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Author Topic: ative low or active high??  (Read 4138 times)

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ative low or active high??
« on: April 08, 2015, 01:17:49 PM »
having now (after many months) a basic understanding of gcode,Mach3, Ports and pins etc and my machine
sort of running ok i decided to start again at page 1 of the manual and go through it step by step for about the
umpteenth time!!

This is the first of a few questions concerning some thing needing  explaining
Quite a few guys have been helping and each with his own suggestions resulting in
some unknown differences being made to the setup and settings.
 
Machine setup Page 4.7 says i must tick the active low button on in ports and pins  but i see my
setup has active low off ?? is this a serious issue?
What difference does it make?? anything i could detect when using the machine

all comments gratefully acknowledged

fred evans
think of the trees-- use both sides of the computer paper

Offline DMBGO

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Re: ative low or active high??
« Reply #1 on: April 08, 2015, 03:54:53 PM »
Low is "off" or connected to common or ground, whereas high is on. Therefore a high signal would be at say 5v or in some cases 24v. For Mach3 it is usually 5v when high, and 0v when low.
That being the case, the tick box next to the signals, asks you to define whether the signal is "active" when it is high or when it is low.
Therefore, if you were to change a signal in ports and pins to "active low" from "active high" it would cease to function as intended since it would be off when the software was expecting it to be on, or vice versa.
So to answer your question, yes you would detect that something was no longer working when using the machine
Regards
David
Cheers

David
Re: ative low or active high??
« Reply #2 on: April 09, 2015, 03:54:15 AM »
Thanks David-- the machine is functioning OK so looks like I was worrying about nothing
I am at work at the moment and will check up tonight to see if I have perhaps
misinterpreted the tick or the cross-.
many thanks
think of the trees-- use both sides of the computer paper

Offline stirling

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Re: ative low or active high??
« Reply #3 on: April 09, 2015, 04:12:45 AM »
LOW does NOT mean OFF and HIGH does NOT mean ON.

Low can be used to mean ON or OFF and High can be used to mean ON or OFF. That's exactly why the term ACTIVE(high or low) is used. If a system is set ACTIVE HIGH then it means just that, ACTIVE when HIGH. If on the other hand a system is set ACTIVE LOW then it means just that, ACTIVE when LOW. i.e. we use the term ACTIVE rather than ON because it's more meaningful and also helps to avoid the mistake of thinking HIGH is synonymous with ON and LOW is synonymous with OFF.

What change will you see if you were to change the active setting of something? It depends entirely on what that something is. If for example it's a direction pin then all that will happen is your axis will go the opposite way it did before. If on the other hand it's a spindle relay pin then it will be off when it should be on and vice versa. If however it's a step pin then it MAY make no difference whatsoever or it MAY stop your system from working properly.

i.e. Some active settings are down to you and how you've designed your system and changing them should have obvious and predictable results, a spindle relay for example. Others though should be set according to your hardware data sheets - a step pin for example.

Offline DMBGO

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Re: ative low or active high??
« Reply #4 on: April 09, 2015, 04:24:18 AM »
I'm sorry, but I disagree. High is higher than low, either can be used as an active signal. It would be very confusing to have a high signal that is say 30v and a low signal that is 300v. I realise it is academic, but there you go. I think mr google would confirm my description, but in a far more lucid manner.
Cheers

David

Offline stirling

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Re: ative low or active high??
« Reply #5 on: April 09, 2015, 05:28:41 AM »
I'm sorry, but I disagree.
Sorry David - I'm not clear exactly what you're disagreeing with.

High is higher than low

Can't argue with that. Exactly where did I suggest otherwise?

either can be used as an active signal.

Exactly what I said.

It would be very confusing to have a high signal that is say 30v and a low signal that is 300v.

I absolutely agree, exactly where did I suggest otherwise?

I stand by everything that I ACTUALLY said.

Offline DMBGO

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Re: ative low or active high??
« Reply #6 on: April 09, 2015, 06:36:30 PM »
I must have been having a bad hair day. Bloody hormones!
Sorry
Dave
Cheers

David

Offline stirling

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Re: ative low or active high??
« Reply #7 on: April 10, 2015, 04:53:22 AM »
I must have been having a bad hair day. Bloody hormones!
Sorry
Dave

 ;D ;D ;D

Anyway - back to Fred... (you still with us there Fred?)

Machine setup Page 4.7 says i must tick the active low button on in ports and pins  but i see my
setup has active low off ?? is this a serious issue?
What difference does it make?? anything i could detect when using the machine

Page 4.7 of what Fred?

You'd have to say which pin/function you're talking about to be able to answer this with any meaning.
Re: ative low or active high??
« Reply #8 on: April 10, 2015, 06:35:13 AM »
Hello There
Page 4.7 of the mach3 turn manual-- sorry will be more precise next time
I will find the detail of the pin no tonight when I get home and put that in

regards

fred
think of the trees-- use both sides of the computer paper
Re: ative low or active high??
« Reply #9 on: April 10, 2015, 10:24:36 AM »
OK Stirling now i got it
the reference is in section 4.6.3 and refers to the general settingh up of stepper motors.
the reference is as follows  (typo's excluded)
"Stepper drive electronics usually use Active  Lo configuration mach3 should be set up so these outputs are acrtive lo
..... " it goes on to say that inverted setting up will resuly in very rough and unreliable running
think of the trees-- use both sides of the computer paper