Blinking bed heater LED, no heat



  • The title says it all.


  • administrators

    @1d1 said in Blinking bed heater LED, no heat:

    The title says it all.

    ..except which Duet you are using, which firmware version, and how the bed heater is connected to the Duet.



  • Duet 2, RRF3.1.1, via DC-DC SSR connected through the PS. I have used this setup for several years and recently overhauled the printer with a new Duet (maybe 6 ms. old) and a whole new heated bed original to the Tevo Black Widow. The bed was soldered incorrectly at the connector with the thermistor leads in the wrong location. I switched around the connector leads to the Duet and everything was working well. However, the heater LED on the board started blinking fairly rapidly two days ago and goes into a fault mode when simultaneously heating the hot end. I think the blinking is when it reaches temp and is maintaining it at that level, Then faults to off when adding the extra load from the hot end. So - maybe an overloaded/tired PS? It is a 5 y.o. Meanwell 600...


  • Moderator

    Do you get a heater fault message?
    What wattage is the bed and hotend heater?



  • 40w hot end (new Maxiwatt 24v) and not sure on bed. However, this is a combo I've been using for a long time and the Meanwell 600 is overkill generally. I'll try to get the bed info.
    Yes, I get a fault message about the 15 degree disparity when the bed stops heating and cools below target temp.
    Bed = 250w


  • Moderator

    For the sake of completeness can you post your config.g and the results of M122 and M98 P"config.g"?

    Have you PID tuned the bed?

    Does the PSU output voltage drop at all under load?

    Are the bed heater screw terminals tight?



  • @Phaedrux said in Blinking bed heater LED, no heat:

    M98 P"config.g"

    M98 P"config.g"
    HTTP is enabled on port 80
    FTP is disabled
    TELNET is disabled
    Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 365C
    Warning: Heater 1 appears to be over-powered. If left on at full power, its temperature is predicted to reach 852C
    
    	M122
    === Diagnostics ===
    RepRapFirmware for Duet 2 WiFi/Ethernet version 3.1.1 running on Duet WiFi 1.02 or later
    Board ID: 08DGM-9T6BU-FG3SJ-6J1FA-3S46Q-1VWHD
    Used output buffers: 3 of 24 (21 max)
    === RTOS ===
    Static ram: 27980
    Dynamic ram: 93904 of which 100 recycled
    Exception stack ram used: 264
    Never used ram: 8824
    Tasks: NETWORK(ready,368) HEAT(blocked,1224) MAIN(running,1824) IDLE(ready,80)
    Owned mutexes: WiFi(NETWORK)
    === Platform ===
    Last reset 00:02:13 ago, cause: power up
    Last software reset at 2020-10-26 17:37, reason: User, spinning module GCodes, available RAM 8692 bytes (slot 0)
    Software reset code 0x0003 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x0441f000 BFAR 0xe000ed38 SP 0xffffffff Task MAIN
    Error status: 0
    MCU temperature: min 15.4, current 21.2, max 21.3
    Supply voltage: min 23.9, current 24.1, max 24.4, under voltage events: 0, over voltage events: 0, power good: yes
    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: 2020-10-30 15:28:43
    Cache data hit count 231726101
    Slowest loop: 28.97ms; fastest: 0.12ms
    I2C nak errors 0, send timeouts 0, receive timeouts 0, finishTimeouts 0, resets 0
    === Storage ===
    Free file entries: 10
    SD card 0 detected, interface speed: 20.0MBytes/sec
    SD card longest read time 3.7ms, write time 21.3ms, max retries 0
    === Move ===
    Hiccups: 0(0), FreeDm: 169, MinFreeDm: 169, MaxWait: 0ms
    Bed compensation in use: none, comp offset 0.000
    === MainDDARing ===
    Scheduled moves: 0, completed moves: 0, StepErrors: 0, LaErrors: 0, Underruns: 0, 0  CDDA state: -1
    === AuxDDARing ===
    Scheduled moves: 0, completed moves: 0, StepErrors: 0, LaErrors: 0, Underruns: 0, 0  CDDA state: -1
    === Heat ===
    Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1 -1 -1
    Heater 1 is on, I-accum = 0.0
    === 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
    Daemon is idle in state(s) 0
    Autopause is idle in state(s) 0
    Code queue is empty.
    === Network ===
    Slowest loop: 32.39ms; fastest: 0.00ms
    Responder states: HTTP(2) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0), 0 sessions
    HTTP sessions: 1 of 8
    - WiFi -
    Network state is active
    WiFi module is connected to access point 
    Failed messages: pending 0, notready 0, noresp 0
    WiFi firmware version 1.23
    WiFi MAC address ec:fa:bc:25:34:b1
    WiFi Vcc 3.38, reset reason Unknown
    WiFi flash size 4194304, free heap 21456
    WiFi IP address 192.168.1.194
    WiFi signal strength -54dBm, reconnections 0, sleep mode modem
    Socket states: 0 0 0 0 0 0 0 0
    
    0:/sys/config.g
    ; Configuration file for Duet WiFi (firmware version 3)
    ; executed by the firmware on start-up
    ;
    ; generated by RepRapFirmware Configuration Tool v3.1.4 on Mon Oct 26 2020 14:50:36 GMT-0600 (Central Standard Time)
    
    ; General preferences
    G90                                                ; send absolute coordinates...
    M83                                                ; ...but relative extruder moves
    M550 P"BW Newest"                                  ; set printer name
    
    ; Network
    M552 S1                                            ; enable network
    M586 P0 S1                                         ; enable HTTP
    M586 P1 S0                                         ; disable FTP
    M586 P2 S0                                         ; disable Telnet
    
    ; Drives
    M569 P0 S1                                         ; physical drive 0 goes forwards
    M569 P1 S1                                         ; physical drive 1 goes forwards
    M569 P2 S1                                         ; physical drive 2 goes forwards
    M569 P3 S1                                         ; physical drive 3 goes forwards
    M584 X0 Y1 Z2 E4                                   ; set drive mapping
    M350 X16 Y16 Z16 E16 I1                            ; configure microstepping with interpolation
    M92 X80.00 Y80.00 Z400.00 E1675.00                 ; set steps per mm
    M566 X900.00 Y900.00 Z60.00 E1800.00               ; set maximum instantaneous speed changes (mm/min)
    M203 X720000.00 Y720000.00 Z600.00 E3600.00        ; set maximum speeds (mm/min)
    M201 X1000.00 Y1000.00 Z1000.00 E2000.00           ; set accelerations (mm/s^2)
    M906 X800 Y800 Z800 E400 I30                       ; set motor currents (mA) and motor idle factor in per cent
    M84 S30                                            ; Set idle timeout
    
    ; Axis Limits
    M208 X0 Y0 Z0 S1                                   ; set axis minima
    M208 X320 Y205 Z310 S0                             ; set axis maxima
    
    ; Endstops
    M574 X1 S1 P"xstop"                                ; configure active-high endstop for low end on X via pin xstop
    M574 Y1 S1 P"ystop"                                ; configure active-high endstop for low end on Y via pin ystop
    M574 Z1 S1 P"zstop"                                ; configure active-high endstop for low end on Z via pin zstop
    
    ; Z-Probe
    M558 P0 H5 F120 T6000                              ; disable Z probe but set dive height, probe speed and travel speed
    M557 X15:215 Y15:195 S20                           ; define mesh grid
    
    ; Heaters
    M308 S0 P"bedtemp" Y"thermistor" T100000 B4036     ; configure sensor 0 as thermistor on pin bedtemp
    M950 H0 C"bedheat" T0                              ; create bed heater output on bedheat and map it to sensor 0
    M307 H0 B0 S1.00                                   ; disable 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
    M308 S1 P"e0temp" Y"thermistor" T100000 B4036      ; configure sensor 1 as thermistor on pin e0temp
    M950 H1 C"e0heat" T1                               ; create nozzle heater output on e0heat and map it to sensor 1
    M307 H1 B0 S1.00                                   ; disable bang-bang mode for heater  and set PWM limit
    
    ; Fans
    M950 F0 C"fan0" Q500                               ; create fan 0 on pin fan0 and set its frequency
    M106 P0 S0 H-1                                     ; set fan 0 value. Thermostatic control is turned off
    M950 F1 C"fan1" Q500                               ; create fan 1 on pin fan1 and set its frequency
    M106 P1 S1 H1 T45                                  ; set fan 1 value. Thermostatic control is turned on
    
    ; Tools
    M563 P0 S"Extruder" 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
    
    ; Custom settings are not defined
    
    ; Miscellaneous
    M501                                               ; load saved parameters from non-volatile memory
    M911 S10 R11 P"M913 X0 Y0 G91 M83 G1 Z3 E-5 F1000" ; set voltage thresholds and actions to run on power loss
    T0                                                 ; select first tool
    

    I have not PID tuned the bed since replacing it. The PSU terminals are all tight. The bed connector is factory new (except where I changed terminals for the thermistor). In this moment of checking everything again, it is all working properly. The lowest voltage drop when all things are on simultaneously is 23.6 but it is a momentary drop and usually varies between 23.7 and 24.1
    That's a lot of information! Thanks for your efforts! Dean


  • Moderator

    Thanks. Everything looks in order.

    I would suggest PID tuning the bed again starting at room temp and saving the results with M500.

    Hopefully it's just a fluke.



  • While writing the above, the heater faulted again:

    rror: Heater 0 fault: temperature excursion exceeded 15.0°C (target 80.0°C, actual 64.6°C)
    


  • Thanks, @Phaedrux - I try the PID tune....


  • Moderator

    Can you post a screen shot of your temperature graph?>


  • Moderator

    @1d1 said in Blinking bed heater LED, no heat:

    The bed connector is factory new (except where I changed terminals for the thermistor).

    Is it possible the thermistor is losing physical connection to the heater? Or a wiring fault? Failing thermistor?



  • The thermistor readings remain consistent. Trying to heat the hot end to 250 and the bed to 80, it reaches the target temp and gradually loses temperature until it faults - as if it can't somehow maintain that level. The temperature graph is steady and solid, reflecting exactly what is happening. Could it be the SSR is failing? The wiring all looks good and it has worked solidly for appx. 5 years. It has to be either the bed or SSR I think. And as the bed is new....
    that's why I'm here trying to figure this out.



  • While I don't have another SSR on hand, I was just now able to find the machine specific MOSFET. I guess I'll be trying that out next.


  • Moderator

    The Duet bed heater mosfet can handle up to 18a so you could connect the bed heater directly to the Duet. No SSR or external mosfet required.



  • @Phaedrux Well, that would answer that question! I'll try that first.



  • That did it! So far at least... When I first got the machine, it was burning out cheap PSUs so the company's solution was to send out new beds and PSUs along with this monster MOSFET. I got an SSR while the boat was coming from China and all was well until a few days ago. The Black Widow was a heavily flawed machine but I have upgraded, rebuilt, and poured a huge amount of time and money into it - and learned a lot. It is currently a tank after this last attempt to get it right. Let's hope it works as it should - thanks repeatedly, @Phaedrux. You caught me in midair again!


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