Re: LM324N op amp and toolchanger sensors

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "caudlet" <thom@t...> wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Lance Hopper"
> <snaggletto@c...> wrote:
> > Hello,
> > On an existing lathe and sensor circuit board I have 4x,

forked,

> > optical sensors and an LM324N op amp. This circuit is used to
> sense
> > the position of my tool turret. There are 6 output wires, 2 are
> > power wires, and the other 4 are for each sensor.
> >
> > On my PMDX 120 breakout board, wiring to the inputs requires

two

> > wires, one into the input and the other into the common return.
> With
> > the optical sensors and LM324N, I will only have one wire for

each

> > sensor, no common return. How can I wire this to my PMDX 120
> > breakout board to get the sensor input without a common return

wire

> > to complete the circuit?
> >
> > Is it possible that the - supply wire going into the sensor
> > circuit board could be used as the common return for all 4

sensors??

> >
> > Any help would be appreciated.
>
> Most likely the LM324 (single supply op amp) is used as a Schmidt
> trigger (cleans up the signals from the opto's). Since an LM324
> references everything to Gnd the signals will swing from gnd to the
> supply voltage. If the PMDX card has an isolated ground on the
> inputs you will either have to tie it to the supply ground (and

loose

> any isolation) or run the opto card from an auxillary supply with
> it's ground referenced to the PMDX input ground. I was under the
> impression that the PMDX card does not have an isolated input so

you

> should be able to just interface the 4 outputs back using the power
> supply ground provided it is a 5V supply. IF the card runs on 12 V
> then you you have a problem. You can't pump 12V directly back to

the

> parallel port. You will have to build an interface circuit. You

can

> use 4 NPN small transistors and run the collector supply from +5 or
> use an open collector buffer IC to do the level translation.
>
> The inputs on a Campbell card are opto isolated and you can use

them

> with 12V (or even 24) devices for postion sensing.

Here is info on the PMDX 120 board;

http://www.pmdx.com/PMDX-120/PMDX-120_Manual_12.pdf

page 7 "contact closure inputs"

"The return pins are common to all 5 inputs but isolated from PMDX
ground."

"Inputs are opto-isolated and accept contact closure switches or open-
collector sensor outputs."

"Over-voltage protection tolerates direct application of 110VAC to
switch inputs without damage to your computer or the PMDX-120 board."

"The PMDX 120 supplies approximately 12V with an open circuit, and
will source up to 20mA max to each contact closure pin when connected
to the common return."

Does this information change what you said above? I think you can
tell me what I need to know, you just need to know what I'm working
with.

I've not yet figured out what supply voltage is needed for the
circuit (LM324 and 4 opto's).