Error on Thermistors

weput

same fluctuating behavior.. (see video https://www.youtube.com/watch?v=5d328Wj1e_o)

4/3/2020, 10:39:12 PM 	m115
FIRMWARE_NAME: RepRapFirmware for Duet 2 WiFi/Ethernet FIRMWARE_VERSION: 3.01-RC6 ELECTRONICS: Duet WiFi 1.0 or 1.01 FIRMWARE_DATE: 2020-04-03b3

if i pull the sensors off they stay at -273.

my config

; Heaters
M308 S0 P"bedtemp" Y"thermistor" T100000 B4138         ; 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
M143 H0 S120                                           ; set temperature limit for heater 0 to 120C
M307 H0 B1 S1.00                                       ; enable bang-bang mode for the bed heater and set PWM limit
M140 H0                                                ; map heated bed to heater 0
M308 S1 P"e0temp" Y"thermistor" T100000 B4725 C7.06e-8 ; 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
M143 H1 S305                                           ; set temperature limit for heater 1 to 305C
M307 H1 B0 S1.00                                       ; disable bang-bang mode for heater  and set PWM limit

weput

@Danal said in Error on Thermistors:

it

ok

not sure why i went this route; but downgraded back to 2.05.1 before pulling out the multimeter. Definitely a hardware issue.

I shorted one VSAA pin to ground (while powered from USB) to ground and intermediately got a reading on both thermistors.

Dunno how this happened; but before what im reporting i found the printer halted with thermistor error:

must had shorted something while replacing the thermistor...

anyways, with this covid-19 lockdown; im not gonna be able to replace the fuse

A Former User

@weput said in Error on Thermistors:

I shorted one VSAA pin to ground (while powered from USB) to ground and intermediately got a reading on both thermistors

thats more or less the part I was hoping you'd go for

@weput said in Error on Thermistors:

anyways, with this covid-19 lockdown; im not gonna be able to replace the fuse

you could run with the short, but you run the risk of more damage if something shorts again; or if you have any low value fuse you could use that in a similar manor as the short as a temporary or permanent bandaid.

(edit: if you're tempted to operate the printer with a temporary short across the VSSA fuse use the thinnest single strand of wire you can find - super flexible silicone wire for instance has an OD of 0.08mm for a single strand and it will effectively act as a low value fuse) nope, still carries too much current

dc42

@weput said in Error on Thermistors:

@Danal said in Error on Thermistors:

it

ok

not sure why i went this route; but downgraded back to 2.05.1 before pulling out the multimeter. Definitely a hardware issue.

I shorted one VSAA pin to ground (while powered from USB) to ground and intermediately got a reading on both thermistors.

Dunno how this happened; but before what im reporting i found the printer halted with thermistor error:

must had shorted something while replacing the thermistor...

anyways, with this covid-19 lockdown; im not gonna be able to replace the fuse

It sounds to me that you may have a lot of leakage between one of the thermistor wires and VSSA. That leakage is likely to get worse and damage something. The VSSA resettable fuse protects against that kind of damage.

Try disconnecting one thermistor at a time from the Duet, then see if you get a stable reading from the other one without shorting VSSA to ground.

weput

@dc42
I did that... No luck.

Duet WiFi 1.0 or 1.01

Fuse is blown.

weput

@bearer
I'm tempted to do that.

I placed my cheap analog multimeter in ohmimeter between vssa and gnd and got a reading. (120 or 1.2 kilo ohms... Can't be sure anymore)

Digital states open...

Unfortunately I don't have much at hand to fix this.

A Former User

@weput said in Error on Thermistors:

I'm tempted to do that.

if the unstable reading is persisting, then as dc42 suggest its not adviceable.

Otherwise any 100mA or smaller fast acting fuse will provide some protection if wired between VSSA and GND.

weput

@bearer that's the thing...

It's not going to be easy to find a fuse that small with the Lockdown.

A Former User

Its your call, the fuse did blow because of a short on your thermistor - if it happens again without a fuse something else will blow.

weput

I'll make a permanent short and check the reading for like 10 mins...

I don't want to blow the board but I assume is better this than setting one of those old 8 bits on.

dc42

What hardware revision Duet is it?

weput

@dc42 said in Error on Thermistors:

?

This is one of those preorders boards... (numbered 138) preorder group 2.

so i assume hardware ver1.0

dc42

@weput said in Error on Thermistors:

@dc42 said in Error on Thermistors:

?

This is one of those preorders boards... (numbered 138) preorder group 2.

so i assume hardware ver1.0

Thanks. See https://duet3d.dozuki.com/Wiki/Connector_and_spare_part_numbers#Section_VSSA_fuse.

weput

@dc42 Thank you.

I've seen that... unfortunately with this covid-19 lockdown i assume i'll have to install and run on 8 bits for a while.

dc42

In the UK at least, the major component distributors are still shipping components. What country are you in?

weput

@dc42 said in Error on Thermistors:

In the UK at least, the major component distributors are still shipping components. What country are you in?

Panama.

dc42

If you have a resistor with a value in the range 2 to 10 ohms, you could temporarily connect that between VSSA and ground instead of the fuse. Space it well off the board, because it will burn up if you get a short between VSSA and VIN - which may be what caused the VSSA fuse to blow.

clearlynotstef

Personally I used a tube fuse and little holder thing, but you could even solder directly to the fuse if you could get one of them. There's gotta be someplace still selling standard fuses online near you

https://www.amazon.com/dp/B00X7B6FPI/ref=cm_sw_r_em_apa_i_TyFIEb1C2DN29

https://www.amazon.com/dp/B00VLBAF84/ref=cm_sw_r_em_apa_i_bFFIEbQQWNZKN

weput

ok guys...

we are still in lock down so no luck to getting the fuse or the resistors...

(im fine as i have another printer running...)

Anyways, I'm thinking on breaking one of those x-mast decoration light cords (the ones that comes with like 150 small bulbs wired in series) to use one incandescent bulb... its a low resistive lineal load and if something happens it should manage the power by emitting light...

.,.. then i recalled i have a few small led's laying around... technically the same principle with the 0.7v drop.... anyways,

here im asking.. what do you think?

A Former User

is there not a gas station or anything like that you can get a fuse from? (they might not have very small values though, but might for motor cycles)