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 # PRUSA Laser filament sensor
-KiCad PCB layout
+
+Filament presence and velocity detection using a [PAT9125EL optical laser movement sensor](http://www.pixart.com.tw/product_data.asp?product_id=173&productclassify_id=18&productclassify2_id=51&productclassify_name=Optical%20Tracking%20Sensors&productclassify2_name=Consumer&partnumber=PAT9125EL-TKIT%20PAT9125EL-TKMT), operating at 850nm.
+
+See also:
+* [PAT9125EL datasheet](http://www.pixart.com/upload/PAT9125EL_GDS_V1.2_31052017_20171011150843.pdf)
+* [boucaron's investigation into this board](https://steemit.com/printing3d/@boucaron/prusa-mk3-filament-detector-short-study)
+
+# KiCad PCB layout
 ![PCB](rev.02/laser-sensor.png)