SeeMeCNC - Newbie Death Sentence

Dark Alchemist Wrote:
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> Yeah 3.3v vs 5vdc as laptops run the 3.3Vdc and
> most desktops I ever worked on had 5Vdc on the
> IEEE-1284 port.

Are the LEDs for the optos wired to ground or 5V? Even with a 5V port the lines are not guaranteed to go above 2.4V. If the LED is wired to 5V and activated when the port goes to logic 0 it shouldn't matter if it is a 3.3V port.

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[www.hydraraptor.blogspot.com]

it's because of this uncertainty about port voltages, if you look at most of the cnc parallel port breakout boards they almost always have a line driver which knocks the voltage up to 5v,

nophead Wrote:
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> Dark Alchemist Wrote:
> --------------------------------------------------
> -----
> > Yeah 3.3v vs 5vdc as laptops run the 3.3Vdc and
> > most desktops I ever worked on had 5Vdc on the
> > IEEE-1284 port.
>
> Are the LEDs for the optos wired to ground or 5V?
> Even with a 5V port the lines are not guaranteed
> to go above 2.4V. If the LED is wired to 5V and
> activated when the port goes to logic 0 it
> shouldn't matter if it is a 3.3V port.

Yeah, like jolly said because on a laptop the voltage can be 5v but is rarely so you never really know what you are going to get. On a desktop I have never found anything but 5vdc but I haven't touched a modern pc but modern is subjective as they no longer have any parallel port since nothing in the computer world uses that port the manufacturers of the motherboards decided to save a few pennies and eliminated it altogether.

I was surprised recently by an Intel motherboard with a parallel port that did not give enough voltage to drive a solid state relay from logic 1 but it was OK driving to logic 0. It was probably one of the last to have one so I expected it to have symmetrical CMOS drive but it behaved more like TTL.

Fortunately most stand alone stepper drives with opto inputs are active low. Are the Chinese single board 3 axis drives active high?

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[www.hydraraptor.blogspot.com]