it.

TheC6 speed controller uses two voltages. The 5v comes off the breakout (supplied to the breakout by a PC power supply) and the 12v for the follow voltage comes from the same PC power supply directly to the C6. I've checked both and they seem steady on an analog volt meter. In both cases, the power ground is from the same source as the positive voltage. I don't understand what you mean by not sharing a common ground.
Re: Speed controller won't hold steady speed - where is the problem?
« Reply #6 on: January 12, 2009, 12:06:39 PM »
You might want to try the DigiSpeed from Homann Designs.  That's what I plan to do someday when I rebuild my electronics enclosure.

http://homanndesigns.com/store/index.php?main_page=product_info&products_id=39&zenid=7eacd8d7ccf63c46c89881b4949c2234

Peter Homann is a regular here, so if you do have any problems, you'll have no trouble getting it resolved.

Regards,
Ray L.
Regards,
Ray L.
Re: Speed controller won't hold steady speed - where is the problem?
« Reply #7 on: January 12, 2009, 12:29:18 PM »
here is the documentation from cnc4pc explaining how to keep the grounds isolated
http://cnc4pc.com/Tech_Docs/C6R5_WG.pdf
Re: Speed controller won't hold steady speed - where is the problem?
« Reply #8 on: January 12, 2009, 01:25:45 PM »
After a lengthy struggle with a C-11 with no resolution, I went with a PMDX-106 which worked flawlessly from the get-go.
Great support too.....so they say. Didn't NEED any.
RC
Re: Speed controller won't hold steady speed - where is the problem?
« Reply #9 on: January 12, 2009, 01:44:42 PM »
After a lengthy struggle with a C-11 with no resolution, I went with a PMDX-106 which worked flawlessly from the get-go.
Great support too.....so they say. Didn't NEED any.
RC

RC,

I'm in the same boat.  I've had three C11s now, all different revs, and every one has had serious problems I've had to work around by modifying the circuitry.  I'm currently running on one that I had to re-bias the optos to get them to work above a 40kHz step rate with SmoothStepper (At 96K steps/inch, 40kHz doesn't buy you much....).  The speed control has been an on-going problem I just haven't had time to deal with.  Were I to design my own (and I've seriously considered it....) I'd do the speed control in exactly the way Peter Homann did on his DigiSpeed, using a microcontroller, and eliminating the analog circuitry altogether.  I've lost more than a few whole days of work to all the problems.

A friend of mine has a PMDX board, and his has also been flawless.

Regards,
Ray L.
Regards,
Ray L.