The Multi-saw Edger Controller is used to accurately position circular saws for cutting timber in widths varying from 50 mm to 350 mm or more. The project have three saws on a shaft, with Saw 1 being fixed to the shaft and Saws 2 and 3 sliding along the shaft with bi-directional hydraulic actuators.
The moving saws are also coupled to magnets that move close to a Balluff position transducer. Saw 2 is coupled to an electromagnet and Saw 3 is coupled to a permanent magnet. If the electromagnet is energized then the transducer output will be a voltage proportional to the displacement between Saw 1 and Saw 2. If the magnet is de-energized, the output will be a voltage proportional to the displacement between saw 1 and Saw 3.
The controller use Atmel Mega161 or 162 microcontroller. The analog inputs are measured by a Maxim MAX1270 12 bit ADC. A 74C923 chip scans the keyboard and generates an interrupt on each key press. All power switching is done by zero-crossing triac switches and heavy duty relays.
Charles Kosina, the project designer, explained that up to 48 standard sizes may be stored arranged as four banks of 12. One key cycles through the four memory banks and 12 keys select pre-programmed size. The Set Size, Memory Bank number, Actual Size and Output belt position are displayed on an LCD module. A safety interlock input detects when timber is passing through saws and inhibits any saw movement. Setting up of standard sizes and system calibration is all done from the keyboard. The switch functions are re-defined when in the Setup Mode.