Welcome! Log In Create A New Profile


Proximity sensor value check

Posted by IPushedHumpty 
Proximity sensor value check
July 07, 2015 01:11PM
Hi ladies and Gentleman, boys and girls, tech gurus of all ages,

I need some advice please. I was given an "Ormerod 1" however during the commissioning stage I'm getting an unusual value from the proximity sensor. I'm new to 3D printing and engineering so I might just be being overly cautious so forgive me if this is the case. I've searched the message board posts but couldn't find anything like this, only when values are greatly in excess or refusing to change when covered, so any advice would be greatly appreciate.

With Z-axis 20-30mm away from the base running G31 command; In a sunlight lite room the values returned are around 150-250. In a dark room values of 75-100. And with white paper up to the sensor I get the correct range of 940-980.

I've checked the wiring and connections which seems to be ok, as well as making sure the blue wire is on pin 6 rather than 9 of the expansion header since my firmware is updated to 1.09 on both the SD card and hardware (I did also check it against pin 9).

Am I OK to still run with figures like 75-250 or am I correct in assuming something wrong since the guide states values averaging 20 should be returned. I read that if the results where remaining constant then it is most likely a problem with the ADC caused by a short, although since mine is giving me the correct sensor reading when the PS is covered I am assuming this isn't the case. I'm going to check the PS with a multimeter later today however if this is working ok is there anything else you can suggest?

Sorry if this is a dumb question.

I have attached pics just in case you spot something I have missed.

Edited 2 time(s). Last edit at 07/07/2015 01:14PM by IPushedHumpty.
open | download - Results.jpg (164.4 KB)
open | download - Duet.jpg (319.8 KB)
open | download - PS close.jpg (150.8 KB)
Re: Proximity sensor value check
July 07, 2015 10:39PM
Scratch that. seems to be working now.
Re: Proximity sensor value check
July 08, 2015 02:55AM
The Ormerod 1 proximity sensor is notoriously sensitive to background IR, such as incandescent lighting and bright sunlight. Fixes (in order of increasing expense):

1. Use the printer in a room with only fluorescent or LED lighting, and draw the curtains if it is a bright sunny day.

2. Add modulation to the sensor. I posted a thread about how to do this over a year ago.

3. Buy a modulated sensor and new sensor loom from RepRapPro. Modulation reduces the sensitivity to ambient IR by a factor of about 15.

4. Buy one of my Ormerod hot ends boards. This includes a proximity sensor that uses 2 beams of IR to eliminate sensitivity to background IR. It works on almost any print surface, so you don't need the white targets and you can use it anywhere on the bed. It also includes thermostatic control of the hot end fan.

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

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Sorry, only registered users may post in this forum.

Click here to login