Mini IR Sensor Intermittently Triggering Too Far From the Bed

A Former User

I AM NOT LOOKING FOR 3RD PARTY SUPPORT this notification is for reference of the Duet Team only.

I have 6 Duet-3 Boards All on Core-XY Machines with LC-1 Tool-Boards and I only Run the Mini IR sensor for homing/levelling the Z axis

Randomly this means it DOES NOT DO IT ALL THE TIME so it is NOT a config file issue....

Randomly they all trigger 12.5mm early, I have homing configured to drop the bed by 5mm after homing has completed, DWC reports the height as normal say 5.42mm as an example, but it is plainly clear that the head/probe/nozzle (whatever you want to pedantically call it) is further from the bed than DWC is reporting, if you manually drive the bed up until DWC displays 0mm and measure the distance left, the extra offset is always 12.5mm.

I previously thought it might be the fact that at the time I was initially looking at this issue the IR outdated (now fixed) docs (incorrectly) stated that the trigger value should be around 500, when with probe type 8 on the Duet-3 it only ever shows a value of 1000.

I can manually overcome the issue by sending a G92 Z30 command and then driving the bed up until it is less than 5mm from the probe and then re-homing the Z axis and this time the probe triggers at the correct height.

It’s not the bed surface as this occurs on a few different surfaces and if it was the bed surface the problem would manifest all the time instead of intermittently, and I dont have dark coloured beds with white contrasting grid squares.

So after my previous issue of prints randomly stopping (which DC42 advised might be the tool-board firmware crashing) an update of the duets and tool-boards to the latest beta firmware seem to have cured that issue, and it initially appeared that my random early IR triggers were gone too.

Last night I homed one of the printers and the early triggering occurred....... So extremely peeved I went to bed and this morning I changed out the tool-board (I keeps spares of everything on the shelf) I updated its firmware to the newest but I still got the early trigger.

As I run 4 wire RJ11 cables up to the head but only used 2 I had spare wires going to the head I connected 1 to an io.in on the Duet-3 main board and the other end to the signal wire on the Mini IR Sensor, and reconfigured M558 to reflect the change.

A quick macro later and nearly an hour of me standing watching the Z axis repeatedly home, not once did the sensor trigger early....

I re-wired the other 2 of the other 5 (those 3 are still printing) the same way and they appear to no longer be triggering early either.

dc42

When did you purchase the IR sensors? There was a firmware change some time ago to eliminate the false triggering that sometimes occurred with some bed surfaces.
Does the false triggering correlate with a low sun visible through the window, with no clouds in front of it?

Veti

@dc42 said in Mini IR Sensor Intermittently Triggering Too Far From the Bed:

When did you purchase the IR sensors? There was a firmware change some time ago to eliminate the false triggering that sometimes occurred with some bed surfaces.

where is the firmware for that?
on https://github.com/dc42/OrmerodSensorBoard/tree/master/Firmware/Mini-differential-IR/V1.2
the last change was 4 years ago.

A Former User

@dc42 said in Mini IR Sensor Intermittently Triggering Too Far From the Bed:

When did you purchase the IR sensors? There was a firmware change some time ago to eliminate the false triggering that sometimes occurred with some bed surfaces.

Does the false triggering correlate with a low sun visible through the window, with no clouds in front of it?

All my IR sensors are either purchased direct from the Duet website or E3D, purchased my last batch about a year ago (they are all SMD mounted components) and they came from E3D

My printers are in my workshop it has no windows. Only diffused artificial light.