IR Sensor problem

brian

I replaced my ir sensor a few months ago and it has been working ok. Then suddenly it no longer stops when it reaches the proper distance from the bed. So i thought it was somehow defected and purchased another from (Filastruder in the states). I installed it today and it does exactly the same thing. When the z is homing it slows down at the same position as it always did, but then doesnt stop. I made no changes to the config.g or anything else before this happened. At start up the ir sensor flashes 4 times. All the wiring is the same as before. Here is my config setting:
M558 P1 H3 F200 T1000 ;smart IR Z probe, (H)dive height 3mm, probe speed 200mm/min, travel speed 5000mm/min travel speed
G31 X0 Y0 Z0 P500

Firmware Name: RepRapFirmware for Duet 2 WiFi/Ethernet
Firmware Electronics: Duet WiFi 1.02 or later
Firmware Version: 2.02(RTOS) (2018-12-24b1)
WiFi Server Version: 1.23
Web Interface Version: 1.22.6The controller is Duet

Phaedrux

Is ambient lighting the same?

brian

@phaedrux yes

Phaedrux

What's the bed surface? Can you post a photo?

dc42

@brian please check that the height of the bottom of the sensor board above the tip of the nozzle is correct, about 1.5mm. When using an uncoated glass bed backed by black paint or black paper, the sensor should trigger when the bottom of the sensor board is between 2.5 and 3.5mm above the bed. That distance will be a little different for other bed surfaces, in particular it is higher for opaque surfaces.

brian

@phaedrux glass, i use sticky white labels on the home area, has worked for years. will try to upload a photo

brian

@dc42 ok i changed the distance from 4 mm to 1.5 mm and that worked. Thanks. Dont know why it worked so long before.