- Digital Readout -
The display unit
The Display unit is based on separate circuits for each axis. Data from the sensor is received via the serial interface of the Austria Microsystems AS5311. A single PCB contains the power supply for the logic and 3 separate display units controlled by 3 Atmel ATMega8 microcontrollers.
Two push buttons and one LED are connected to the PCB to zero the scale and to switch between absolute and relative mode. The relative mode sets the display temporary to zero. The LED displays relative mode. The zero button is also used to enter the menu (see below).
Initially the PCB was also designed to communicate with caliper based measurement systems. I never finished this part of the firmware.
The software for the ATMega8 is written in C using AVRStudio and WinAVR software packages. Both source and a pre-build HEX file are included in the project. You will need an external programmer to program the ATMega8 because the ISP-Pins are used by the circuit.
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. Some components, like connectors and capacitors, are populated on the bottom side of the PCB. This allows mounting the PCB behind the front of a case. More information is available in the documents within the project files.
Settings can be stored within the controllers EEProm via a simple menu that is entered by pressing the zero-button for about one second:
- Toggle between inch and metric display.
- Enable lathe mode. This will double the distance shown.
- Revert display direction.
- Set position of decimal point to switch the resolution between 0.01mm or 0.001mm.
- Toggle between rounding the last digit to 5 or full resolution.
- Display magnetic field strength for sensor adjustment.
- Display AS5311 flags.