BL Touch Self Test Speratic
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On power up I see that some times the BL touch will run a self test and other times it will not. When it does not self test it will not extend during the Z home. If I power cycle the printer once or twice the BL touch will then self test and work properly.
Is it possible that there is a background command being issued at startup that may be preventing the self test?
Is it possible to add logic to the home routine to check that the pin is extended? I know that the trip value P is set in the G31 command, is it all possible to interigate the P value manually? My thought process is to extend the probe, wait some time, then check that P is equal to some value, if not error.
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Hi,
Did you try adjusting the grub screw at the top of the unit?
Check the docs for how this is done.
Frederick
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I'll give their manual another read. I thought that set screw just adjusted sensitivity.
It still would be nice to have positive feedback on the extend with it being so critical for homing.
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Hi,
I mentioned the grub screw because that is the only adjustment that you can make - it may or may not help but what else can you do.
Did you add an "Alarm Release" command to your config.g file?
Frederick
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It could be a loose wire connection or failing probe. Having a spare probe to test against isn't a bad idea.
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I replaced the BL touch unit and I still this. I've also seen this on separate printers. And I've quadrupedal checked the wiring. If i power cycle 2-3 times the self test will run and everything works fine. If I then power cycle again the unit will not do anything and no commands will work. If then disconnect and reconnect the two power pins the self test will perform.
Looking at the BLT timing diagram I see that there is a minimum 100ms delay before setting PWM so an internal power check can be run. I'm running using a 24 V power supply for the duet and a seperate 5V power supply for the duet logic. Is it possible that there is some power delay on the 24V or 5V side of the board which is cutting into that 100ms wait time.
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I disconnected the PWM cables and powered the BL touch direct from my 5V power supply. I still see the same results of the self test only occasionally being performed on power up. Looks like it is an issue on the power side.
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Did this ever get sorted out? I am having issues with my BLTouch not deploying off my Duet3/Toolboard setup.
My BLTouch clone self tested fine, updated to a Genuine BLTouch v3.1 and now no self test... -
I found that the 5V signal to the BL touch was not instance on, but instead "slowly" ramping up to 5V. The BL touch was not seeing 5V fast enough and going in to error. I added a time relay to create a slight delay before powering the bl touch and it remedied my situation.
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@Eduma Thanks - a time relay is not realistic on the Toolboard, so I'll just have to run with it
Appreciate you sharing your solution though! -
@I_Jedi said in BL Touch Self Test Speratic:
@Eduma Thanks - a time relay is not realistic on the Toolboard, so I'll just have to run with it
Appreciate you sharing your solution though!There is a servo position you can send to the BLTouch to force the self-test.
Frederick
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@fcwilt Thank you... the question at hand is should the BLTouch automatically do an unprompted self test as soon as it has power. Several of us are having an issues with the v3.1 on the Toolboard. There is a suspicision that it is not getting sufficent 5V immediately during boot up to run test. So fallback appears to force a M280 P0 S120 in the startup gCode
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@I_Jedi said in BL Touch Self Test Speratic:
@fcwilt Thank you... the question at hand is should the BLTouch automatically do an unprompted self test as soon as it has power. Several of us are having an issues with the v3.1 on the Toolboard. There is a suspicision that it is not getting sufficent 5V immediately during boot up to run test. So fallback appears to force a M280 P0 S120 in the startup gCode
Well put. I have confirmed the same behavior with the toolboard.
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I am also still investigating why the BL Touch goes into an alarm state (blinks red) so often when connected to the toolboard even though everything appears to work fine and it responds to all commands..
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@oozeBot I am not quite that far... still finishing first time start up... That is quite frustrating. I hope we get someone from Duet to let us know what to try/look for/patch firmware...
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Hi,
I would imagine the probe is not seeing the power conditions that it expects to see on power up and is behaving oddly.
I would use the "reset" and/or "self test" commands as needed.
Frederick
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@fcwilt said in BL Touch Self Test Speratic:
Hi,
I would imagine the probe is not seeing the power conditions that it expects to see on power up and is behaving oddly.
I would use the "reset" and/or "self test" commands as needed.
Frederick
This does not appear to be a reliable fix. In fact, M280 P0 S160 doesn't even clear the red flashing state most of the time. I'm ignoring it for the moment but really want Duet to weigh in..
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@fcwilt the real thing - v3.1. In fact, I purchased two more this past week and both are exhibiting the same behavior when connected to the toolboard.
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@oozeBot said in BL Touch Self Test Speratic:
@fcwilt the real thing - v3.1. In fact, I purchased two more this past week and both are exhibiting the same behavior when connected to the toolboard.
Sounds like some compatibility issue between the toolboard and the BL.
Now this doesn't address the problem BUT I've recently replaced my BLTouch v3 units with 12 mm inductive sensors. They take a little bit more space but the results are better than I ever got with the BL units. And they don't click.
Frederick
