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Leveled Bed >> Auto-Leveling Probe

Posted by isonoob 
Leveled Bed >> Auto-Leveling Probe
November 10, 2014 10:36AM
Anyone else agree? Recent put together a PrintrBot Simple Maker Edition kit that didn't come with a bed leveling probe, then purchased the upgrade kit for it and put a bed leveling probe in. Few days later, ditched the probe. Nothing beats a leveled bed smiling smiley thoughts? Is this a universal opinion or am is the inverse popularly agreed upon? I see a bunch of printers coming out now with bed leveling probes, which I guess makes it easy for the end user, but I think a leveled bed is some secret sauce
Re: Leveled Bed >> Auto-Leveling Probe
November 10, 2014 11:17AM
Well, I disagree with you. I've been printing for the last two months with a probe and to be honest I didn't even leveled my built plate when I put it together just to see how the probe will do.

Now few things need to be said about them, first is a constant in the reprap community to get the cheapest possible thing and also to under power them, I didn't pick a cheap one, I do not under power it and I do not use inductive, I use capacitive with a 10mm distance detection range and I powered with 12 volts.

The only thing I did was to generate a table for additional offsets based on temperatures, I use simplify3d and save these offsets on my processes.
I haven't had any failures and every once in a while I check that there is no mayor differences.

After two month of printing I'm in love with my probe.
Re: Leveled Bed >> Auto-Leveling Probe
November 10, 2014 12:19PM
Quote
isonoob
Nothing beats a leveled bed smiling smiley thoughts?
Well, not spending a lifetime leveling, and re-leveling, and then leveling some more because you transported your printer somewhere and in the process knocked something out of alignment might beat it. Think taking a printer to a show. It'd be great if you could sit it down, plug it in, and start printing, rather than re-leveling the bed.

I'm also pretty confident a large number of those that use such feature likely tried to level the bed previously, but in their particular case weren't able to get to a level nirvana like you have been able to achieve.
Re: Leveled Bed >> Auto-Leveling Probe
November 10, 2014 01:12PM
I do not have a probe just yet in my printer. However I can say this.

It is a nice to have feature. The bed does expand and contract with heat. I manually leveled my bed, it took me about 45 minutes to do so, with multiple tweaks to both the hardware and software.

I can say that auto leveling does not replace a properly built printer. If the printer shakes itself to bits or is not sturdy enough to hold its own weight, the auto level probe will help. However if the printer is very rigid it will only need leveling when you change variables like the bed, or sometimes the hot end. I have moved my printer, and sometimes hammered on it. It has never changed the alignment.


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Re: Leveled Bed >> Auto-Leveling Probe
November 10, 2014 07:02PM
doh! guess my views on bed leveling probe aren't so popular! probably why the shift towards manufacturers including them is happnening... Maybe ill dust off the ole induction probe and give it another chance
Re: Leveled Bed >> Auto-Leveling Probe
November 10, 2014 09:35PM
Besides the sensor, what else is needed/involved with adding a capacitive sensor to an Arduino/Ramps 1.4?
Re: Leveled Bed >> Auto-Leveling Probe
November 10, 2014 11:35PM
A normal capacitive sensor need 12V. So you only need 2 resistors for a voltage divider.
Something like this.

Re: Leveled Bed >> Auto-Leveling Probe
November 11, 2014 03:53AM
You can use the resistors or as I did a LM7805 5 volts regulator, it will be safer and more stable than the resistors alone.

Don't forget to set your pull up resistors in marlin or you will fry Your board.

Edited 1 time(s). Last edit at 11/11/2014 03:55AM by ggherbaz.
Re: Leveled Bed >> Auto-Leveling Probe
November 11, 2014 05:56AM
Quote
ggherbaz
Don't forget to set your pull up resistors in marlin or you will fry Your board.
Care to explain how not enabling the pull up resistor is going to fry the board?
Re: Leveled Bed >> Auto-Leveling Probe
November 11, 2014 07:54AM
Looking at these capacitive sensors on eBay, would I want a NO or NC.
Where would I find information on connecting, setup and calibration?
Would you use a 10mm if you were to do it over again.

Edited 1 time(s). Last edit at 11/11/2014 08:00AM by Easy.
Re: Leveled Bed >> Auto-Leveling Probe
November 11, 2014 08:30AM
Make your pick, but it is recommended a NC one for fail safe. But no matter which one you get, on marlin firmware you activate the pull up resistor and invert the logic based on either NC or NO.

It simple and just take few minutes to get it done and working.

Yes use the 10mm one, powered with your 12 volts, and it has 3 wires, Vcc, ground and signal. Vcc to 12 volts supply, ground to ground in ramps and signal to pin 1 of the LM7805 pin 2 to ground and pin 3 to signal on ramps,that's it, plain simple.

The LM7805 will not need a heatsink, and you can either bolted somewhere in the frame or use shrink tubing. And fix it to your sensor wiring.

My sensor: LJC18A3-R-Z/AX

Edited 3 time(s). Last edit at 11/11/2014 08:47AM by ggherbaz.
Re: Leveled Bed >> Auto-Leveling Probe
November 11, 2014 08:31AM
Quote
isonoob
doh! guess my views on bed leveling probe aren't so popular! probably why the shift towards manufacturers including them is happnening... Maybe ill dust off the ole induction probe and give it another chance

You just haven't had a sentient printer which can change it's own leveling on a whim. winking smiley

When I started researching to build/buy a printer I saw the self leveling systems and had the same thought you did, why should the bed have to be re-leveled after the initial build especially if I take great care and get it as close to perfect as possible. After a couple of weeks where I have had to re-level after every time I let it sit for several days or if I lift it up on one side to work on something easier, I've come to the conclusion that my printer is ether alive or possessed and that it's female. So if I don't pay attention to her or force her to do something she doesn't like, i.e. standing on one of her sides, she changes the bed settings to annoy me. eye rolling smiley So now I'm planning on setting up a bed leveling system soon.

Now if you don't mind the voices in my head want lunch spinning smiley sticking its tongue out
Re: Leveled Bed >> Auto-Leveling Probe
November 11, 2014 08:54AM
"Care to explain how not enabling the pull up resistor is going to fry the board?"

If you don't set your resistors in marlin, you will pass straight to ground 5 volts. Will this explanation makes more sense to you? . Do you know what happens when you connect together both terminals of a battery?

Edited 1 time(s). Last edit at 11/11/2014 08:58AM by ggherbaz.
Re: Leveled Bed >> Auto-Leveling Probe
November 11, 2014 09:21AM
If an open collector version of the proximity sensor is available, you would not need any additional circuitry, no matter what the operating voltage would be, if there is a built-in pull-up on the circuit board that you connect the sensor.... No?

Edit... I just found some diagrams on eBay from a vendor. It shows that a PNP device would switch from ground to open. It shows the NPN device as switching from open to Vcc.
I would think the PNP device would be preferred if the input board has a built-in pull-up resistor.

Edited 3 time(s). Last edit at 11/11/2014 11:09AM by Easy.
Re: Leveled Bed >> Auto-Leveling Probe
November 11, 2014 11:05AM
Quote
ggherbaz
"Care to explain how not enabling the pull up resistor is going to fry the board?"

If you don't set your resistors in marlin, you will pass straight to ground 5 volts. Will this explanation makes more sense to you? . Do you know what happens when you connect together both terminals of a battery?
I'm no EE, but you might want to double check what the purpose of a pull up resistor is.

The pull up resistor is between Vcc and the pin, not between the IO header and the pin. The pull up resistor, if enabled, holds the pin input high (reading 5V) until the circuit is grounded via a switch which causes the pin to read low (0V). If you don't enable the pin high, there is no 5V at the pin and the pin floats at an indeterminate state. You can supply 5V to the pin, or you can ground it and it's not going to make a bit of difference from a frying the board perspective.

Now if the pin was configured as an output pin, then yeah, you won't want to ground it directly without a load, but that would have absolutely nothing to do with the pull up resistor which only applies for an input pin scenario.
Re: Leveled Bed >> Auto-Leveling Probe
November 11, 2014 12:45PM
Found the info I was looking for here...

[www.thingiverse.com]

But I think selecting a PNP device would be better than the NPN device, as used in the above link. That way all you need to do is connect the output of device, select pull-up enabled, and then select normally open or normally closed. I think!
Re: Leveled Bed >> Auto-Leveling Probe
November 12, 2014 06:43AM
cdru,

Then i'm sorry for the misunderstanding, my thoughts were that without the pull up resistor the mega will throw the 5 volts straight to ground.

Edited 1 time(s). Last edit at 11/12/2014 06:44AM by ggherbaz.
Re: Leveled Bed >> Auto-Leveling Probe
November 12, 2014 08:46AM
Quote
ggherbaz
cdru,

Then i'm sorry for the misunderstanding, my thoughts were that without the pull up resistor the mega will throw the 5 volts straight to ground.

It will if the port is configured as an output, which can happen with run-away code. But as an input, the pull-up only connects the pin to the supply voltage though the resistor. This pulls the high signal up when the input is not ground, or low.
Re: Leveled Bed >> Auto-Leveling Probe
November 12, 2014 07:18PM
Ive been printing for a couple years and i can honestly say the auto bed level feature has drasticaly simplified printing. A level bed and having the Z height spot on for the first layer are two of the most important things to get a good print. The best upgrade ive made by far. Its a dream to be able to just click print and not have to stop the print and relevel the bed over and over and mess with resetting the Z home position etc etc.
Re: Leveled Bed >> Auto-Leveling Probe
November 13, 2014 07:22PM
Okay, now I am a little confused. It appears that NPN is the type output that switches from ground to open. So using a built-in pull-up resistor, I do not understand why a voltage divider is needed on the output of the sensor.
I have some NPN and PNP proximity sensors on the way so I will find out what is happening when I get them.
Re: Leveled Bed >> Auto-Leveling Probe
November 14, 2014 06:36AM
Quote

So using a built-in pull-up resistor, I do not understand why a voltage divider is needed on the output of the sensor.
The diagram in the thingiverse page is a PNP. It outputs 12V so a voltage dividier is necessary to drop it to a safer 5V level for the microcontroller to use. If you use a NPN sensor with a pull up resistor, that should work, you'll just need to supply more supply voltage to the sensor unless it's able to work at only 5V. The sensor specified appears to need 6V at minimum so it wouldn't be directly compatible with most boards that only have 5V with the endstop headers.
Re: Leveled Bed >> Auto-Leveling Probe
November 14, 2014 08:20AM
Quote
cdru
Quote

So using a built-in pull-up resistor, I do not understand why a voltage divider is needed on the output of the sensor.
The diagram in the thingiverse page is a PNP. It outputs 12V so a voltage dividier is necessary to drop it to a safer 5V level for the microcontroller to use. If you use a NPN sensor with a pull up resistor, that should work, you'll just need to supply more supply voltage to the sensor unless it's able to work at only 5V. The sensor specified appears to need 6V at minimum so it wouldn't be directly compatible with most boards that only have 5V with the endstop headers.

I guess I am really showing my age by how confused I got with this whole thing. Somehow I got the impression an NPN device was being used, then I got confused on the output of NPN and PNP devices.
Anyway, I am going to try to use an NPN device, since it should not need any signal conditioning (just the pull-up enabled), NPN is safer (shorting signal to ground does not hurt it), and you can safely tie multiple NPN outputs together.
There is probably a good reason why a PNP device is being used. I guess I may find out why.
You should be able to operate an NPN device at its maximum operating voltage without regard to the signal voltage because it only switches from ground to an open circuit. There is no voltage output, the pull-up resistor on the input device sets the high signal voltage.

Edited 2 time(s). Last edit at 11/14/2014 08:23AM by Easy.
Re: Leveled Bed >> Auto-Leveling Probe
November 14, 2014 10:19AM
Quote
Easy
There is probably a good reason why a PNP device is being used. I guess I may find out why.
It's just a personal decision when designing a circuit. Are you sinking or sourcing the signal? It's not that one is better or worse than the other, it's usually where is the transistor places in relationship to the load, supply, and ground.
Re: Leveled Bed >> Auto-Leveling Probe
November 22, 2015 09:18AM
So let me get this right. The NPN sensor works fine if you have the signal wire going to the signal pin of the Z endstop on ramps and the + and - to the 12v input on ramps? PNP would need the 10k ohm and 15k ohm resistors correct?
Re: Leveled Bed >> Auto-Leveling Probe
December 12, 2015 10:30PM
guys i trying use autobed leveling in prusa i3 printer and i bought 10mm sensing length NPN Normally closed see the image and give me the Marlin setting
please help
thanks in advance
Attachments:
open | download - 20150423165810.jpg (372.7 KB)
Re: Leveled Bed >> Auto-Leveling Probe
December 12, 2015 10:32PM
guys tell me should i go for NPN or PNP because i want use with RAMPS 1.4
Re: Leveled Bed >> Auto-Leveling Probe
December 14, 2015 12:49AM
NPN.

No extra components required.

When I was setting one up for a friend he was very nervous about having no extra components, so we put diode in series with the signal line of the sensor. This worked just fine.

I'd avoid using a resistor voltage divider, because unless you understand what the pullups are doing inside the arduino chip, you can stop the signal making its way into the arduino altogether.
Re: Leveled Bed >> Auto-Leveling Probe
December 18, 2015 12:51PM
This is a choice, npn is easier to setup but if the sensor fails you'll get a head crash as the signal never appears when the bed is near the sensor and the standard open voltage 0v stays at 0v. Some sensors of this type will work on 5v so you can connect it to your endstop pins on ramps directly. The sensing distance is reduced and the triggered led might not work but its very easy.

With pnp the standard open voltage once regulated (see below) is 5v and it switches to 0v when triggered. So if the sensor fails the printer reads triggered and the z motor/s stop. So no head crashes.

Avoid voltage dividers use a voltage regulator for the signal pin. It costs very little and its very easy to wire and reliable.

Edited 1 time(s). Last edit at 12/18/2015 12:54PM by DjDemonD.
Re: Leveled Bed >> Auto-Leveling Probe
December 20, 2015 07:40AM
Just another perspective:

I have not had to level my bed in over a year. I have my printer tuned in to the point I can power on and print.

And on the flip side, this same printer has a 0.3mm backlash on the Z axis. It is repeatable and only occurs when reversing direction. Since my slicer setting is to raise 0.3mm at the very beginning of a print, it compensates that backlash and it does not effect the print. But when I installed auto-leveling and purposely tilted the bed, it was a mess.

I guess what I am saying is that auto-level really depends on the printer itself, not a generic 'this is better than that'. And I am glad there is a solution for those that have beds that keep moving out of level.


"Never argue with stupid people, they will drag you down to their level and then beat you with experience."
Re: Leveled Bed >> Auto-Leveling Probe
December 20, 2015 04:27PM
I'm also pretty confident a large number of those that use such feature likely tried to level the bed previously
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