[Help] Capacitive sensor acting weird

Hi!

I've been printing for some months now. Without auto bed levelling and it's a pain in the ass.
I already had the sensor ljc18a3-h-z/bx so I printed a mounting and have been trying to get it to work for the last three hours.

I've read this topic. [forums.reprap.org]
I've tried this configuration [forums.reprap.org]
What happenes is that the LED is ALWAYS on and from the host I get OPEN all the time.

I tried this although mine is NPN [forums.reprap.org]

Still always OPEN!

Can someone clarify please!

Probably in your config.h; z min endstop triggered = false/true, do check this part

It's a normally open sensor so the led should only come on when it is placed next to a surface. Test the sensor first connect negative and +12v leave the signal wire unconnected. The led should be off. Bring the sensor near a surface usually around 2-4mm away the led should come on.

If you now put a multimeter from negative to the signal wire you should be reading 0v when nothing is nearby and +12v when something comes near the sensor. If this isn't working and you have no wiring errors the sensor is faulty.

Wire it to your printer as follows. Connect +12v to your PSU, connect negative to PSU, run the signal wire through a 5v voltage regulator (which needs a ground/0v connection also) and then to your printers z min endstop. Which is the pin nearest the outside of the ramps board.

The marlin configuration might need a bit of messing about with there are two settings endstop logic and pull up resistors. Just try all 4 combinations until you get open when the carriage is away from the bed, and closed when it is close to the bed.

If the LED is always on, then the sensor has failed.

These capacitive sensors seem to fail regularly... I've gone through two so far, and now prefer manual height setting.

Quote
frankvdh
If the LED is always on, then the sensor has failed.

These capacitive sensors seem to fail regularly... I've gone through two so far, and now prefer manual height setting.

I think I will take your word for it.. Yet just to add,

I've struggled with it and got it work using the voltage divider. Then realized that it's not sensing the glass but rather the heatbed beneath. So I glued Aluminum Foil beneath the glass bed. Still the results are very inconsistent.
I've to play around with the sensitiviy dial on top a bunch of times while calibrating. Should I just replace the sensor?

Another thing I remembered now that I plugged the sensor where the extrder fan goes once. In the WMP thing can happen. Can this damage it ?

Quote
DjDemonD
It's a normally open sensor so the led should only come on when it is placed next to a surface. Test the sensor first connect negative and +12v leave the signal wire unconnected. The led should be off. Bring the sensor near a surface usually around 2-4mm away the led should come on.

If you now put a multimeter from negative to the signal wire you should be reading 0v when nothing is nearby and +12v when something comes near the sensor. If this isn't working and you have no wiring errors the sensor is faulty.

Wire it to your printer as follows. Connect +12v to your PSU, connect negative to PSU, run the signal wire through a 5v voltage regulator (which needs a ground/0v connection also) and then to your printers z min endstop. Which is the pin nearest the outside of the ramps board.

The marlin configuration might need a bit of messing about with there are two settings endstop logic and pull up resistors. Just try all 4 combinations until you get open when the carriage is away from the bed, and closed when it is close to the bed.

'

I did that budd. Yet still always LED on lightly and bright only when close to an object.
Also the accuracy is terrible!

Quote
ishe7ata
I've struggled with it and got it work using the voltage divider. Then realized that it's not sensing the glass but rather the heatbed beneath. So I glued Aluminum Foil beneath the glass bed. Still the results are very inconsistent.
I've to play around with the sensitiviy dial on top a bunch of times while calibrating. Should I just replace the sensor?

Capacitive sensors are sensitive to temperature and moisture. They are OK for sensing that something is close (which is what they are designed to do), but they are not intended to measure precise distances in an uncontrolled environment. So I recommend using other types of sensor. After experimenting with several technologies, I developed an IR sensor for use on glass, see [miscsolutions.wordpress.com].

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].