Time of reaction Duet2 board on Z probe ouput

olee

I am developing an effector similar to Smart Effector for using my dc42 Kossel as an automatic solder paste dispenser. I use LSM6DS3 accelerometer chip as Z probe. At the moment it works pretty well for me and triggers an output within 1-2 milliseconds after plastic TT needle touches the bed or board on it. I use E2Stop input on my Duet2 Internet controller as Z probe input, P4 probe type in M558 command.

Everything worked satisfactory but there is a problem: time delay between my probe output and start of reaction the system is about 9 milliseconds. It is somehow long for my case (plastic needles is a delicate matter). As I understand it all Z probe inputs have some sort of filtering on them except the dedicate Z probe input on Duet2 board at P8 probe mode. But I don’t disconnect the Smart Effector when using my own effector, so if I want to use this dedicated input I need some sort of combining circuit.

So that is a question: what is the time of reaction difference between filtered and unfiltered inputs and is there any sense to mess with an additional circuit?

dc42

@olee you can use mode P8 with any spare input on Duet 2. The endstop inputs on Duet 2 have a small R-C filter on them but the additional inputs available on the expansion connector don't.

olee

@dc42 , thank you. If I understood it correctly M558 P8 C5 ... would work for me? I use firmware 2.05

droftarts

@olee said in Time of reaction Duet2 board on Z probe ouput:

M558 P8 C5

Yes, I think that should work with E2_STOP on the expansion header.

Ian

olee

@droftarts , sorry guys, but P8 probe mode doesn't work on E2Stop input (M558 P8 F1200 H5 R0.4 C5). Duet2 doesn't see any signal from probe even constant high level and P4 works perfect. So not a remedy for me.

droftarts

@olee For P8, you need to use the Z-probe connector, I think. According to the info on the RRF 2.x tab here https://docs.duet3d.com/en/User_manual/Connecting_hardware/Z_probe_connecting#z-probe-modes-selectable-in-firmware
Mode 8 is unfiltered version of mode 5, which is like Mode 4 but the probe connects to Z Probe input. This is specific to RRF 2.x. In RRF 3.x, mode 8 can be used on endstops.

Ian

olee

@droftarts thank you. It was the reason I start this topic. Initially I was sure that only Z probe input allow P8 mode and I want to evaluate benefits of making extra circuit to combine outputs from two sensor and if extra work gives some prize for me. But dc42's reply gives me a hope to get it without extra work. Alas, now I am at the start of the problem now so if it is possiblle please clarify timing difference between filtered and iunfiltered mode. I am not ready to change to RRF 3.x version yet.

dc42

@olee I don't remember the details for RRF2 but AFAIR the mode (P parameter) in RRF 2 defines both the type of probe, whether filtered or not, and the pin it connects to. Whereas in RRF3 the pin is a separate parameter and you can use any suitable pin. S in RRF2 I think you can only use the Z probe pin.

I'm surprised that the reaction time using the E2Stop input is as long as 9ms. If the accelerometer output is open drain then adding a pullup resistor to +3.3V may help. Try about 1K to 4.7K.

olee

@dc42 according to documentation in RRF 2.x P define a type and sometimes a pin too. P4 define type and pin is defined by C parameter. 9 ms is the time between my probe output (pushpull type) to reaction of the printer visible at accelerometer output so maybe it is the dynamics of my printer mechanics that determinied this time. If you consider that time is very long I am apted to the last so I try to live with it for awhile. Anyway thanks for all responses