=========Below here be dragons==================================================
This stuff not needed to use the lathe, mostly collecting things as I find them in case we ever want to upgrade the Lathe to a better controller.
Auto Tool Changer. The ATC unit runs from a DC motor driving the tool turret via a worm Gear. There are 3 sensors (optical) that give a grey code encoded tool number as the turret rotates. The tool is selected by putting 24 volts on the DC motor, the turret starts turning. Monitor the 3 sensors, when they have the correct tool number the DC voltage is reduced to 12 volts and the polarity is reversed. This causes the toolpost to reverse and lock. The 12 volts reverse polarity is maintained to keep the tool locked in place. Diagrams of the tool changer board below.