Z-probe as external trigger?
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Hi, I'm using a load cell as a Z-probe on my system. I would like to configure an external trigger such that if the load cell value reaches a certain analog value, it triggers an e-stop. This is mostly for safety to avoid damaging the load cell if something goes wrong.
Is this possible? Thanks.
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@soccerpaul said in Z-probe as external trigger?:
Hi, I'm using a load cell as a Z-probe on my system. I would like to configure an external trigger such that if the load cell value reaches a certain analog value, it triggers an e-stop. This is mostly for safety to avoid damaging the load cell if something goes wrong.
Is this possible? Thanks.
If you use trigger 0 then when activated it will perform an emergency stop.
Frederick
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@fcwilt The issue isn't so much the emergency stop part, but using the z-probe's analog signal to trigger, for two potential reasons:
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The M581 command seems to only support digital inputs, not analog. I found this firmware request for an analog trigger from 2019 (https://forum.duet3d.com/topic/11549/analog-threshold-for-m581-trigger) but don't know if this has been implemented.
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Using a specific pin name for M581 seems to no longer be supported. You first have to define the IO to use with the M950 command. I'm not sure if it's possible to use M950 with the same pin as the Z-probe or if this causes problems. I tried and didn't see the sensor appear in the object model.
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@soccerpaul said in Z-probe as external trigger?:
@fcwilt The issue isn't so much the emergency stop part, but using the z-probe's analog signal to trigger, for two potential reasons:
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The M581 command seems to only support digital inputs, not analog. I found this firmware request for an analog trigger from 2019 (https://forum.duet3d.com/topic/11549/analog-threshold-for-m581-trigger) but don't know if this has been implemented.
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Using a specific pin name for M581 seems to no longer be supported. You first have to define the IO to use with the M950 command. I'm not sure if it's possible to use M950 with the same pin as the Z-probe or if this causes problems. I tried and didn't see the sensor appear in the object model.
I think you will have to devise an external circuit/device to monitor the analog output of the load cell and generate a digital signal at the desired load.
Then you can pick any digital input using M950/M581.
I cannot think of any other way to do it with the current firmware (3.4).
Frederick
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@fcwilt That's what I was thinking as well, but I was hoping I had missed a simpler way of doing things. Thanks for your help.
