5i25 - How to detect machine power state

Hi all,

I'm trying to detect when the CNC Machine is powered-off. The machine's E-STOP pin is 0v when the power is off, it's not floating, but probably not really pulled hard down either.

As a test I tried disabling the 5i25 pull-up resistors (W4=Down), but the gpio input pin sit around 1.5v (even with the machine disconnected). 1.5v register as HIGH, so I installed an external 1k pull-down resistor, which results in 0.8v. This does work, but wondered if anyone had a better solution.

LS

Best way is to use active low output for machine on, for example using a solid state relay (SSR)

PC-5V --> SSR + --> SSR- --> 5I25 OUTPUT

(and set the output to open drain mode)

Thinking about this .. It's probably not ideal to have 5i25 pull-up disabled (floating). The CNC Controller does have 330R pull-ups, but these would only be effective when powered-on.

Maybe I enable the 5i25 pull-up (3.3k), and also put an external 620R pull-down.

Just looking at the voltage divider on the resistors. This should give me:
0.72V with the machine-off
3.36v with the machine-on

** assuming an ideal world, that is that the 5i25 input circuit doesn't have an affect.

Hi PCW,

Sorry I'm confused. Are you referring to ESTOP-OUT or IN?

Sorry, Estop makes me think output

Depending on how hard the machine drives the Estop pin high
you could put a stiffer pulldown, but if its possible an OPTO or transistor
that pulls the 5I25 input low when the machine is on is probably cleaner

i'd be looking at machine-is-on and passing that to a output , rather than estop , estop is final , after that you should not be able to start the machine , untill you have done a full shutdown and restart , where as machine-is-on is switchable i..e f1 f2 etc