extruder help

having some weird issues with my extruder.
as soon as i plug it in before i even start the host software my extruder start heating up. now it wasnt doing this before, is just a recent development.

also, my temperature seems to be starting at 28c and goes up, I'm a little confused on where and how to fix this.
any help would be awesome

Try pressing the reset switch on the extruder controller, as well as the motherboard.

The heater probably starts at 28C because that's the room temperature. :-)

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-Nudel
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Perhaps it is the MOSFET that is short circuited. Where did you get your electronics from? Are the MOSFETs NIF5003? I have come across companies supplying electronics with different MOSFETs that are not protected against static damage, so unsuitable in this application.

The low temperature reading of the thermistor is not particularly accurate in the circuit that is optimised for higher temperatures. You tend to have to calibrate it for the particular thermistor to get it even close.

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[www.hydraraptor.blogspot.com]

I'm using techzone extruder board, & it was 25c.. coincidentally that's how warm it is in the house -_-' i haven't tired plugging back in the extruder heater as of yet. i tried resetting before i unplugged it all, and didn't seem to have any effect. After reloading the firmware it may help, i'll post my finding shortly.

I had one of my output MOSFETs fail on my TechZone extruder board. The symptom was the same. As soon as 12 V was applied to the extruder board, the heater would start heating (and its light was on). Another symptom was that if I probed the gate voltage when I switched the heater on and off, it was only being driven to 2.8 V or so (it should be 5V when an output is activated). This may be a design fault (perhaps inappropriate MOSFETs as Nophead suggests), or I could have shorted the heater because I was fiddling with resistor heater block designs at the time.

I just moved the heater to the next set of outputs and modified the pin definitions in the firmware (swapped the pin numbers for the two outputs) and I was back running again. (Thanks Araspitfire on IRC for helping with that).

hrm, ok.. I'm using the newer techzone a-d one wire.. and all you did was just changed the heating ports? on the extruder board?

I moved the heater wires from the port labeled C+C- to the port labeled B+B-.
I changed Extruder/configuration.h like this:

// MOSFET drivers

#define BED_OUTPUT 15
#define FAN_OUTPUT 12 // was 11
#define HEATER_OUTPUT 11 // was 12

Uploaded the new firmware to the extruder board.
Started printing