M135 or Alternative

wayneosdias

I have a PNP machine using 6HC/Openpnp. Vacuum sensing is handled by temp0 and temp1. The temp sample freq is too slow for part detetcion or Z probing. I found M135 and https://forum.duet3d.com/topic/16698/m135-deprecated.

Is there any way to increase the temp sample freq >50hz? Or is there any other 6HC peripheral that is capable of sampling 0-5v single ended signal at >50hz?

dc42

@wayneosdias are you able to use a digital sensor to detect whether the pressure indicates successful pickup, instead of an analog input?

wayneosdias

@dc42 I currently only have SE analog 0-5v for vac measurement. An atd to spi or i2c I guess would be possible, but then I would have to move the measurement circuit alot closer to the 6HC and away from the valves.

What would the max atd frequency be?

dc42

@wayneosdias the ADCs in the Duet sample very quickly, however the Heat task that reads temperatures is only scheduled every 250ms.

One way that you could get a faster response from one of the inputs is to configure it as an analog Z probe instead of a temperature input. You will then be able to query whether it is triggered or not at a much higher rate. However, RRF supports only a single analog Z probe, so this would only handle one of your two channels.

A solution to this would be for us to extend the firmware so that the M950 command with J parameter can be used to create an analog input and either report the analog reading or set a threshold and hysteresis for on/off detection. You are welcome to raise a feature request for this, however I can't promise that it would be implemented any time soon.

Perhaps the simplest approach for now would be to purchase a couple of comparator modules similar to https://www.amazon.co.uk/ioannis-3-5-24V-Comparator-Indicator-Control/dp/B0BTGZ1BW to convert the 0-5V signals into digital signals.

wayneosdias

@dc42
Hmm, What about the first option of using the Zprobe along w an analog signal switch between my two measurement channels? A Openpnp script could handle the M42 ch switching and the Duet can just stream the single adc value.

Extending the M950 per my pull request would never happen 2nd my lack of follow through

The comparator wont work as each nozzle tip size generates three different levels, ambient, vacuum part on, vacuum part off.

Ill need to read more about Zprobe. Thanks for the tip!

dc42

@wayneosdias you need to use M558 with parameter P1 to configure an analog Z probe. Then use the G31 command to set the threshold on a scale of 0 to 1023.

HTH David

wayneosdias

@dc42
Thanks David. I'm rethinking the problem. The issue I was trying to solve was potential 'tool' offsets of different pnp nozzle tips during mid job tip changes. The CP40 tips themselves are all similar length but tip to nozzle mounting depth seems to vary a tip change to tip change. Vacuum threshold was going to be the probe feedback.

I not familiar w tool offsets in Openpnp, but that's not what is bothering me. The inconsistent mount depth of the CP40 is. I'm going back the Juki tips that I am familiar with them and they firmly mount at consistent lengths. Probing for the Juki tips isn't needed.

Thanks for the tip.