Hello Guest it is May 08, 2021, 01:18:44 AM

Author Topic: LPT port "active low", "active high"???  (Read 7042 times)

0 Members and 1 Guest are viewing this topic.

LPT port "active low", "active high"???
« on: February 23, 2014, 05:13:58 PM »
Hi guys,

Im completely new to Mach3 and when I want to set up my Mach3 to my THC I have to set up the ports and pins below:

Inputs

-      Pin 10 – estop – active low
-      Pin 15 – THC On (same as ArcOK) – active low
-      Pin 12 – THC Up – active low
-      Pin 11 – THC Down – active low

Outputs

-      Pin 1 – Output #1 – (Torch On) – active high
-      Pin 17 – Charge pump  

I would like to ask that what is the different between active low or active high in terms of measured voltage on LPT port pins?
Should I measure higher voltage where I set up "active high"? Or what is the meaning of it? Why is it referred as "active"?

Furthermore I was also told that pin 17 "Charge pump" is a safety setting which prevents my plasma cutter to start automatically by windows issue. Does it mean that if I set this setting up (pin 17 Charge Pump) in Match I should only get 5V on pin 17 if I lunched Mach3 software? Or I have to start Mach3 software and after I still have something to do to get 5V on pin 17? Sorry for dumb questions but I just want to make sure of the proper operation.



Many thanks

Offline Fastest1

*
  •  920 920
  • Houston, TX
    • View Profile
LPT port "active low", "active high"???
« Reply #1 on: February 25, 2014, 07:32:12 AM »
The questions aren't dumb.

High (5v) low (0v). Active "high" is really "active low"'unchecked. You will measure a higher voltage (anything above 3-4volts) or close to 0 if low. These numbers aren't exact and it is really just an on or off signal. Setting up some forms of switches will require using resistors til you get these voltages close. Don't know why they call it active? Maybe because it will change status instead of being static?

Regarding the charge pump, it is a safety device. The controller is looking for the presence of a signal. Until this signal is seen no motion control will take place. IIRC it is a 25Khz signal not a voltage but I could be wrong there.

  Your equipment is pretty forgiving in relation to "active low" being checked or not. If it doesn't work one way, try checking or unchecking active low. No harm will be done if it is wrong. It won't work but no damage is done.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline stirling

*
  • *
  •  2,188 2,188
  • UK
    • View Profile
    • www.razordance.co.uk
Re: LPT port "active low", "active high"???
« Reply #2 on: February 25, 2014, 01:01:06 PM »
ACTIVE just means exactly that i.e. what voltage (high or low) ACTIVATES whatever function is attached to that pin. You shouldn't think of HIGH as ON or LOW as OFF.

Charge pump puts out a 12.5KHz signal on an output pin i.e. the VOLTAGE on the pin changes from high to low at that frequency. It is only present when Mach is running and out of reset. You can configure it (like any other output) to be on any output pin you like - not just pin 17
 
Re: LPT port "active low", "active high"???
« Reply #3 on: February 25, 2014, 04:29:13 PM »
Thanks you guys. I really appreciate your answers. So if I understood you well when we want send a "turn on" signal onto pin 10 ( eg. Estop which was set in Mach as "Active Low") then we should send around 1V and thats it?! If we want to turn it off then we just open that circuit on pin 10 and we dont send any voltage. Am I I correct?
We just want to create some sort of estop button and we are just planning to create a circuit.
Thanks again!

Offline stirling

*
  • *
  •  2,188 2,188
  • UK
    • View Profile
    • www.razordance.co.uk
Re: LPT port "active low", "active high"???
« Reply #4 on: February 27, 2014, 04:26:56 AM »
E-Stop signal to Mach

Many ways to skin this puppy - but two are:

input pin ----------- NC switch --------------- ground (set pin Active HIGH)

or

input pin ----------- NO switch --------------- ground (set pin Active LOW)

The first is generally preferred.