[cyclestart]

I have a rotary encoder with it's own 5V power supply, the signals need to be be passed to the control software via LPT. I could do this caveman style by splicing into the LPT cable but that seems crude. Can the main terminal positions 1,2,3,4 be used this way, or put another way, are these positions the same as accessing LPT pins 10,11,12,13 directly ?

Probably a silly question but my grasp of electrical things is weak

[john-100]

Hi cyclestart ,

the four inputs connect to the LPT port via opto isolators

the LED diode inside the optoisolator and a 2K2 resistor is connected to
the G540's internal +12V supply
when a n/o switch grounds the input about 4.5 mA flows through the LED

with an input connected to +5v (TTL logic 1) , the current drops to about
2.2 mA and may still look like a closed switch to ground

you will need to check to see if the encoder has open collector outputs
if not , use something like a 7406 TTL IC to connect the encoder to the G540

John

[cyclestart]

Thank you for taking the time to put together a detailed response, it's appreciated.
Given what you've written I'm going ahead with the modified cable for starters, at least until I'm confident the software is set-up correctly. Then there'll be time to revisit this thread and some new concepts (new to me that is)

The question wasn't so silly after all

[john-100]

Hi cyclestart ,

by testing your setup in stages you will be able to solve any problems
if the encoder and G540 don't play well together

what encoder are you using ?


John

[cyclestart]

A bit of an explanation:

I'm trying to cut a large OD thread with what's on hand.
What's on hand is:
A G540 driven mini-mill
Linuxcnc software to sync the spindle to an axis
A headstock/motor/chuck with encoder which will someday be a lathe. Currently the encoder is an amt102
AMT102 | AMT modular encoders | CUI Inc

The sane thing would be farming the work out but where's the fun in that ?
Using the G540 for this is starting to look a bit like driving a square peg into a round hole.

It looks like there would be no harm in disconnecting pins 10-13 from the G540 ? (ie: splicing into the LPT cable)

[john-100]

Hi cyclestart ,

I've had a look at the AMT102 link
and the output is described as "TTL voltage" squarewave
(open collector would of been ideal )

I expect you will need a circuit to interface the encoder with the G540

you can either use a 74HC06 IC or two NPN rransistors ( eg 2N2222 )
and two resistors (4K7 to 10K ?)

have you built any electronic circuits ?

John

[cyclestart]

have you built any electronic circuits ?

Hello John

I can read a diagram and a multimeter. That's all.
Sorry for the slow replies, playing host to a house guest this week so not much shop time .

[john-100]

Hi cyclestart ,

I've had a quick look for component suppliers in the USA , but must be looking in the wrong places for one IC and not tubes of 25

one possibility is 74LS07 Datasheet
( the 7407 is a non inverting version of the 7406)

for the 2N2222 :-http://www.futurlec.com/Transistors/2N2222.shtml


John