[ohanasailing]

Hello All..

Making progress on the Thermwood retrofit. Had a quick question regarding the limit switches which are NPN.
As I understand it I am to place a resistor across the positive contact and sensor contact of the sensor and then running ground and sensor back to the KANALOG board. Is this correct? What value should the resistor be? I've attached a pdf of the schematic.

Any help greatly appreciated.

[TomKerekes]

Hi ohanasailing,

That doesn't look right. I don't think a resistor should be needed.

The sensors require +12 and -12 and no GND??

Do you have a specification on those 3 terminal sensors?

Regards

[ohanasailing]

Hey Tom,

Thanks for writing..

I pulled out the 1993 blueprint and looked more closely and sure enough the 'black wire' is tied to -12V and not ground. I called Thermwood for the specs and the "guy that knows everything about the older machines" seemed to be away.. However, they directed me to this part Proximity Home Sensor on their webstore as a replacement which is fairly non-descript. The drawing calls out a Veeder Root VR650800-30. I found this description (INDUCTIVE PROXIMITY 3 WIRE DC M8X1 NO NPN SINK) on another website selling this Veeder Root part.

Knowing this would I tie +12 to brown on the sensor, -12 to black on the sensor and blue back to the opto input on Kanalog along with a DC Ground?

Thanks so much!

[TomKerekes]

Hi ohanasailing,

I don't see any specification for the sensors.

I suppose that wiring would work. +24V would be applied to the sensor. Current would flow from GND into the KFLOP +Opto, then out the -Opto, through the NPN Sinking Sensor to the -12V supply. The Kanalog Opto would "see" 12V and turn on.

Seems like if the sensors can work with 10-30V it would be easier to just use the +12V supply and GND.

Regards

[Acctek CNC]

Normal sersor have three wires , one is Brown is V+ , one is Blue is 0V (COM) .other is Black is signal . V+ connect V+ of 24v supply power , 0V connect COM of 24v supply power , Signal connect the board signal ,

[ohanasailing]

OK Guys...

Nothing felt better than seeing the checkbox toggle on and off on the Digital I/O screen today..

I wound up using +12V (brown) and -12V (black) tied to the sensor and com (blue) and -12V tied to KANALOG Opti in. Worked like a champ.

I feel sort of silly after reading about inductive sensors this morning.. My confusion came from testing the sensors as if they were a switch using a multimeter. It seems that you cannot test an inductive sensor in the same way you would test a switch. My error.

Hopefully I have this correct.. All five homing switches and the over limit switch on the gantry are working correctly with check boxes as they should be! A good day.

Now to get the rest of the controller wired and software utilizing I/O bits correctly. New challenges in the software

Thanks for the help..