That's a PCA9685, here's the datasheet: https://cdn-shop.adafruit.com/datasheets/PCA9685.pdf
In short, the PCA9685 takes max 5.5 V power, it takes commands from the Arduino and addresses the commands to any of the 16 outputs. Each output has the GND, the V+ and the PWM signal that go to the servo. But the V+ is the same line as the max 5.5 V input, right? The datasheet mentions 400 mA as a maximum current running through it. If I don't want to run some 8000 mA through it, I assume I could connect my servos directly to a juicy 6 V power source (like a led battery). I mean the V+ of the servo to the (+) terminal of the battery and the GND to the (-) terminal and only the PWM line of the servo to the PCA9685. The PCA9685 and the Arduino would share a 5 V power source. All units would share the same GND. Would this work?
550mA is an optimistic value - for an initial guess assume 1A for peak draw of active servos, and 0.1A for
ones not loaded or moving, i.e. at least 15A supply for 64 with 10 active.
If the servos have mechanical load (force) on them when stationary they will consume more power,
so you should take some measurements under load from the actual mechanical setup.
What a lot of people get wrong is assuming a multimeter can see the peak current values - it can't
(well cheap meters can't see the narrow peaks at all).
You would need some sort of current probe and a 'scope to see the full story of the current spikes,
especially if the servo is continually being fed a changing target position. Stall current in a motor
doubles when you try to reverse it when already moving, a fact often forgotten.
Another issue you will have to deal with is that at power up all the servos will want to set position
simultaneously, and might demand more like 64A for one brief instant...
The servos will pull the keys of a pump organ. In action, each servo will have only two positions. In the resting position there's no force at all on the servo. When activated, the force still is not very much.
Before power down I put all servos in the rest position. At startup I hope all servos would be in their rest position.
Before you dash into hardware have a think about how you will get your software and timings to work in this project - sequencing these servos and their travel times may cause issues - I would start with say 4 servos to show up any issues .
