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Things I learned from Version 2

A project log for Open Source Ultrasonic Phased Array

Documentation of the 3rd generation of my ultrasonic phased array project. Levitating stuff, directional speaker, haptic feedback and more!

Niklas FauthNiklas Fauth 07/03/2018 at 12:220 Comments

This isn't my first phased array that I built. Actually, my seconds version is working perfectly fine and has all features I wanted to have. Still, I don't feel like that's what people should read about when considering building their own arrays. And here is why.

First, some specs about V2. I won't go too much into detail, anyway feel free to ask questions if you want to know something particular.

Some pictures:

When I started this project, I didn't know anything about phased arrays. There were some papers about the theory of operation and the maths behind it, but they all used simulations for their proposals. I tried contacting the guys who made this initial levitation youtube video, without success. I knew that I would need to control the transducers individually, and I knew that I need a lot of them. However, I didn't knew if there is a minimum amount of transducers that is necessary, and more important, with what resolution I need to control the phase. And because I wanted to be sure that it works in the end, both of these parameters turned out the be complete overkill in my design. I built a highly sophisticated, completely overengineered array with 19x19 transducers, 10 bit (1024 steps) phase resolution and 8 bit (256 steps) power resolution for each transducer, that, because if this, caused me a lot of trouble. 19x19 because that's the amount of transducers I was able to stick to my fpga, and 10 bit resolution because I was worried a lot that I would need super high resolution for everything to work smooth.

Well, turned out 5 bit (32 steps) are totally fine, and 19x19 transmitters is complete overkill. Not only did this false assumption wasted a lot of time and money, it also caused lots of troubles that are directly connected to this overkill: Thermal problems, high error rate because of the insane amount of components etc.

Especially, I wanted version 3 to be more rebuild friendly. To achieve that, I wanted to change few things:

Anyway, not everything was bad with array version 2. Things I really enjoyed about it:

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