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New filament sensor on Github  

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stahlfabrik
(@stahlfabrik)
Honorable Member
New filament sensor on Github

https://github.com/prusa3d/PRUSA_Laser_filament_sensor

rev 02e

any ideas on what has changed? (have not looked into it yet)

Edit: so there is a fuse? and a resistor added? I guess it is to prevent the melting issue? But not necessarily improve detection reliability? What do you think?
https://github.com/prusa3d/PRUSA_Laser_filament_sensor/blob/master/rev.02/laser-sensor.pdf
https://github.com/prusa3d/PRUSA_Laser_filament_sensor/blob/master/rev.02e/laser-sensor.pdf

Posted : 14/05/2018 4:53 pm
vaxxi
(@vaxxi)
Estimable Member
Re: New filament sensor on Github

There's a resistor (current limiting) and what looks to be a varistor/thermistor added (probably also for current limitation). Don't think it has anything to do with filament detection, more likely to prevent overheating/burning out the sensor.

Posted : 14/05/2018 5:01 pm
TJH
 TJH
(@tjh)
Trusted Member
Re: New filament sensor on Github

I see two differences in the schematic

1) Addition of 200 k pullup from Vref/EN to +5V. This resistor is shown in the TI data sheet app note for the LSF0102 level translator.
The data sheet says explicitly
The 200 kΩ, pull-up resistor is required to allow Vref_B to regulate the EN input. A filter capacitor on
Vref_B is recommended.

It's not likely that the lack of this resistor causes burn out, but it (and the missing filter cap on vref) might explain some of the mal-performance.

2)There's now a 50 mA fuse on the 5V input. This should prevent burning in case of mechanical damage/short on the board.

They should add the filter cap as recommended on the datasheet.

Posted : 15/05/2018 4:03 pm
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