Messages

2851

Mach4 General Discussion / Re: Where is Mach4 Plasma screen set?

« on: March 21, 2019, 10:40:32 PM »

Hi,
really THC is a realtime operation and as such must be done by the controller not Mach.

Until very recently the only external motion controller that has THC support is the Hicon by Vital Systems.
Warp9 is days away from releasing its THC support for the SmoothStepper. We have been waiting a long time for it.
All reports, so far, from the testing suggest that its going to be good, and Warp9 doesn't charge extra for it unlike
Vital Systems.

NFS have decided to get in on the act as well. They have written a THC screen and programmed THC support in Lua.
You must recognize however that a programmed THC routine is fairly slow due to communication delays. If the
Z axis correction speed required of your machine is not high then NFS's solution will work. If however you require genuinely
fast THC support then you will need realtime support, the Hicon is ready now and the ESS is coming very soon.

NFS has not released THC support officially yet but is available as the latest development version on the ftp site.

Craig

2852

Mach4 General Discussion / Re: Is there a Gcode command to reference all axis home?

« on: March 21, 2019, 10:29:48 PM »

Hi,
no, there is no Gcode that does that.

There is however a Mach function that does it:

LUA Syntax:
rc = mc.mcAxisHomeAll(
   number mInst)

Description:
Used to start an axis homing.

Parameters: Parameter Description
mInst The controller instance.


Returns: Return Code Description
MERROR_NOERROR No Error.
MERROR_INVALID_INSTANCE The mInst parameter was out of range.
MERROR_NOT_NOW The operation could not be completed at this time.

Thus you could use the API in a macro.

Or you could call the RefAllHome() function (in the screen load script)

Code: [Select]

-- Ref All Home() function.
---------------------------------------------------------------
function RefAllHome()
    mc.mcAxisDerefAll(inst)  --Just to turn off all ref leds
    mc.mcAxisHomeAll(inst)
    coroutine.yield() --yield coroutine so we can do the following after motion stops
    ----See ref all home button and plc script for coroutine.create and coroutine.resume
    wx.wxMessageBox('Referencing is complete')
end

Craig

2853

Mach4 General Discussion / Re: input signals

« on: March 21, 2019, 02:40:47 PM »

Hi,
you need to give some thought as to when this code executes, and if it executes repeatedly every few milliseconds or
so, what prevents the movement code executing multiple times.

As it is written it looks like this ode should go in the PLC script. So you are polling the input, it works
but is inefficient.

So lets assume the signal changes state, ie the conditional MatHmLimit==1 then the movement codes execute.
Because you have not used GcodeExecuteWait() the movement codes return immediately. This could mean that
BEFORE your machine has had the time to move off the home switch the PLC script will run again the conditional
is still true so a second lot of movement codes is executed. Is that what you want?

The second issue is that you are attempting to execute Gcode, that is your motion codes, yet you have not tested to
see whether Mach is in the idle state and can accept motion codes.

I suspect that what you are hoping that will happen is that this will happen when you hit <RefAllHome>. You will
be dissapointed because when RefAllHome is running, being in the screen chunk Mach will never be in idle state
and therefore your motion  codes can't run.

Please explain what you are trying to achieve and when you are trying to achieve it.

Craig

2854

Mach4 General Discussion / Re: input signals

« on: March 21, 2019, 02:04:02 PM »

Hi,
where are you going to put this code, the PLC script, a macro?

Craig

2855

General Mach Discussion / Re: Do you use a Charge Pump?

« on: March 21, 2019, 02:37:58 AM »

Hi Tweakie,
ditto.

Craig

2856

General Mach Discussion / Re: Have you ever blown up a PC?

« on: March 21, 2019, 02:36:25 AM »

Hi Tweakie,
when I used parallel ports I had the same arrangement as you and never had any problems either.
I now use an ESS, and I suppose it is just as possible for a 'bad' input to damage the ESS, and yet it
hasn't happen either.

Craig

2857

General Mach Discussion / Have you ever blown up a PC?

« on: March 21, 2019, 02:02:40 AM »

Hi All,
trying to get a feeling for the number of people who may have damaged a PC because they chose not use
opto-isolated inputs.

Thanks for taking the time to respond.

Craig

2858

General Mach Discussion / Do you use a Charge Pump?

« on: March 21, 2019, 01:56:48 AM »

Hi All,
just trying to get a feel for the numbers of people who use a charge pump to 'safe' their machine.

Thanks for taking the time to respond.

Craig

2859

General Mach Discussion / Re: My home build machine

« on: March 21, 2019, 01:42:56 AM »

Hi Lumber60.
'plans are overrated'.....'I never bother drawing plans until I've finished building it'.

Craig

2860

General Mach Discussion / Re: Mach3 / PMDX-122 Issue

« on: March 21, 2019, 01:34:17 AM »

Hi,
we should do some polling.

now has a Charge Pump - it is for added SAFETY to prevent machinery motors from moving UNTIL operator using MACH3/4 is FULLY in control.

I am well aware of what a charge pump is and what it does and guess that most understand it also. I have never used a charge
pump with either Mach3 and parallel port or Mach4 and ESS, without problems. This comes in large part as a deliberate
design choices on my part that all potentially dangerous (when uncontrolled) motors and pumps are naturally in the OFF
state should the controller be out of service.

My guess is that 3/4 of all Mach users do not use a charge pump. Once upon a time yes is was the norm....not so today.
Would be worth doing some polling.

PMDX-105 optional card is to provide Opto-isolation so that limit/home switches can optionally operate on higher voltages (e.g. 12V or 24V) instead of just TTL level of 5V.

I certainly agree that optos allow an increase in flexibility, being able to use 24V devices is worthy of consideration.

Advantage of higher voltage limit/home switch is that HF noise from VFD & steppers for example will be less likely to falsely trigger the limit switches. HF noise or spikes will have to swing higher voltages to falsely trigger limit switches running at 12V or 24V  instead of 5V.

This is a widely held opinion but it is too simplistic to be accurate. The real determinant of noise immunity is not voltage
but impedance.

A 24V device may have a very high input impedance and therefore any inductive spike causes a substantial voltage swing
and potential interference with the signal of interest. The same circuit but at lower impedance with the same inductive spike
will have a proportionately lower voltage swing, ie less interference.

Thermal noise is described by Boltzmans equation:
P=4.k.B.T.R
P=noise power
k=Boltzmans constant
B=bandwidth
T=temperature (⁰K)
R=resistance (or impedance if reactive)

So for a given temperature and bandwidth, the lower the resistance, the smaller the noise power.

Have you wondered why so many electronic communication systems run at such low voltages? Take Ethernet for
instance, a voltage swing of less than 1V between a '1' and a '0'. That you might have thought that would render Ethernet
susceptible to noise yet in fact Ethernet is very noise resistant. The reason is the low impedance that Ethernet operates
at.

It is possible therefore to have a 5V TTL signal be as noise immune as a 24V signal IF the impedance is chose wisely.
For instance I do not like to load a 74LS TTL output more than about 10 mA, despite the maximum rating being 24mA.
By the same token I always like to load a TTL circuit such that an ON state current of at least 10mA, ie low to moderate
impedance for the sake of noise immunity.

Another advantage of Opto-isolation is to prevent PC motherboard or parallel ports BLOWING UP

Ok, yes you can blow up a PC by backfeeding the parallel port.......but when was the last time you heard of anyone
actually doing it? There again I think we should do some polling to find out. I know lots of people run scared but
I don't know anyone who has actually blown up a PC.

Hey, I usually have a good go at getting electronic stuff to go......but I have an AWSOME reputation for blowing stuff
up.....and I haven't managed to do so yet and I've got non isolated inputs and have done for five years.

Craig