Ohmic Sensor Mistery

[attila0216]

Maybe some pro can help me out with a real mystery i have with Neuron Ohmic sensor. So it is an NPN NO switch basically, works with 12VDC wired to cncdrive HDBB2 breakout board. If i touch the two 2 wires in the air which are workclamp and nozzle wire ohmic "TOUCH " led lights up so it works. BUT and now is the Mystery, if i touch now the two wires into the Plasma pipecutter machinebase lights goes off. What i have also tried, i've wired to a standalone 12VDC power suplly out of CNC so OHMIC total away from machine it works, BUT if i touch it to a ground Rod (and not the CNC table ground rod, doesn't work light goes off!!!

Someone could tell me what the hell is going on. It drives me crazy.


Thank you!!!

[jimcolt]

The Ohmic sensor needs a path that goes back through the Plasma cutters work lead. Essentially the work lead must be connected to the material being cut, and that is where the ohmic contact will sense. Jim Colt Hypertherm

[attila0216]

Yes Jim i know that. I've tried everything. That's why i don't understand why it doesnt work on the machine base and works in the air.

[robertspark]

have you contacted Andrew at Neuron?

neuron.cnc at gmail.com

sounds like you have a mixup between zero volt and ground to me but I know zero about your setup

[tcaudle]

Ohmic sensing knows nothing about "ground" . Its a continuity tester. ( like a meter with the buzzer) it simply measures continutiy between the shield (on side) and the metal (Plate) on the other. The workclamp is tied to the plate. its positive inside the plasma. The shield is floating (unit the torch fires) and so its like an open probe on the meter. Touch it to something tied tot he opposite probe and it "Triggers" Unless the plate is grounded though the table touching you tip side to a ground rod does not close the circuit. If you can short the wires at the sensor and it triggers then its working. Then connect one wire to the clip on the shield and touch the other wire tot he shiled. If that trips then the shield end is working. clip the other wire to the metal with a lead.. now either jog the torch tdown or lift the metal up until ti touches the shield and it should trigger . If it does its all working. The "plate wire " has to ultimately touch the metal plate being cut THOUGH the table frame or tied directly to it. Ground has nothing to do with it

[attila0216]

Thanx but all this i know already what you have wrote here. And yes ground has something to do with because as i sad if i touch the two wires it works, and if i touch this two wires together to ground and any ground not only cnc but another ground rod it's light goes off!!!

So please instead of giving ridiculous comments try to find solution else keep for yourself

[sphurley]

So comments by two of the most respected names in Plasma are ridiculous? Good luck

[tcaudle]

Maybe the title confused me because "mistery" is something whereby a liquid is converted to a mist. Silly me, I though it meant Mystery as in "an unknown"

A person of such immense knowledge and understanding of electronics should be be able to figure out something as simple as using two wires to sense a piece of metal. When we give advice its based on the concept that most of the guys here are not technical experts and need things put forth in a simpler format. Not knowing the exact method Neuron uses for ohmic sensing, I fell back to Physics and basic electricity. If that appears ridiculous then maybe they have a different type of physics in Russia and HE can explain how it works.

[attila0216]

"When we give advice". That is my problem, that you don't give advice just making others look fool. Read you previous post! Did you give any advice? No! Ground has nothing to do with it! So give advice than and explain how that can happen that when i touch it to ground doesn't work anymore. Or do you think i'm just a fool and playing around here!

[sphurley]

Most people asking for help don't go around insulting but here is my best shot.
Open air is infinity for ohms, your plasma machine is less than infinity. You have the sensitivity set too high on the Neuron Ohmic sensor.
Per their web site: Ability to adjusting the ohmic sensor sensitivity

[attila0216]

Sphurley, thank you for advice. I Tried didn't work unfortunatelly. Even Andrew from Neuron doesn't understand how this can happen. Anyway thanx for input.

[BTA Plasma]

You may have a short in your motor. Remove your motor from your rotary and test your ohmic wires for connection. Also do not assume you will get continuity through paint and other parts of the rotary portion.