Posts made by SnowCrash

@dc42 said in Laser Filament Monitor 'SW' PCB Pads - Unsolved:

@snowcrash said in Laser Filament Monitor 'SW' PCB Pads - Unsolved:

Ok, so... was my original understanding correct? that is, the voltage reading between the 2 pads (High/Low) serves as an indicator for filament present/not-present?

Our intention is that if you want to add a filament presence switch, you add a switch that shorts those 2 pads together when filament is present.

To make it easier for us (or anyone else) to prototype new functionality.

In what why exactly? could you please give an example?

No, because we haven't used them yet.

Ok, thanks

@dc42 said in Laser Filament Monitor 'SW' PCB Pads - Unsolved:

@snowcrash said in Laser Filament Monitor 'SW' PCB Pads - Unsolved:

If I bridge the SW 'jumper-pads' (J1) - then the Signal Output (i.e. OUT on P1) becomes a binary output, that is, High for 'no filament' & Low for 'filament present' (or, perhaps, vice versa)?

No. One of the 16 bits in the position report returned to the Duet is the switch status.

Ok, so... was my original understanding correct? that is, the voltage reading between the 2 pads (High/Low) serves as an indicator for filament present/not-present?

Also, what is the purpose of the M2 pads (according to the schematics they bridge PA0 & PA1 on the ATtiny)?

To make it easier for us (or anyone else) to prototype new functionality.

In what why exactly? could you please give an example?

I had another look at the schematics for the filament sensor and I'd like to know if I got this straight (it seems like my previous understanding of the SW pads' function wasn't right):

If I bridge the SW 'jumper-pads' (J1) - then the Signal Output (i.e. OUT on P1) becomes a binary output, that is, High for 'no filament' & Low for 'filament present' (or, perhaps, vice versa)?

Also, what is the purpose of the M2 pads (according to the schematics they bridge PA0 & PA1 on the ATtiny)?

Thanks.

@dc42 said in Laser Filament Monitor 'SW' PCB Pads & Inner Chamber Color:

A filament presence switch is a simple switch that tells the sensor whether filament is present or not. So it can tell the Duet instantly when a spool runs out. But it's not really needed, because the end of the filament will pass through the filament monitor, which should detect loss of motion before the end reaches the extruder drive.

So the voltage across these pads alternates between High & Low on the basis of filament presence regardless of the main signal from the monitor module? does this functionality exist out-of-the-box or are tweaks needed?

@dc42 said in Laser Filament Monitor 'SW' PCB Pads & Inner Chamber Color:

1. It's for an optional filament presence switch.

Thanks for the very quick response, @dc42!

Could you please elaborate on what 'an optional filament presence switch' is and what it does?

Hi,

I got Duet's newly released laser filament monitor a while back but only now starting to look into hooking it up in my rig & I have the following questions which I'm hoping to get some info on:

(1) on the sensor's PCB there are a couple of round pads marked 'SW'. Looking at the schematics they seem to me to be intended for connecting an external reset switch - is this correct? and if so, has anyone utilized this feature? How useful is it to have?

(2) What would be the best background color (if any) for the inner chamber where the sensor's 'camera' chip is located (i.e. where the filament runs and inspected by the chip)? does the color even make a difference in this context?

Many thanks in advance.
SnowCrash

Thank you, @phaedrux! as always, an excellent comment & very useful info

@phaedrux said in Help with Steps per mm Calculation:

If you're set on using those 12mm pitch lead screws I don't think 533.3 steps per mm will be very detrimental to you. Is that the only pitch option available in that diameter?

I'm currently undecided as I'm not sure the gains in resolution would be worth the expense.

As for lead-screws with other pitches, those are the only ones (apart from the 10x25 I have) with a 10mm diameter I could find on Igus. I tried looking in other places, but so far haven't found anything suitable.

And as I mentioned above, I'd rather stick with the 10mm diameter to avoid the need to replace a whole set of bearings.

So if anyone has a recommendation for good quality lead-screws at a decent price with 10mm diameter, I'd be very interested to hear it.

@phaedrux said in Help with Steps per mm Calculation:

I forgot to address your question about increased resolution between the 12mm pitch and 25mm pitch lead screws. The difference for a Z axis would mean different amounts of travel per step.

Using Z_steps_per_mm = (motor_steps_per_rev * driver_microstep) / thread_pitch

motor_steps_per_rev	400
driver_microstep	16
thread_pitch	25
Z_steps_per_mm	256.000000
travel_per_step	 0.003906250 

Versus

motor_steps_per_rev	400
driver_microstep	16
thread_pitch	12
Z_steps_per_mm	533.333333
travel_per_step	 0.001875000 

Those are both really odd layer heights. I personally wouldn't use either lead screw for a Z axis, but if they are for other axis, it would matter a lot less.

At the risk of sounding incredibly foolish, I thought that with 400 steps per revolution on the side of the steppers, and 25mm per revolution on the lead-screw & nut side, my minimum layer height is 25/400 = 0.0625mm. Am I totally wrong on this? (btw, Is it relevant that my printer is a Delta type in this context?)

Thanks for the comment, @fcwilt, but that's not what I meant by my question. I was referring to the pro's and con's of switching from 10x25 lead-screws to 10x12 ones.

@aidar said in Help with Steps per mm Calculation:

Above calculations use 16 microstepping because you wrote you use 16 interpolated. This may looks like 256 , but it isnt. Calculations for steps per distance are made in processor, so it use this 16 value, interpolation is made after in driver by splitting each microstep to 16 more steps again. Or something like that. Anyway, if you use 16x interpolated or 256x its kind of same for motor, but not same for processor calculations. I hope it make sence, howevwr i have to say sorry for my bad english once again.

Thanks @aidar, that definitely helps.

Am I correct in understanding that this way - i.e. x16 microstepping with interpolation (giving 256 in total) - is the right way to do it with the Duet? That is, the best way to get max resolution from the steppers?

@sigxcpu,

Actually that is "lead". I find it amazing that Igus confuses "lead" and "pitch" ... That P is clearly "lead", not "pitch". The pitch is the axial distance between adjacent threads. They measure the "pitch" as distance between the ridges of the same thread, which actually is the "lead" - axial advance after you turn the screw 360 degrees (1 turn).

Thanks for the clarification! makes me feel a bit better about having such a hard time getting my head around this

And, last but not lease, I'm still looking for advice on the above open question so any comments would be welcome:

any thoughts on the potential increase of resolution (from 256 to 533 steps/mm vs losing the round numbers for steps and having slower movement overall?

Thanks for everyone who replied!

That's a really interesting discussion and I think it illustrates perfectly why it tends to get my brain twisted up with all the terms, partly because...

@aidar said in Help with Steps per mm Calculation:

@dougal1957 Got it. But i am sure by 25mm and 12 mm OP means lead then, not pitch.

Actually, I did mean 'pitch' rather than 'lead' - and I'm not going by what I know here (as I know close to nothing on this), but by the documentation.

Also, notice that I didn't use the term 'lead', but rather 'number of threads', as this is what Igus use in their listing, although I do believe they mean the same thing in this context (looking at the current lead-screw, it does look it has 8 'starts', but that seems to be cancelled out by how the nut is made so the travel distance for 1 rotation is indeed 25mm).

Check out the link I provided to the products' page on Igus and see what it says there, or if you prefer, here's a snapshot of the 2 relevant rows in the listing:

One thing that still puzzles me is that the above calculations all seem to use 16, rather than 256, for the micro-stepping value - can anyone explain this please?

Also, assuming @fcwilt is correct (which looks to be the case - thanks, @fcwilt!), any thoughts on the potential increase of resolution (from 256 to 533 steps/mm vs losing the round numbers for steps and having slower movement overall?

Hi,

This subject always get my brain in a twist so I thought I'd ask for some help

My steppers are 0.9 degrees (400 steps per revolution).

I currently have these high-helix lead-screws from Igus installed: DST-LS-10x25-R-ES, which have the following specs:

Diameter: 10mm
Pitch: 25mm
No. of threads: 8

With micro-stepping set to 256 (x16 with interpolation), this comes down to 256 steps per mm (I know it's right cause it works in reality, but I completely forgot how I got to this value).

Now I'm considering going with similar lead-screws but with shorter pitch (yet also less threads), in the hope of increasing the resolution.

The intended lead-screws are also from Igus: DST-LS-10x12-R-ES, and they have the following specs:

Diameter: 10mm
Pitch: 12mm
No. of threads: 4

Could someone please help me calculate how many steps per mm would this lead-screw yield? and, for my education, how the calculation is done?

Btw, I'd like to keep the 10mm diameter as my lead-screw nuts and the bearings are all for that size and I'd rather change only the lead screws themselves if I can.

Many thanks in advance,
SnowCrash

Thanks @aidar!

Hi,

I was previously told on the forum that putting the following line in config.g would allow me to move the effector without homing:

M564 H0

However, this doesn't seem to work as I'm getting the following error message:

I've tried putting the above line in config.g and re-starting the Duet, as well as running the command from the command line. No luck.

I've also tried switching between relative and absolute position (G90/G91) prior to running the command, but no joy either.

config.g & config-override.g files are attached below.

Also, here's my system diagnostics if it helps:

1:36:38 PMM122
=== Diagnostics ===
Used output buffers: 3 of 32 (12 max)
=== Platform ===
RepRapFirmware for Duet 2 WiFi/Ethernet version 1.21 running on Duet WiFi 1.02 or later
Board ID: 08DGM-956GU-DJMSN-6J1DL-3S86P-T9RZG
Static ram used: 16152
Dynamic ram used: 100560
Recycled dynamic ram: 2072
Stack ram used: 1224 current, 4408 maximum
Never used ram: 7880
Last reset 00:07:26 ago, cause: software
Last software reset at 2018-12-12 13:29, reason: User, spinning module GCodes, available RAM 7816 bytes (slot 2)
Software reset code 0x0003 HFSR 0x00000000, CFSR 0x00000000, ICSR 0x0441f000, BFAR 0xe000ed38, SP 0xffffffff
Error status: 0
Free file entries: 10
SD card 0 detected, interface speed: 20.0MBytes/sec
SD card longest block write time: 80.6ms
MCU temperature: min 22.9, current 27.0, max 27.5
Supply voltage: min 1.5, current 24.1, max 24.3, under voltage events: 2, over voltage events: 0
Driver 0: standstill, SG min/max not available
Driver 1: standstill, SG min/max not available
Driver 2: standstill, SG min/max not available
Driver 3: standstill, SG min/max not available
Driver 4: standstill, SG min/max not available
Date/time: 2018-12-12 13:36:37
Slowest main loop (seconds): 0.091238; fastest: 0.000044
=== Move ===
MaxReps: 0, StepErrors: 0, LaErrors: 0, FreeDm: 240, MinFreeDm 240, MaxWait: 0ms, Underruns: 0, 0
Scheduled moves: 0, completed moves: 0
Bed compensation in use: none
Bed probe heights: 0.000 0.000 0.000 0.000 0.000
=== Heat ===
Bed heaters = -1 -1 -1 -1, chamberHeaters = -1 -1
=== GCodes ===
Segments left: 0
Stack records: 2 allocated, 0 in use
Movement lock held by null
http is idle in state(s) 0
telnet is idle in state(s) 0
file is idle in state(s) 0
serial is idle in state(s) 0
aux is idle in state(s) 0
daemon is idle in state(s) 0
queue is idle in state(s) 0
autopause is idle in state(s) 0
Code queue is empty.
=== Network ===
Responder states: HTTP(1) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0) Telnet(0)
HTTP sessions: 1 of 8

• WiFi -
  Network state is running
  WiFi module is connected to access point
  Failed messages: pending 0, notready 0, noresp 0
  WiFi firmware version 1.21RC4(08b3)
  WiFi MAC address 5c:cf:7f:76:71:d8
  WiFi Vcc 3.30, reset reason Turned on by main processor
  WiFi flash size 4194304, free heap 16856
  WiFi IP address 192.168.1.110
  WiFi signal strength -64dBm, reconnections 0, sleep mode modem
  Socket states: 2 0 0 0 0 0 0 0
  === Filament sensors ===
  Extruder 0 sensor: no filament
  === Expansion ===

I really need to be able to move the effector without homing first - how do I get this done?

Many thanks in advance,
SnowCrash

0_1544622106203_config.g
0_1544622120876_config-override.g

Hi @Cocopufft,

If you're looking for steppers with a detachable connector (JST-style), I have an option for you to consider.

I got 6 x Nema-17 Steppers (48cm long) from a specialized company in Singapore called WantaiMotor.

Their customer service was excellent & the construction of the steppers themselves looks very solid to me. I had them custom made for my needs (2 flat sides on a 25mm long shaft), so they took about a month to be made, but you can have them with a regular round shaft if you like so they may have a shorter lead time. I also had them made with a JST connector instead of the permanent wires.

Other specs can also be requested, you just need to discuss them with their customer service directly (I wanted very low inductance and resistance with relatively high max current).

The price was very reasonable too: about £6-7 per stepper as best I can remember (excluding shipping).

Here are the specs to compare with other alternatives:

Max Current: 2.4A

Angle: 0.9 (400 steps/revolution)

Inductance: 1.8mH/Phase

Resistance: 0.9R

Holding Torque: 42Ncm

I haven't had long to work with these steppers since I received them and only had a chance to test that they're working properly which they do. However, I should note that when attached to the Duet they are currently quite noisy on idle though I think this has to do with needing to tweak the settings which I haven't had time to do yet (can't be certain though).

Hope this helps.
SnowCrash

@crazyjane, to the best of my knowledge, one important point to bear in mind in this context is that the 3rd party board needs to have a 400R reference resistor for the board to work properly (i.e. give correct readings) when hooked up to the Duet.

Based on the schematics, 400R is the value of the reference resistor on the Duet's daughter board (although in some cases it's noted as 430R - don't ask me why), and, again as far as I know, that's the value used by the Duet's firmware (unless there's a way of tweaking this value in the settings - I haven't looked into that).

For my machine, I've actually made my own custom little daughter board for the PT-100 based on the MAX31865 & a 400R reference resistor (I didn't want to use the Duet's as I didn't want the daughter board to sit on top of the controller), and it works great

Hope it helps.
SnowCrash

edit: for anyone reading this, as @dc42 helpfully noted below, the reference resistor's value can indeed be set in config.g, so please disregard my comment above about needing to use a 400R reference resistor. Instead, just remember to tweak that value in the settings.

I understand what you're saying, @jml, and you might be right. Can't say for sure. Seems to me that this setup gives just a bit of play which is better than rigid coupling, but perhaps not much. Plus I think the jaw coupling are better at reducing backlash, but again, perhaps it's just wishful thinking. Anyway, if anyone has a better solution I'd be happy to learn what it is

It's worth noting that the bottom bearing (ie the one mounted on the stepper's shaft), is meant to protect the inner bearings inside the motor. I believe that together with the bottom part of the jaw coupling is does a better job at this than rigid couplings, but again, it's just something that seems logical to me, not something I can prove to be correct.

As for the bearings, I'm using these bearings from Igus.

Hi @jml,

I have high quality jaw couplings from Misumi and they'll separate if enough pressure is applied.

My solution is to place 2 sleeve bearings very close to the coupling: one sleeve bearing on the steppers' shaft below the coupling, and the other on the lead-screw above the coupling, thus 'sandwiching' the coupling in between (but without actually putting any pressure on the coupling - just close enough to prevent it from separating).

Here are a couple of pics to illustrate what I mean (in the second pic, everything has been stripped away except the coupling and 2 sleeve bearings to make it easier to see how they're placed in relation to one another):

Hope this helps.
SnowCrash

Hi @totalitarian,

Just thought I'd chime in and note that to the best of my knowledge the power control of the fan connectors on the Duet is done by toggling the ground pins rather than the VCC pins.

So assuming you are indeed measuring the 2 pins on the connector itself (VCC & GND) - and not taking GND from somewhere else when measuring the voltage on the VCC pin - then it sounds to me that @Phaedrux's guess about a shorted fan header is the most likely explanation (it would also explain why the previous fan failed).

To check if there's a short or not in the fan header, completely disconnect the board from the power supply and switch your multimeter to measuring the minimal amount of resistance it can. Then touch the 2 fan connector pins with the 2 multimeter probes. The reading ought to be '1' meaning 'open circuit' . On the other hand, if you get any positive value when reading the resistance, then there's a short.

To test the fan itself, you can connect it to a separate power supply with the correct voltage. Alternatively, you can also connect it to one of the two 'always on' fan connectors on the Duet and see if it runs as expected.

Hope this helps.

Thanks for the confirmation, @dc42! But what's the calculation behind it?

@gnydick said in Rigid vs Flexible Couplers for Trapezoidal Leadscrews?:

I have a novel approach. I use rigid couplers, but I use a solid petg plate to attach the brass lead nut. It's 1-2mm thick. The plate doesn't move, but it can flex a little, so the lead screw doesn't bind if you get a little wobble. The plate sits atop The bed frame which has a large hole cut and the petg plate is like a patch over the hole. The nut is under the bed, screwed up into the plate that sits on top of the bed.

I also use VHB gel tape to mount the motors to the floor of my enclosure. I can fine tune the position and gel works amazing well.

Pics please?