Finally got the auto-leveling/tramming feature working. Sharing my experience.
@Anan_Leelasmanchai I’m using Slic3r to produce the gcode. File preparation can help achieve a tighter tolerance but it’s dependent on the build quality of the printer and how well the extruder is tuned at. Holes still pose a problem due to the way slic3r produces it’s toolpath. Although, I was able to lower the clearance from 0.5mm to 0.3mm.
Interesting. I ordered a similar one (PS-05N) that should arrive tomorrow. I have an aluminum bed, but I use glass on top of it. It takes longer to heat up, but broken window glass is easy/cheap to replace. So you just hook it directly to the Printrboard’s Z-stop?
Semi-related: I bought a different sensor last year but it was much heavier than I expected. Just this weekend I got the idea of connecting it to a spare Arduino UNO, get readings from it, manually adjust the bed, and then remove the whole setup (no added moving mass). It seems to stay set pretty well, so it might be ok, but after seeing this post I may skip all that and just use the new lighter weight one like you’ve done.
This is the one I bought last May:
This is the one I ordered a few days ago that should arrive tomorrow (similar to yours):
http://www.amazon.com/gp/product/B00FZUECJA/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
EDIT:
And this is the one I may yet buy, since it seems to the be the same one you used:
@SirGeekALot I actually tried that method using the sensor as a way to manually adjust the bed. It worked but doesn’t beat the paper leveling.
This is the sensor I bought. The rated DCV is 4.8-30 and you want it just around 5V. You may have to step the voltage down on yours but it might work at 6V but don’t take my word for it. Once you set the firmware, it’s ready to go. Although, you will have to familiarize yourself with the auto level gcode command and editing your start gcode. I ran into a problem where the z offset would not save using the m212 command. Had to write the z offset in my start gcode
@Chris_Lau I must’ve been tired when ordering…twice. This may explain the resolution problems I’ve been having with the first sensor. The analog read kept showing values of about 140-190. I had been considering attempting to amplify the sensor output range with a cheap transistor (2N3904/2N3906). But now, looking at the input voltage range, I think the voltage being too low is the cause–just not enough power to drive it properly. So, I probably just bought the wrong damn thing. Hmmm…I wonder if I could just power it from the 12V rail and still read it from the Arduino’s analog read pin…without frying the Arduino?
@SirGeekALot : See @Thomas_Sanladerer video about auto-tramming (linked above) - you should use a level shifter (may be done with two resistors or other HW) to drop the voltage from 12v to 5v signal. Also, I would recommend ditching the metal threaded ‘case’ (cut/file it off!) to reduce weight - you don’t want that much weight hanging on your print head… I sill haven’t decided on which sensor to buy…
@Nuno_Lourenco thanks but I already connected it directly to the end stop and it works as is, so no modification needed.
@Chris_Lau I downloaded the latest Marlin firmware for Printrboard from Printrbot’s github and then updated it similar to your instructions–thanks! But I keep getting an “endstops hit” error when I issue the G29 command. Did you have this problem? Any ideas?
I just tried uncommenting DISABLE_MAX_ENDSTOPS, but I still get the same error, and M119 shows the only endstop triggered is Z.
Output:
SENDING:G29
Bed x: 50 y: 155.00 z: -4.77
Bed x: 50 y: 50 z: -2.77
Bed x: 155.00 y: 50 z: -2.34
echo:endstops hit: Z:-2.34
M119
SENDING:M119
Reporting endstop status
x_min: open
y_min: open
z_min: TRIGGERED
Nevermind. That seems to be just an innocuous debug message, because after putting a G28 and G29 in my starting gcode, it probes and continues to print just fine. I can even see some slight z-axis movement, so it is compensating for my non-trammed (but flat) print surface. Yaay! 
@SirGeekALot Good to hear it’s working!
Looks great!