Hello Guest it is May 24, 2019, 11:38:23 AM

Author Topic: C11G PWM control voltages go down when increasing speed in Mach3  (Read 1826 times)

0 Members and 1 Guest are viewing this topic.

Re: C11G PWM control voltages go down when increasing speed in Mach3
« Reply #10 on: August 26, 2017, 01:29:37 AM »
Hi,
it is certainly possible to use an opamp to invert the signal but it shouldn't be necessary. Finding out what the problem is will probably
stand you in good stead down the road.

If you probe the input to the BoB, that is pin 14 of the DB25 connector. If you flip the board upside down you should be able to probe it without
shorting to any adjacent terminal. Be sure to read up on the pin numbering scheme for a DB25, it is different to most connectors.

I would expect to see a normal PWM, that is to say a short logic high followed by a longer logic low for low rpm. MDI a high rpm, s=20000 say,
and I would expect a long logic high followed by a shorter logic low. Given the description of your problem I think you will find that what you
see will not be what is expected indicating a fault or incorrect setting in the ETH400 which drives the BoB.

I use an ESS and so can't comment on the plugin of any of the CNCDrive products. I would have thought there must be some sort of plugin and settings
that can be made.

One reason I suggested that you disconnect the VFD is so that should the internal impedance of the VFD somehow feed back into the BoB its contribution
can be eliminated. If you experiment and can be 100% sure that there is no conflict between the VFD and the Bob then hook it back up. I don't know
how many times when diagnosing electronic faults I have overlooked or assumed a certain thing only to find later, usually much later, that the fault was in
fact very simple but I precluded myself from finding by virtue of my mindset. I try to eliminate faults like that but realise that as long as my anus points
downwards its not likely to happen!

What are you using for a power supply for the analogue control signal? The BoB itself is 5V so how is it supposed to produce 0-10V? I would have expected the
output buffer to be between 0 and 5V. Here again if the VFD is disconnected it would preclude any confusion as to which device is sourcing voltage.

Craig

My wife left with my best friend...
     and I miss him!

Offline Tweakie.CNC

*
  • *
  •  7,765 7,765
  • Super Kitty
    • View Profile
    • Tweakie.CNC
Re: C11G PWM control voltages go down when increasing speed in Mach3
« Reply #11 on: August 26, 2017, 02:13:09 AM »
Something to check...

The C11G-Rev.8 is intended for the use of Step/Direction signals for spindle speed control.
The C11G-Rev.9 is intended for the use of PWM signals for spindle speed control.

Which version of the C11 BoB are you actually using ?

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: C11G PWM control voltages go down when increasing speed in Mach3
« Reply #12 on: August 26, 2017, 03:41:13 AM »
There is a plugin but I am pretty sure its like the UC100 version where when you open it there is not reallly any parameters to change, but just signaling information.

I believe the board is V9. Literally bought it days ago from CNC4PC so I downloaded the current v9 manual. I will double check the stencil on it to be sure but the layout is exactly the same as the v9 manual. I'll feel pretty stupid if its not v9. Been fighting this speed thing for a few days, ha ha. It does seem to work with the PWM, just inverted in terms of the control, so that makes me pretty confident its v9 - the stencil does say 0-10v for sure on the one pin I just cannot say for sure it says v9. Easy to check when it is in front of me


It has a 12v input that powers the PWM 0-10v and I have a dedicated 12v switching supply.

I emailed CNCDrive tech support a 2nd time with both a question about the IEEE 1284 jumper and about the inverted speed control.  They are pretty good about replying but not sure if they will on a weekend.

I will report back with some more answers and waveforms assuming I can figure out how to use my scope (ha ha).  I've only ever turned it on a few times.. bought it with the intent of learning to use it some day. I have an electronics genius friend that could probably help me if he can spare time.

Thanks again both of you. Cool that I am getting replies Friday night (I am in LA time zone wise)
« Last Edit: August 26, 2017, 03:44:05 AM by Lindzr »
Re: C11G PWM control voltages go down when increasing speed in Mach3
« Reply #13 on: August 26, 2017, 05:09:12 PM »
The board is v9.

Do you think I could simply reverse the spindle parameters for higher analog frequency and lower analog frequency from 120hz low and 400 hz high to 400hz low and 120hz high?
Re: C11G PWM control voltages go down when increasing speed in Mach3
« Reply #14 on: August 26, 2017, 05:27:39 PM »
Hi,
I don't think so, my VFD is made by Delta and so will not be identical however all VFDs have similar features. One instruction provided is that
min frequency must be numerically smaller than max frequency.

Craig

My wife left with my best friend...
     and I miss him!