Non centroid Tool Length and 3D probes with Allin1DC

[davzing]

I'm trying to do roughly the same. Except I have a two wire probe setup like the attachment. Still doing my research.

[cncsnw]

You will probably have to remove the LED. If it is drawing enough current to light up the LED when tripped, then it is drawing enough current to keep the PLC input "closed".

[centroid467]

I agree. The LED is the main issue with using this probe with ALLIN1DC. I believe some have used it wired so that the LED is reverse biased but that is not recommended because most LEDs are rated for 5V reverse voltage (if they have a reverse rating at all) and you'd be hitting it with 12V. The best option is to remove the LED and use a simple MOSFET inverter circuit like this:

R2 should be anywhere from 1k to 10k. The value itself is not that important but you want to have a reasonable limit to the current through the probe contacts. If Drewtronics gave any specs on that then choose R2 value to put the current within those limits. You'll also want to pay attention to the power rating of the resistor if you go to lower resistance values.

[davzing]

I believe that's exactly it. I was going down the path that I needed an inverting pnp or npn circuit but was getting hung up on having that load. I was going to model it in LtSpice. Didn't think of just cutting it out. Looks easy to just snip the leg on the LED.

[lavrgs]

I have a similar situation; ALLIN1DC and Drewtronics probe. I asked Drewtronics what their suggestion was and was told I could wire the probe backwards - the LED would not work but no harm done.
Would this be an acceptable Centroid solution - rather than snip the LED?
The probe is normally closed is that the base problem?