- Digital Readout -
The encoder unit
For each axis, you will need one encoder circuit. It is based on an Austria Microsystems AS5311 encoder that has an internal resolution of 488nm. The encoder unit is connected to the display unit using a shielded cable with at least 4 wires plus shield. The cable is soldered to the encoder PCB. Please refer to the documentation in the project file for cabling schematic. The AS5311 has different modes of operation: In this case it is interfaced to the display using serial mode. Incremental mode is supported by the circuit but not used.
Building the circuit
Extended gerber files and drill files for the double sided PCB are included in the project. They will be accepted by most PCB manufacturers. There are also fabrication files for a panel with one display PCB and 4 sensor boards with 1mm gap between them for separation with a small (table) saw.
The smallest SMD components used are 0805. The AS5311 itself has a 0.65mm pin pitch and must be placed very accurate in line with the PCB. More information is available in the documents within the project files.
A small case that holds the encoder board is relatively easy to build. There is much more information in the project files like drawings of the case i manufactured using a CNC mill. The sensor board should be covered with epoxy or silicone inside the case when you intend to use coolant fluid.
The AS5311 can be used with encoder strips with a magnetic pole length of 2mm over both poles (North + South). On the links page, you can find a selection of sources for this kind of strips. They are usually self-adhesive and covered with a stainless steel strip. The strips should be mounted in a grove that is milled to the width of the strip to protect them. The sensor, together with the strip, should be protected from chips. The distance between the sensor and the encoder strips cover tape should be around 0.1mm. I covered the sensor using 0.1mm film tape and adjusted the sensor to minimum distance. More details on mounting the sensor can be found inside the documentation.