OpenDRO supports several auxiliary devices that you can connect to your DRO. These devices include tachometers, electronic edge finders, and SD card readers for automation.
The tachometer function is used to display the spindle speed of a mill or lathe. A small probe that optically measures the rotational speed is mounted to the machine. The probe sends a 5V pulse to the DRO through the tachometer connector for every rotation of the spindle. The DRO measures the period between these pulses and converts it to either RPM or SFM for display on the Z/Z2 axis. The tachometer display is updated once per second.
Absolute zeros can be set on the DRO with an electronic edge finder by contacting the work piece with the edge finder while it is mounted in the spindle. Many commercially available edge finders can be adapted for use with the DRO. A circuit inside the edge finder sends a 5V pulse to the DRO through the edge finder connector. To set the absolute zero for an axis with the electronic edge finder, set the DRO to absolute mode and press the ZERO key once for that axis. When the edge finder contacts the work piece, the axis is zeroed at the current position. To compensate for the diameter of the edge finder, use a tool offset with the cutting edge compensation feature.
An SD card reader is available for the DRO-550 if you want to add the ability to read SD memory cards but do not want the LCD-200 and two extra axis displays. The SD card reader mounts inside the DRO-550 case and you only have to cut a small slot in the case to insert the card into.