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Auto Bed Leveling with an Inductive Proximity Sensor

Posted by quillford 
Auto Bed Leveling with an Inductive Proximity Sensor
October 18, 2014 05:24PM
I have tried the following three inductive sensor on RAMPS 1.4, and none of them worked (1 2 3). I also tried the one on my Printrbot which worked. Two of the three sensors I tried are the same model number as the Printrbot probe. The problem I am having is that the probes will not change state even though the LED on the probe itself changes correctly. Is there something I need to do to the probes to make them work? Did I simply receive three defective probes?
VDX
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 18, 2014 07:26PM
... several questions: - have you measured the output? - did it change with the LED or not? - which driving voltage (6-36V!) and how did you connect it to the 5V input?


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org]
Call for the project "garbage-free seas" - [reprap.org]
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 18, 2014 07:28PM
Quote
VDX
... several questions: - have you measured the output? - did it change with the LED or not? - which driving voltage (6-36V!) and how did you connect it to the 5V input?
I have not measured the output. It did not change with the LED. I connected it to the endstop positive and ground pins.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 18, 2014 09:55PM
1 is normally close while 2 and 3 are normally open. Most likely for 2 and 3 you need to change the logic in marlin. Also my advise wire the sensors to your power supply instead of ramps and put an LM7805 from signal of the sensor to your ramps signal pin.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 18, 2014 09:58PM
Also, you have two types NPN and PNP, need the check which one is the correct for ramps
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 18, 2014 11:43PM
Quote
ggherbaz
Also, you have two types NPN and PNP, need the check which one is the correct for ramps
I have tried both. Neither of them work.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 19, 2014 12:07PM
Using sensor 1 that is the correct type, connect brown to + blue to - and black to signal. Do M119 if shows triggered switch logic, do M119 and verify that is open, put a metal close to it and do M119 again should say triggered, if not, then you will have to used 12 volts and a voltage divider or LM7805 for signal to ramps.
Now this might be an stupid question: what kind of heated bed you have? Do you have enough metal there for the sensor to work properly?. I used capacitive sensors instead because they read any material and they read the top and not bottom of bed (glass), yes you need to have a table of offsets for different bed temperatures, but easy to do and to me they are more accurate.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 19, 2014 12:10PM
Do you have pull up resistors set in marlin?
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 19, 2014 12:54PM
Quote
ggherbaz
Using sensor 1 that is the correct type, connect brown to + blue to - and black to signal. Do M119 if shows triggered switch logic, do M119 and verify that is open, put a metal close to it and do M119 again should say triggered, if not, then you will have to used 12 volts and a voltage divider or LM7805 for signal to ramps.
Now this might be an stupid question: what kind of heated bed you have? Do you have enough metal there for the sensor to work properly?. I used capacitive sensors instead because they read any material and they read the top and not bottom of bed (glass), yes you need to have a table of offsets for different bed temperatures, but easy to do and to me they are more accurate.
I am not testing with my heated bed, so I will cross that bridge once I get the probe to switch logic. I am testing with an aluminum build plate that works with my Printrbot probe. I already connected them like that. I have not tried using 12V though. I do not understand why I would need 12V if the Printrbot probe works on Printrboard and RAMPS with 5V, but I will try 12V as soon as I get a voltage regulator.

Edited 1 time(s). Last edit at 10/19/2014 12:55PM by quillford.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 19, 2014 12:56PM
These are my settings. I believe they are enabled.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 19, 2014 12:57PM
Quote
ggherbaz
Using sensor 1 that is the correct type, connect brown to + blue to - and black to signal. Do M119 if shows triggered switch logic, do M119 and verify that is open, put a metal close to it and do M119 again should say triggered, if not, then you will have to used 12 volts and a voltage divider or LM7805 for signal to ramps.
Now this might be an stupid question: what kind of heated bed you have? Do you have enough metal there for the sensor to work properly?. I used capacitive sensors instead because they read any material and they read the top and not bottom of bed (glass), yes you need to have a table of offsets for different bed temperatures, but easy to do and to me they are more accurate.
Will this work?

Edited 1 time(s). Last edit at 10/19/2014 12:58PM by quillford.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 19, 2014 02:59PM
Yes, that's an LM7805. In general any regulator to 5volts will work. Since amperage isn't an issue, you don't need to have a heatsink on it.
Your pull ups are set right, but logics might need adjustment depending on type of sensor.

Edited 2 time(s). Last edit at 10/19/2014 03:05PM by ggherbaz.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 19, 2014 03:01PM
Quote
ggherbaz
Yes, that's an LM7805. In general any regulator to 5volts will work.
Ok. If this doesn't work, what do you suggest? Do you use an inductive proximity sensor?
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 19, 2014 03:16PM
Like I said, i'm using capacitive ones, but it's just a matter of preferences and settings. I also used higher distance sensing 10mm instead of 4, this will be specially important if you are under powering the sensor at lower voltages sensing distance might be reduced rendering the sensor useless.

To check the sensor with just a power source and a bulb, if the sensor lights up the bulb, the sensor is in working condition, if no just send it back as defective.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 19, 2014 03:23PM
[www.google.com]
This is a good video on how to test them.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 19, 2014 07:55PM
I figured it out. My RAMPS board was bad. I tried another one I had, and it worked.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 19, 2014 08:04PM
Good to know. Now you need to built two more printers to use the other sensors ;-)
Re: Auto Bed Leveling with an Inductive Proximity Sensor
October 19, 2014 08:53PM
Quote
ggherbaz
Good to know. Now you need to built two more printers to use the other sensors ;-)
I fully intend to.spinning smiley sticking its tongue out
Re: Auto Bed Leveling with an Inductive Proximity Sensor
February 02, 2015 05:23AM
I'm kind of late to this discussion...

I like a longer working distance for a capacitive sensor, but I was living under the impression that sensor repeatability is of the order of a few percent of the total scale. The video you suggested mentions a 2% repeatability, and if I use that then you get the measurement error within 0.2mm. I'd like the measurement error to be <0.1mm, but would like a longer working distance.

Can you comment on the repeatability of the capacitive sensor you are using? Maybe providing a part number?
Thanks.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
February 03, 2015 03:51AM
I use a heated bed PCB with an aluminium heat spreader on top and then a glass print bed. I had capacitive sensing working, but the capacitance is small and sensitive to both the thickness of the glass and to whatever coating you use on it to improve adhesion. As I swap glass print beds between prints, I wanted a solution that measures the distance to the top surface of the glass rather than the bottom surface. Inductive sensing would have had the same problem. I settled on a system using two infrared LEDs and one phototransistor. There are now about 100 Ormerod printers using one of my sensors, and most report good results. See [miscsolutions.wordpress.com] for more info and a link to the schematic and firmware.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
February 10, 2015 12:51AM
dc42,

I am working on my reprappro auto-leveling. It works great with an inductive sensor with an exception that the sensor has bad (~1mm) temperature drift. I tried Omron EESPY302 IR sensor and the repeatability was not good at all. It's not easy to find an inexpensive sensor with acceptable repeatability and temperature drift. I am waiting for a Fotek PS-15N sensor from Taiwan now.

Your solution sounds very interesting. Do you deal with temperature drift in firmware or hardware? I see you also experimenting with ultrasound sensor. I could not find a link to schematics on your website. Do you mind posting a link?
Re: Auto Bed Leveling with an Inductive Proximity Sensor
February 10, 2015 05:12AM
Quote
seavan
Your solution sounds very interesting. Do you deal with temperature drift in firmware or hardware? I see you also experimenting with ultrasound sensor. I could not find a link to schematics on your website. Do you mind posting a link?

You can find the schematics at [github.com]. I deal with temperature compensation for the ultrasonic sensor in the 3D printer firmware, see the S and C parameters in the G31 command description at [reprap.org]. However, I don't recommend the ultrasonic sensing, because if you use it when the bed is hot, the reading is affected too much by draughts. The sensitivity to temperature is a fundamental limitation of ultrasonic sensing, caused by the variation the speed of sound in air with temperature.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
February 10, 2015 06:57PM
Thank you dc42, I found the schematics.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
May 06, 2015 05:26AM
HI, I new in 3d printing and currently i'm having a new prusa i3 with Proximity Sensor, the issue is this sensor home correct but make my nozzle out of space, can anyone teach me how to move the nozzle to the home correctly, instead of sensor at home and nozzle out of heatbed, appreciate any kind person can tell me!
Re: Auto Bed Leveling with an Inductive Proximity Sensor
May 06, 2015 03:12PM
You need to measure your nozzle to sensor offsets in X Y and Z and your safe homing position in the bed and put those numbers in the configuration h file from your marlin firmware.

There are several online videos that explains in detail how to do it.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
July 12, 2016 06:10PM
I am trying to set this up. I have a Prusa I3 printer and changed to a OSOYOO MKS Base V1.4 3D Printer Controller remix Board.
I got an Inductive Sensor (LJ18A3-8-Z/BX 8mm Approach Sensor Inductive Proximity NPN NO Switch DC 6-36V)

I connected it to the 12V supply and put a resistive divider on the output to neg supply.
I measure the output after dividing it and it (not connected to board) reads 4.56 Vdc and
I put it on my aluminum bed, the light lites and the output drops to 0Vdc.
So I know the sensor is working. I connect it to the Z- input and the output starts at the 4.56Vdc and
when triggered it only drops down to 3.3Vdc which is too high to trigger the circuit.
I have removed all pullups and enabled all pullups...It doesn't seem to make a difference.

I do not know what to do next.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
July 12, 2016 07:56PM
Replace the resistors with a regulator. You have a circuitry on the board and it's altering the resistors value once is triggered.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
July 18, 2016 01:01PM
Why do people use inductive sensors when they are so limited compared for example to a capacitative sensor?
Is it because of size/weight or precision?
Re: Auto Bed Leveling with an Inductive Proximity Sensor
July 18, 2016 01:21PM
A capacitive sensor changes sensing distance with temperature and humidity. An inductive sensor doesn't do that.
Re: Auto Bed Leveling with an Inductive Proximity Sensor
July 18, 2016 01:49PM
Thank you.
So far I'm using a capacitative sensor as I had trouble making an inductive work with my bed.
May review it again when I change my printer bed.
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