All About Sync Sensors

What is the purpose of a Sync Sensor?

A sync sensor provides a consistent point of reference in a floppy drive that doesn’t have an index sensor. It does this by sending a signal whenever the spindle that spins the disk reaches a fixed rotational position. By tracking the amount of time between signal pulses, we can determine the rotational speed of the disk. And it also gives us the ability to keep the exact alignment of data across all of the tracks.

How do I pick the correct Sync Sensor for my drive?

There are currently 4 models of sync sensors for various drives. Each is a different color in order to make it easier to identify.

Apple DIsk II (Alps)
Apple Disk II (Shugart)
┬Ásci A2
Rana EliteOne
Apple UniDisk 5.25
Apple 5.25 Drive
Apple 3.5 Drive

As you may have noticed, the Disk II drive is shown twice in that list. That is because early drives used Shugart mechanisms, and later ones used an Alps mechanism. Thee Shugart ones tended to have a rainbow-colored cable whereas the Alps had the gray cable, but that isn’t a guarantee as to which mechanism is really in your drive. Luckily, you can peek through the door on the front with a flashlight and see the shape of the casing. There is a ledge next to the spindle that is part of the casing. On the Alps mechanism this ledge exists on both the left and right side of the spindle (right side drive in picture below). The Shugart mechanism only has it on the right side (left side drive in picture below).

How do I install a Sync Sensor?


How do I test that a Sync Sensor is working?

The Applesauce client software has a tool to help you with testing and the installation of sync sensors. Under the Drive menu, you can find the Sync Sensor Assistant. To use this, you will need to have your Applesauce plugged into your computer and your sync sensor connected to your Applesauce. The Beeper will emit a tone whenever it detects a magnet within sensor range, which is a few millimeters. This comes in very handy when installing your sensor as you can rotate the spindle back and forth to make sure that it is picking up the magnet consistently. After you have your drive closed back up after installation, you can run the Stability Validator that will run a longer test to make sure that it is working well.

How does a Sync Sensor work?