Heaterfault due to temp drop

[Nxt-1]

I've had a couple issues with hotend heater faults. Mid print the temperature drop rapidly, triggering the build in delta_T safeties. Since I saw the error happening I immediately reset the fault and allowed to heater to heat up again. Only to trigger the temperature rising to slow error before another reset allowed me to continue my print.

Since the part cooling fan was already running and I am using a E3D v6 with a silicone sock I doubt this is what caused the temp drop. I have had this issue a couple times now since updating to the RTOS. I have no idea whether is't related though.

M122
=== Diagnostics ===
RepRapFirmware for Duet 2 WiFi/Ethernet version 2.0(RTOS) running on Duet WiFi 1.0 or 1.01
Board ID: 08D6M-91AST-L23S4-7JTD0-3S86K-1NX1K
Used output buffers: 3 of 20 (8 max)
=== RTOS ===
Static ram: 28380
Dynamic ram: 95972 of which 0 recycled
Exception stack ram used: 428
Never used ram: 6292
Task NETWORK ready, free stack 396
Task HEAT blocked, free stack 824
Task MAIN running, free stack 516
=== Platform ===
Last reset 01:16:58 ago, cause: power up
Last software reset at 2018-06-14 22:34, reason: User, spinning module GCodes, available RAM 6252 bytes (slot 1)
Software reset code 0x0003 HFSR 0x00000000, CFSR 0x00000000, ICSR 0x0041f000, BFAR 0xe000ed38, SP 0xffffffff
Error status: 0
Free file entries: 9
SD card 0 detected, interface speed: 20.0MBytes/sec
SD card longest block write time: 27.2ms
MCU temperature: min 32.0, current 41.1, max 41.2
Supply voltage: min 11.7, current 11.9, max 12.3, under voltage events: 0, over voltage events: 0
Driver 0: ok, SG min/max 0/558
Driver 1: ok, SG min/max 0/526
Driver 2: ok, SG min/max 0/511
Driver 3: ok, SG min/max 0/1023
Driver 4: standstill, SG min/max not available
Date/time: 2018-06-17 11:48:06
Slowest loop: 75.56ms; fastest: 0.07ms
=== Move ===
Hiccups: 0, StepErrors: 0, LaErrors: 0, FreeDm: 213, MinFreeDm 120, MaxWait: 230100896ms, Underruns: 0, 0
Scheduled moves: 43303, completed moves: 43296
Bed compensation in use: none
Bed probe heights: 0.145 -0.141 -0.068 0.171 0.141
=== Heat ===
Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1
Heater 0 is on, I-accum = 0.4
Heater 1 is on, I-accum = 0.5
=== GCodes ===
Segments left: 1
Stack records: 3 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 doing "G1 X14.46 Y1.161 E0.03798" 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 ===
Slowest loop: 14.23ms; fastest: 0.01ms
Responder states: HTTP(0) 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 1.21
WiFi MAC address a0:20:a6:16:ec:ed
WiFi Vcc 3.36, reset reason Turned on by main processor
WiFi flash size 4194304, free heap 15096
WiFi IP address 192.168.178.147
WiFi signal strength -66dBm, reconnections 0, sleep mode modem
Socket states: 0 0 0 0 0 0 0 0
=== Expansion ===
 

[dc42]

The nature of the temperature graph suggests to me that there is a problem in the thermistor wiring.

[Nxt-1]

@dc42 The drop indeed seems to be to steep to correspond to the actual temperature of the hotend. I've check my thermistor cartridge wiring and I did not find loose connections of exposed wiring posing short risks.

I have been working on my PSU, could the thermistor reading be in any way shape or form be connected to PSU problems?

[dc42]

If the 3.3V power rail on the Duet suffered sudden drops then I guess you might see temperature fluctuations. But if you have the internal 5V regulator enabled then the 3.3V rail could only drop if you already had insufficient voltage to run the motors.

[Nxt-1]

@dc42 said in Heaterfault due to temp drop:

If the 3.3V power rail on the Duet suffered sudden drops then I guess you might see temperature fluctuations. But if you have the internal 5V regulator enabled then the 3.3V rail could only drop if you already had insufficient voltage to run the motors.

I do use the internal 5V regulator and did not notice the motors stopping or anything like that. Electrical issues seem to be out of the question then.

I just completed a 3,5 hr print successfully, which is't helping in tracking down this issue I guess hehe.

[Nxt-1]

@dc42 said in Heaterfault due to temp drop:

The nature of the temperature graph suggests to me that there is a problem in the thermistor wiring.

The fault came up again today, so I went trough the usual procedure of resetting and turning the heater on again. Only this time I noticed bumping my printer actually causes a 10-20°C temperature fluctuation, producing a temperature graph I not comfortable posting here. Sadly I was not able to make it fluctuate just by fiddling and wiggling with the thermistor wire/connection.