Posts made by Visionary

@mrehorstdmd

The backlash in my case may have come from linear rails combined with a ball screw and a stepper motor. Stepper motors can't quite perfectly instantly reach and stay at commanded position. The torque is very low when stepper motor rotor is very close to position it is suppose to be and this causes some springiness, which shows as backlash. The particular linear rails that I used when I tested this were quite stiff and not very smooth, which caused more load on the system making the backlash more pronounced. This kind of backlash isn't big problem and doesn't show on prints because normally you are only going one way on Z-axis during printing. However, this could cause problems for Z-hopping and nonplanar printing.

I can't remember the exact backlash but I think it was around 0.01-0.03MM (using SFU1605 + Stepper + disc shaft coupling).

Also I had my endstops at max end and therefore I had to home to max on Z-axis, which took maybe like 20 seconds to do due to low speeds. My Z-motors would stall if I went any faster.

@dc42

Peopoly uses one linear motor on each X and Y axis and two linear rail blocks on each Y-axis rail. On their printer it seems to work even though there is some cantilever pulling/pushing going on. Thomas Sanladerer shows some details on the printer on his review video.

STōN-WoLF printer also has kinematic configuration that could be a bit more suitable for linear motors.

I've had (Chinese) ball screws on my Z-axes and they are ok, but they still have slight Z-wobble and they do have noticeable amount of backlash. Using linear motors also on Z-axis would definitely be expensive, but I'm curious if there would be better in every other way (speed, noise, precision, no moving parts, no grease). Preventing bed from dropping hard when unpowered is an issue too.

Many of the examples of DIY linear motors on YT and on Internet use 3-phase setup and drive the motor with VFD or what I assume is a BLDC drive. If it would be possible to use 2-phase setup instead and use directly say 6HC stepper drivers then that would very simple if possible. Or could ODrive Pro-board be used through CAN-connection to Duet to drive a 3-phase linear motor? I do realise that this would be expensive, but e.g. one Clearpath servo imported to Europe costs >400€ and that doesn't even include belt drive components.

@dc42

If it was built as a 2-phase motor, there is a possibility that our upcoming closed loop stepper motor driver could drive it, depending on how much power it needed.

Is it possible to drive DIY 2-phase closed loop linear motor with (new) Duet hardware directly (or with additional hardware)? Btw I'm not so sure that you can get enough force from a linear motor without using strong magnets instead of steel bar and a copper sheet. Some example demo videos on Youtube make such a linear motor seem quite weak.

@o_lampe

BLDC motors referred by simpleFOC cost more than NEMA 23s or have less power. Can you refer a BLDC motor with sensor that is similarly priced as NEMA 23s and have torque of 2-3 Nm at 300 RPM?

But would slave motors rotate at different if there is no load on them?

I think I'm going to try stuff in following order:

1. Simple signal converter between external cheap driver and signal source. For testing only.
2. Arduino or Duet (these for sure have better features). For testing only.
3. Custom driver boards (this would only be in final version and it's a bit early to think about that).

Getting to the actual testing phase probably takes a lot of time.

@Maestro said in Analog current -> duet -> stepper motor speed:

I think he was thinking that the output from the frequency transducer could be used to directly drive the pulse/step input for an external driver.

That is what I meant. So is this kind of setup possible:

The setup above would be for one time testing the motion. Some other control solution (and components) would probably be much better alternatives. I just need something that works with existing software (which I cannot change) used by rest of the machine.

Frequency limits might be problem, though I think it should be smooth enough for simple test. Jerk and acceleration control would be done by software of the input mA signal.

@dc42 said in Analog current -> duet -> stepper motor speed:

It occurs to me that this may meet your requirement for continuous motion at a selectable speed.

The rollers are constantly moving, but they change rotation directions periodically and do high movement speeds occasionally. Having constant torque is not needed as long the movement stays relatively smooth and requested speeds are followed.

########################################################

I think this could be suitable converter that can directly control an external stepper driver speed: MINI MCR-SL-UI-F.

@T3P3Tony

In the first version RPM of one motor is measured from its shaft and it is used to control all of the motors. The measurement shouldn't be required and it should work just fine without it if motors are chosen correctly and no step losses occur even at max loads. All of the loads in my application are predictable.

I've been trying to google suitable converters. Would any converter do if it outputs pulse at desired frequencies? Does the pulse shape matter?

What I mean by custom drivers is that using something like Duet as final solution to drive the rollers is overkill, but I need 5-8 drivers in a single package (PCB board?) and many of the existing solutions I've found so far seem very expensive or they lack sufficient power. Would it make sense to design custom PCB with 5-8 drivers with 4-5 Amps (perhaps even with signal converter integrated) that has input of 4-20mA for speed and digital input for direction? So no encoder in this type of setup and the production volume would be potentially hundreds yearly.

Current system:
Inputs to stepper drivers/converters:

• 4-20mA speed signal
• digital signal of rotation direction (I don't know yet what voltage)

Output information from motor shaft

• Encoder (I don't know anything about the sensor spefically, but it should not matter if there are plans to get rid of it anyways eventually)

@o_lampe

BLDC motors have low torque at low speeds. In my application stepper motors (vs. for example servos and BLDC motors) have high enough torque at about 0-300 RPM to be used without gearboxes. SimpleFOC seems interesting and I will look into it. Plug and play options would be preferable for the converter. The converter may need to be able to adjust its output to determine speeds (something like this: 4mA -> 0 RPM, 16 mA -> 300 RPM).

@T3P3Tony
@Maestro

Thanks for the responses.

The application is to run 10 rollers that move sheets of materials. In the application driving the rollers do not need to be in real time. Each motor rotates two rollers via timing belt. The accuracy does not need to be as high as in CNC applications (but it still needs to be quite good), but the system needs to be repeatable, smooth and the sheet materials have to maintain predictable position when oscillating several times. The materials and the rollers are heavy and this could be a problem for the drivers when decelerating (duet drivers or external drivers). The roller drive is just for testing proof of concept and probably more refined solution would be used in the end.

I intend to use Nema 23/24 with up to 4A current. Drivers that can do that are a bit hard to find. Duet can run predetermined G-code precisely and has high current drivers. I think it may be possible that simple signal conversion to step direction and pulse may not be accurate enough or has some other issues. Use of the 4-20mA signal would be however convenient as it is compatible with existing software/automation systems. For those reasons I think Duet could be good for my use case as I can test the setup either with external 4-20mA signal + converter + Duet or Duet in standalone mode.

I also found that there are integrated drivers that can be mounted directly onto the motors and they could one solution. If I can prove the concept, could custom driver boards (possibly with signal converters) be a good cost effective solution?

Is it possible to use 4-20mA signal to control speeds of stepper motors connected to Duet 6HC (and expansion boards)? The direction would be determined by digital input. All connected motors would spin at the same rate or if possible at predetermined ratios to one another.

This thread might be redundant if there is already another, although I couldn't find one.

@droftarts

I get:

HTTP is enabled on port 80
FTP is disabled
TELNET is disabled

Is it possible that the servo is broken?
Can incorrect wiring to right pins cause damage to Duet or the servos?
The servos that I have can rotate by hand more than they can by when they are controlled electronically. Do they have to be in certain starting position to work?

M122

M122
=== Diagnostics ===
RepRapFirmware for Duet 3 MB6HC version 3.4.5 (2022-11-30 19:35:23) running on Duet 3 MB6HC v1.01 (standalone mode)
Board ID: 08DJM-956BA-NA3TJ-6J9D2-3S06T-9V8GT
Used output buffers: 3 of 40 (14 max)
=== RTOS ===
Static ram: 152760
Dynamic ram: 98776 of which 400 recycled
Never used RAM 98736, free system stack 206 words
Tasks: NETWORK(ready,35.1%,252) ETHERNET(notifyWait,0.2%,561) ACCEL(notifyWait,0.0%,348) HEAT(notifyWait,0.0%,322) Move(notifyWait,0.0%,351) CanReceiv(notifyWait,0.0%,944) CanSender(notifyWait,0.0%,336) CanClock(delaying,0.0%,333) TMC(notifyWait,7.8%,91) MAIN(running,56.6%,925) IDLE(ready,0.2%,30), total 100.0%
Owned mutexes:
=== Platform ===
Last reset 00:00:55 ago, cause: power up
Last software reset at 2023-01-02 16:44, reason: User, GCodes spinning, available RAM 98736, slot 1
Software reset code 0x0003 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x00400000 BFAR 0x00000000 SP 0x00000000 Task MAIN Freestk 0 n/a
Error status: 0x00
Aux0 errors 0,0,0
Step timer max interval 127
MCU temperature: min 28.9, current 39.7, max 39.9
Supply voltage: min 24.3, current 24.4, max 24.4, under voltage events: 0, over voltage events: 0, power good: yes
12V rail voltage: min 12.1, current 12.1, max 12.2, under voltage events: 0
Heap OK, handles allocated/used 0/0, heap memory allocated/used/recyclable 0/0/0, gc cycles 0
Events: 0 queued, 0 completed
Driver 0: standstill, SG min 0, mspos 8, reads 46633, writes 14 timeouts 0
Driver 1: standstill, SG min 0, mspos 8, reads 46633, writes 14 timeouts 0
Driver 2: standstill, SG min 0, mspos 8, reads 46634, writes 14 timeouts 0
Driver 3: standstill, SG min 0, mspos 8, reads 46634, writes 14 timeouts 0
Driver 4: standstill, SG min 0, mspos 8, reads 46634, writes 14 timeouts 0
Driver 5: standstill, SG min 0, mspos 8, reads 46634, writes 14 timeouts 0
Date/time: 2023-01-03 11:35:39
Slowest loop: 4.43ms; fastest: 0.05ms
=== Storage ===
Free file entries: 10
SD card 0 detected, interface speed: 25.0MBytes/sec
SD card longest read time 2.4ms, write time 0.0ms, max retries 0
=== Move ===
DMs created 125, segments created 0, maxWait 0ms, bed compensation in use: none, comp offset 0.000
=== MainDDARing ===
Scheduled moves 0, completed 0, hiccups 0, stepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== AuxDDARing ===
Scheduled moves 0, completed 0, hiccups 0, stepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== Heat ===
Bed heaters 0 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1, chamber heaters -1 -1 -1 -1, ordering errs 0
=== GCodes ===
Segments left: 0
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
USB is idle in state(s) 0
Aux is idle in state(s) 0
Trigger is idle in state(s) 0
Queue is idle in state(s) 0
LCD is idle in state(s) 0
SBC is idle in state(s) 0
Daemon is idle in state(s) 0
Aux2 is idle in state(s) 0
Autopause is idle in state(s) 0
Code queue is empty
=== CAN ===
Messages queued 500, received 0, lost 0, boc 0
Longest wait 0ms for reply type 0, peak Tx sync delay 0, free buffers 50 (min 50), ts 279/0/0
Tx timeouts 0,0,278,0,0,220 last cancelled message type 30 dest 127
=== Network ===
Slowest loop: 4.33ms; fastest: 0.03ms
Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0) Telnet(0)
HTTP sessions: 1 of 8
= Ethernet =
State: active
Error counts: 0 0 0 1 0 0
Socket states: 5 2 2 2 2 0 0 0
=== Multicast handler ===
Responder is inactive, messages received 0, responses 0

@achrn said in Hobbyservo controlled part cooling fan (compressor+valve):

I agree with that colour scheme and wiring layout. As previously, I would expect the DC-DC converter to have the 0V in and 0V out connected together internally (if you have a multimeter you could check there's no voltage across them, but I doubt this is the problem).

Tested the difference in voltage and it was 0V.

• try some different S values in M280 (as @droftarts suggests)
• I see the fan is now commented out of the config file, but is anything still physically connected on OUT9? (I don't think it will matter actually, but worth a try disconnecting it if it is?)
• try connecting the orange wire to io7.out and changing the config line to M950 S1 C"io7.out" and M280 P1 S<whatever> (this is just in case something is up with your out9 on the board, from config it doesn't look like you're using io7 yet)

Switching S value didn't work (that were on the product page of the servo), but I might keep trying other values anyways. Nothing is connected to out9 (fan) pin. I changed to io7.out in config and rewired the servo and it behaves the same as before.

Btw how do you differentiate between fan pin out9 and 5V PWM pin out9 in config?
The green arrow points to the pin I've been using as out9.

@droftarts said in Hobbyservo controlled part cooling fan (compressor+valve):

@Visionary try

M98 P”/sys/config.g”

This didn't work either, got the same error.

Almost all servos accept a pulse width range of at least 1us to 2us, which corresponds to an S parameter range of 44.2 to 141.2 degrees. So for many servos, values in the range 44.2 to 141.2 or alternatively 1000 to 2000 will cover the full operating range of the servo.

I didn't realize to check allowed servo angles. I thought they all started at 0 Degrees.
I checked the correct allowed pulse widths for both servos.
I changed to using microseconds in the command, but that didn't work and I got the same result.

@droftarts said in Hobbyservo controlled part cooling fan (compressor+valve):

@Visionary also, send

M98 P”config.g”

And see if reports any errors.

Ian

This gives message : "Warning: Macro file ”config.g” not found"

@achrn

I switched to attempting to get working the smaller (MS-1.3-9) servo.
I've connected it following way on 6HC:

• Orange wire || Out9 (5V PWM)
• Red wire || +5V (external DC-DC converter)
• Brown wire || GND (external DC-DC converter, which is not directly connected atm to main 24V PSU GND)

I've also noticed that at start up the servo moves (after I removed fan assigments), but I still can't move it with G-code commands like M280 P5 S50. Instead the servo makes noise that indicates its trying to hold its position. The servo also makes random twiches and overheats the servo.

Note that I tried to switch number of the (P1) servo to different one (P5).

Current config:

; Configuration file for Duet 3 MB 6HC (firmware version 3.3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.3.15 on Tue Dec 20 2022 09:34:36 GMT+0200 (Itä-Euroopan normaaliaika)

; General preferences
M575 P1 S1 B57600                            ; enable support for PanelDue
G90                                          ; send absolute coordinates...
M83                                          ; ...but relative extruder moves
M550 P"My Printer"                           ; set printer name
M669 K1                                      ; select CoreXY mode

; Network
M551 P""                                ; set password. This is redacted.
M552 P0.0.0.0 S1                             ; enable network and acquire dynamic address via DHCP
M586 P0 S1                                   ; enable HTTP
M586 P1 S0                                   ; disable FTP
M586 P2 S0                                   ; disable Telnet

; Drives
M569 P0.0 S0                                 ; physical drive 0.0 goes
M569 P0.1 S0                                 ; physical drive 0.1 goes 
M569 P0.2 S0                                 	; Z1 motor (Left from user on printer)
M569 P0.3 S1									; Z2 motor (back motor)
M569 P0.4 S0									; Z3 motor (right from user on printer)
M569 P0.5 S1                                 ; physical drive 0.5 goes forwards
M584 X0.1 Y0.0 Z0.2:0.3:0.4 E0.5                     ; set drive mapping
M350 X16 Y16 Z16 E16 I1                      ; configure microstepping with interpolation
M92 X80.00 Y80.00 Z640.00 E420.00            ; set steps per mm
M566 X700.00 Y700.00 Z60.00 E120.00          ; set maximum instantaneous speed changes (mm/min)
M203 X9000.00 Y9000.00 Z600.00 E1800.00      ; set maximum speeds (mm/min)
M201 X1800.00 Y1800.00 Z30.00 E250.00          ; set accelerations (mm/s^2)
M906 X1000 Y1000 Z1200:2600:1200 E800 I30               ; set motor currents (mA) and motor idle factor in per cent
M84 S30                                      ; Set idle timeout

; Axis Limits
M208 X-25.8 Y-10 Z0 S1                             ; set axis minima
M208 X400 Y400 Z490 S0                       ; set axis maxima

; Endstops
M574 X1 S1 P"io1.in"                        ; low end
M574 Y1 S1 P"io2.in"                        ; low end
M574 Z2 S1 P"io3.in+io4.in+io5.in"                        ; Z1, Z2, Z3 High end, Three ball scews


M671 X-80.0:200.0:480.0 Y400.0:-40.0:400.0 ; Z leadscrews are at (-80,400), (200,-40) and (480,400)


; Z-Probe
M558 P0 H5 F120 T6000                        ; disable Z probe but set dive height, probe speed and travel speed
M557 X50:350 Y50:350 S300                     ; define mesh grid

; Heaters
; BED
M308 S0 P"temp1" Y"thermistor" T100000 B3974 ; configure sensor 0 as thermistor on pin temp1
M950 H0 C"out3" T0                           ; create bed heater output on out3 and map it to sensor 0
M307 H0 B1 R0.25 S1.00                             ; enable bang-bang mode for the bed heater and set PWM limit
M140 H0                                      ; map heated bed to heater 0
M143 H0 S120                                 ; set temperature limit for heater 0 to 120C
; HOTEND
M308 S1 P"temp0" Y"pt1000" 
;M308 S1 P"temp0" Y"thermistor" T100000 B4725 C7.06e-8 ; configure sensor 1 as thermistor on pin temp0
M950 H1 C"out1" T1                           ; create nozzle heater output on out1 and map it to sensor 1
M307 H1 B0 S1.00                             ; disable bang-bang mode for heater  and set PWM limit
M143 H1 S320                                 ; set temperature limit for heater 1 to 320C

; Fans
;M950 F0 C"out9" Q500                         ; create fan 0 on pin out9 and set its frequency
;M106 P0 S0 H-1                               ; set fan 0 value. Thermostatic control is turned off
;M950 F1 C"out8" Q500                         ; create fan 1 on pin out8 and set its frequency
;M106 P1 S1 H-1                               ; set fan 1 value. Thermostatic control is turned off

; Tools
M563 P0 D0 H1 F0                             ; define tool 0
G10 P0 X0 Y0 Z0                              ; set tool 0 axis offsets
G10 P0 R0 S0                                 ; set initial tool 0 active and standby temperatures to 0C

;Accelerometer
M955 P0 I56 C"spi.cs3+spi.cs2"	

; Servo for compressor fan valve
M950 S5 C"out9" 	; assign GPIO port 1 to out9 (Servo header), servo mode
M280 P5 S30			; Move servo with

; Compressor 
M950 P2 C"out2" Q0								 ; Compressor ON/OFF SSR

@achrn

I initially copied code for the servo from documentation and the comment is from there. The servo is connected to correct pin on the board. I tested another servo (ms-1.3-9) and it didn't work either. I'm assuming that with servo (MS-1.3-9) brown is negative, Red is positive and orange is PWM. Both servos should be able to handle 5V PWM.

I then switched to using 5V PWM pin "out9" on 6HC and that didnt work either.

The commands I'm sending to test the servo are:

• M280 P1 S0
• M280 P1 S35

@o_lampe

The converter can supply 5A and is rated at 25W. From what I read on documentation Duet ports probably cannot supply enough amps safely to this large servo.

@achrn
I still can't get it to work. btw what I meant by 5V PSU it is actually DC-DC converter.

@o_lampe
I have seperate 5V PSU (DC-DC converter). Does it have to be connected to negative of Duet? If so can I use power in negative on 6HC board?

@OwenD said in Hobbyservo controlled part cooling fan (compressor+valve):

@Visionary said in Hobbyservo controlled part cooling fan (compressor+valve):

M950 S1 C"out7" ; assign GPIO port 1 to out9 (Servo header), servo mode
M280 P0 S80 ; Move servo with

Try

M950 S1 C"out7" 	; assign GPIO port 1 to out9 (Servo header), servo mode
M280 P1 S80		; Move servo with

I tried this, but it didn't work

@jay_s_uk

But wouldn't the motors lose position during switch in axis configuration? Just realized that physical adjustable endstops could do what wanted but those can be difficult to make work well.