Capacitive Sensor Schematic for Anet A8

thingiverse

The Anet z limit switch is normally 5v and is triggered when the mechanical switch is pushed, grounding the 5v sensing pin to ground. The Capacitive Sensor works by going to ground when it senses a surface. Basically using two rectifier diodes, the Anet board is protected from the higher voltage of the 12 volt sensor, but allows the 5v z limit switch pin to pull to ground when the capacitve sensor senses a surface. I'm using this setup on two Anet A8 printers and they work great and repeatably the same every time for the last year. The 12 volt supply to the sensor is a must, 5 volts is not high enough to provide a repeatable reading. Why 2 diodes? Why not? The second diode is mostly for a backup since we're trying to protect the controller's 5v limit switch circuit from the 12v of the sensor. Parts needed: 1 - Capacitive sensor (https://smile.amazon.com/gp/product/B00542U3M4): Capacitive Proximity Switch; Model : LJC18A3-H-Z/BX; NO; Wire Type : DC 3 Wire Type (Brown, Black, Blue) 2 - Rectifier Diodes (https://smile.amazon.com/gp/product/B008LTJOX6): 1N4004 400V 1A Axial Lead Silicon Rectifier Diodes 1 - 3Pin JST-EH Connector (https://smile.amazon.com/gp/product/B00TGSD6PI) The sensor is mounted in the Anet A8 Front Fan Sensor Mount 18 mm (stl included in this thing): https://www.thingiverse.com/thing:2111157 Note: When setting up the sensor the first time, I start with the hot end a couple of mm's off the bed and the bottom of the sensor about 5-6mm above the bottom of the hotend. You may need to turn the adjustment screw on top counter clockwise several times until the light comes on for the sensor, showing it's sensed the bed. I will usually raise the hot end about 50 - 100mm or so off the bed, then attempt to home, and wave my hand over the sensor to verify that is is indeed working as it starts to come down for homing Z. If it doesn't stop when you wave your hand under the sensor, you may need to kill power to keep your hotend from driving into the bed Use at your own risk, not responsible for damage to your printer.