Messages

431

SmoothStepper USB / Re: SS DISCONNECT SAFETY CONCERNS

« on: December 09, 2008, 06:27:39 PM »

Hi,

Any sort of safety feature is a bonus and should be added if at all possible.

As an example, the ModIO I designed has a charge pump feature. As soon (configurable delay) as  a Modbus master stops sending requests to the ModIO, the ModIO will disable the outputs. 

To me this is just common sense.

I would expect that if you pulled out the USB cable of the Smoothstepper, all the outputs, including the spindle control would be disabled. It probably does this but I haven't checked.

It would also be useful for the Smoothstepper to have a chargepump output similar to the parallel port functionality (maybe it does). It would then retrofit well with breakoutboards that require such a signal.  This chargepump signal would be removed if the SmoothStepper detected that Mach was not communicating with it, or if the SmoothStepper detected a fault with itself.


As an example of poor safety functionality, I was developing a motherboard for the ncPod. While testing the spindle control functionality, I accidentally pulled out the USB cable to the ncPod. The ncPod did not seem to detect the problem and continued to output the spindle PWM signal.  The ncPod has sat on the shelf since that moment.

And in the end make sure you have a proper Emergency Stop circuit as gumbyrulesyou  has stated. It make me shudder every time I see someone write that they have their EStop feeding into Mach3. The purpose of that input is not so that Mach3 can perform an EStop. It is there to politely notify Mach3 that an Estop has occurred and been handled by the appropriate Estop circuitry. After all the EStop buttons are sometimes hid because Mach3 is doing something wrong. In fact ArtSoft should probably replace the EStop input with something more appropriatly labelled, in both the software and manuals.

Cheers,


Peter.

432

Modbus / Re: Allen Bradley micro logix and Modbus

« on: December 09, 2008, 04:00:58 PM »

Peter,

 Yes I see what you mean and i tried It the other way and still no luck


Is there any modbus VB script examples I saw the video in the feed pot  but i may need something more to fall back on

A couple of things to try:

1.  Change the address 40001 to 40005. THis is because plc addressing subrtracts 1 sometimes.
2.  Change the address 40001 to 5. This is because holding registers are in the range 40000 ->


Cheers,


Peter

433

Modbus / Re: Allen Bradley micro logix and Modbus

« on: December 09, 2008, 02:30:49 PM »

Here are some screen shots from Ab software and Mach

The reason why it is failing with Mach is that you are setting up the MAch Modbus test page to read holding registers. From your table of addresses you posted, all the registeres in the 3***** range are input registers NOT holding registers 

In the Modbus  test  page, select input register, rather than holging register. See if it works now.

Cheers,


Peter.

434

Modbus / Re: Allen Bradley micro logix and Modbus

« on: December 08, 2008, 11:26:52 PM »

Looking at your Memorty map definition you can only read the coil space as discretes and not packed into 16 bit registers.

Presumably your PLC allows you to write ladder logic in it. If so, write a ladder to pack the coils into a holding register, then rad the holding register via Modbus.

Cheers,


Peter.

435

Modbus / Re: Allen Bradley micro logix and Modbus

« on: December 08, 2008, 11:15:09 PM »

Hi,

It is not Mach that is giving the error, it is your PLC. Mach is just reporting what is being returned.

I don't know what you mean by "Does the 5 place AB modbus address mapping have any thing to do with it "

Cheers,


Peter.

Don't know why but Mach can't read the input or holding registers or the AB PLC won't let Mach read them  Mach's mod test page gives a( Illegal Data )MSG
Does the 5 place AB modbus address mapping have any thing to do with it


here are the AB address mapping

436

General Mach Discussion / Spindle and Speed control Section

« on: December 08, 2008, 07:42:59 PM »

Hi,

I've noticed that there are quite a lot of questions regarding spindle control, speed set-up, etc. It may be an idea to have a forum section specifically for spindle and speed control related questions.

It would make my life easier as I'm happy to help advise in this area, but, I need to scan a lot of sections to find the relevant postings.

Just a thought.


Cheers,


Peter.

437

Modbus / Re: Allen Bradley micro logix and Modbus

« on: December 08, 2008, 07:34:45 PM »

Hi,

Not sure what your question is. Yes Coils and contacts are single bit ON/OFF discretes.
Holding registers and Input are 16 bit registers.

The Mach3 Modbus setup allows to to read/write to both 16 bit registers and single bit discretes.

Cheers,

Peter.

438

General Mach Discussion / Re: Spindle Speed Troubles

« on: November 10, 2008, 08:14:36 PM »

Pulsewidth setting will significantly affect the response, as will steps/unit, and you have to play with both to get the response you're after, and to get the "S" values scaled as you desire.

Regards,
Ray L.

Hi Ray,

When I way developing the DigiSpeed DC-06,  I designed in circuitry that eliminates the step pulse from affecting the output voltage. The charge pump of the 2907 reacts to the energy in the step pulse, so if the step pulse is fed directly into the chip and the pulse width varies, then so will output. To eliminate this the DC-06 feeds the 2907 with a constant step pulse width regardless of the pulse width sent from Mach3.

When setting the max velocity of the Spindle axis in setup tab, a common problem that many do is provide too many steps, resulting in the maximum output voltage being reached before the maximum RPM setting in Mach is reached. This is then seen as a non-linear response in the actual vs desired speed.

The way to tue a DC-06 correctly is to do the following;

1. Determine the maximum speed of your spindle, for this example assume 10,000rpm.
2. Set your Max pulley speed in Mach to 10,000
3. Set the steps/unit  to 1000 in the spindle axis of the motor tuning tab and set the velocity to its max value allowed
4. run the spindle with the desired rpm set to 10,000. This will run the motor as fast as possible.
5. Adjust the output voltage attenuation potentiometer so that the output voltage is set to the maximum recommended for the VFD or motor controller.
6. leaving the desired speed set to 10,000 go into the motor axis tuning tab and start reducing the max velocity until the motor rpms start to drop.(you will need to in and out of the motor tuning tab to do this.

The point at which the rpms just starts to drop is where the output control voltage is just managing to reach the 10V required to drive the motor at max speed. With this setup you should get a reasonably linear relationship between the desired and actual speed.

Also note that these speed controllers are basically open loop and can be affected by external factors. For example a cold motor/drive-train may have more drag on the system than one that is warmed up, and therefore the speed my read slightly less until it has been running for a while.

I hope this helps,

Cheers,

Peter.

439

General Mach Discussion / Re: Spindle Speed Troubles

« on: November 09, 2008, 10:34:48 PM »

Hi Again jimpinder
I had a good chance this afternoon to do some other tests and try different things. Firstly I took all the power and neutrals to the digispeed from a separate power source, no good. I am in the unique position as well were I am running two BOBs of Se perate Ports. I swapped the digispeed to the other port still to no success. I tried using different pin no.s to no avail.
I think there is something more menacing than a small glitch were I disabled the the spindle in the ports and pins motor outputs config. and the spindle still fires up with the same problem. I am really starting to lean to that the Digispeed board itself is faulty or has some glitch in it. Not sure to replace it with a C6 speed control from CNC4PC or try another Digispeed.
I can get hold of an Oscilloscope (I think if its still there)but I wouldn't have clue how to use it or what I'm looking at.

Hi,

If you can use an oscilloscope, connect it to the step input on the DC-06. Enable the spindle and set a spindle speed so you get a constant smooth step frequency.( At some frequencies the step pulse jitters about a small amount as Mach cannot produce a pulse stream at all frequencies, so adds in extra pulses where needed.)

Then while monitoring the scope, move an axis and see if the step pulse stream changes frequency.

Do the above test with the spindle drive powered up and with it turned off. Let us know what you find.


Cheers,

Peter.




Then

440

General Mach Discussion / Re: pwm mode set up issues

« on: October 04, 2008, 06:37:42 PM »

Hi Dave,

I appreciate your kind reply.

Cheers,

Peter.