The Original Prusa i3 MK3 is the successor of the award-winning Original Prusa i3 MK2 3D printer.

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Problem with the filament sensor

During the self test. I keep getting a filament sensor wiring error. I have chk both connections and they are connected correctly. I have used a multimeter on all the wires and power is flowing from one connection to the next on all wires. What could the problem be?

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Hi David,

the filament sensor can be faulty, please contact our support using live chat or email (info@prusa3d.com)

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How do I access the live chat ?

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Hi David,

please see the Step 7 : 1. Introduction

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I have the same problem. But my sensor worked during pre-flight and now it does not. I ohmed the cable.

Found the GitHub section with the schematics. The Red and Black wire +5VDC which Black wire being ground

The Blue and white wire have 4.7K ohm resistors to +5V

Test procedure.

1) cable connected to controller Red=5V, Blk=gnd,

2) cable connected to sensor Red resistance check: to Blue wire=4.7K ohm, to White wire = 4.7Kohm

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My sensor has been misswired and the self test failed. After that I corrected the sensor wiring but the self test does not succeed. I measured the cables as you did and the resistance and voltages are correct. I wonder if I managed to fry the chip on the sensor.

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Hi, in case the sensor doesn't work, recheck the connections are according to the manual (guide) and if so, please contact our support info@prusa3d.com

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I'm having the same problem; have rechecked all wiring, tested the cable, and inspected the sensor for visible damage or debris. No response from info@prusa3d.com (sent 12 Apr). Please help.

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Hi Christopher, I will alert colleagues to get in touch with you.

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It depends what your wiring error your found was.

If the red and black wires were reversed (+5V and Gnd). Then yes the chips are damaged with the current board rev 0.1

If the board has a fuse on it F1 then the fuse is blown and I would get another sensor. Put you could bypass the fuse and try again. Note this is a very new board it might not be out

If the other colors are swapped then you are ok.

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I have the same problem.

My filament sensor self test failed.

I had:

Rechecked all wiring, both cable ends colors sequence to pins are correct, white above on sensor and red to the outside in the main board bottom shelf. Tested cables for continuity, inspected the sensor for visible damage or debris, checked OK the 5A fuses.

I was careful to keep the sensor wrapped to protected it against static and I placed it using the wrap.

Sensor doesn't have a pilot light on, It would be nice miniature led.

This laser sensor uses the I2C protocol which is amazing, Red to black voltage has to be 5VDC to enable the sensor, and one 4.7kΩ pull up resistances to each SCL blue and SDA white ports (then from red port can be easily checked ) they are the communication and control I/O. Mine is a Rev. 0.2e

I am not receiving the 5VDC so probably the main board is defective.

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same issue here, 5 v ok , wiring ok , Pullups ok, selftest fails

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removed sensor, measured voltage behind the ‘new’ 50 mA fuse. voltage only 2.5 v. Need new sensor or are these fuses resetting ?

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David gallegos will be eternally grateful.
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