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Plastic Beach - Water Wave Machine

hydrophyte

hydrophyte

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22 Aug 2009
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Plastic Beach - Water Wave Machine

I've been pondering this idea for a while and I've finally put together a design for experimentation. My goal is a machine to create traveling waves in an aquarium like wind-driven waves in a natural body of water. These differ from the kind of water movement generated by reef aquarium wavemakers as they would have rhythmic crests & troughs and directional movement down the length of the enclosure.

With a search you can find several videos with machines achieving this for educational and scientific purposes, or just for fun. But none of the ones I have seen really integrated the concept as a display aquarium with livestock, plants and other ecosystem features.

Here is a really interesting video from MIT with clips showing sand ripple development in a large wave tank...

YouTube: Dynamics of Wave Ripples

Most of the examples I have seen used a hinged paddle at one end of the enclosure and actuated with a servo motor or other mechanism. For my project I wish to make the most efficient use of the limited lengthwise space in a glass tank, while also designing the machine as an appealing kind of kinetic sculpture. So I opted instead for a cam & follower mechanism with a stepper motor supplying power. Here's the whole deal in operation with the 6-gallon bookshelf tank...

22-I-23-Plastic-Beach-IV.jpg


Here's another example with a wave machine that works in a similar way with a wedge-shaped paddle...

YouTube: Miniature wave tank

I have an idea in mind for a sloping 3D-printed beach to break the waves at the tank far end, but for now I've just piled up these lava rocks. They work OK. Without some kind of physical dissipation, the energy will just bounce back to the middle of the tank to create standing waves...

22-I-23-Plastic-Beach-II.jpg


There are some cool ideas to explore with wave height, length, frequency and other parameters. I have this microcontroller + stepper driver set up with a rotary encoder and LCD display to toggle the motor on & off and control other signals. Luckily I got some help with this because I'm really not great with code and electronics...would have otherwise taken me forever to figure out...

22-I-23-Plastic-Beach-I.jpg


I'm going to run this for a week or so and then design a version 2.0 with smoother operation (I hope) and nicer fit & finish. This is most likely going to be a brackish water system with moderate salinity and appropriate organisms. I'll explain some more of that later on as I get it organized.
 
Evansss said:
This looks great. Can’t wait to see how it turns out
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Thanks very much.

I've rounded up some more parts for the revision. The cam assembly is going to be a little different.
 
Dogtemple said:
This is awesome. Out of interest does the stepper motor create noise an vibration?
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I was able to pretty much silence the motor with microsteps. Here' s an explanation...



Microstepping significantly reduce torque, however, and at slow rotation speeds (higher microsteps) the cam mechanism gets stuck. So I'm going to need to either install a bigger Nema 17 or work on some other solutions.



.
 
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hydrophyte said:
I was able to pretty much silence the motor with microsteps. Here' s an explanation...



Microstepping significantly reduce torque, however, and at slow rotation speeds (higher microsteps) the cam mechanism gets stuck. So I'm going to need to either install a bigger Nema 17 or work on some other solutions.



.
Click to expand...

Have you considered field orientated control? That will give you high torque at low speed.
 
Dogtemple said:
Have you considered field orientated control? That will give you high torque at low speed.
Click to expand...

How does that compare for noise? The motor needs to run pretty much silent. Any guidance anywhere? With a quick search I don't see much.

With microsteps the driver is also running really hot and this is something else I have to resolve.
 
hydrophyte said:
How does that compare for noise? The motor needs to run pretty much silent. Any guidance anywhere? With a quick search I don't see much.

With microsteps the driver is also running really hot and this is something else I have to resolve.
Click to expand...
well it’s a bit of a magical solution and you’re right, there’s not much out there. It’s quite advanced but someone has made it accessible. Check out simplefoc and look on YouTube for examples.

It will run very quiet, won’t get hot and use much energy, will give high torque and low noise. Gives very precise control too if you need it.

I am building something (nothing to do with aquatics) using FOC as I need a small, super slow, silent, high torque motor that can fit in a small space. It sounds to good to be true but it’s out there and runs from an Arduino so easy to do with low cost.
 
I designed and built the Version II with several improvements:
  1. The follower (along with the second span thingy [?]) now has a spring connection with the two pushrods and this is much better.
  2. The new cam is egg-shaped, so it completes the extension motion in 1/4-revolution, rather than a whole 1/2-revolution like the simple off-center circle shape. The important effect here is that the machine can create higher amplitude, but longer wavelength waves without such fast rotation.
  3. Instead of a second follower above the cam, a length of elastic returns the follower assembly after each extension.
  4. They're not really essential, but I incorporated polymer linear bearings for the pushrods and I like how they look.
I need to work on the torque and heat problems. I'll have to study the FOC concept some more because that looks like the most effective solution.

The router gave me some trouble and wasted some material with a couple of bad jobs, but I think I figured out the problem.

6-II-23-Plastic-Beach-II.jpg

6-II-23-Plastic-Beach-III.jpg

6-II-23-Plastic-Beach-IV.jpg

6-II-23-Plastic-Beach-I.jpg
 
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FISHnLAB said:
This is a really neat project Hydrophyte and nice work on the build👍. I look forward to seeing it work. I hope you will post a video?
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Yes I watched that video from Australia as well. Really interesting. I will be very pleased with this project if I can get sand ripples to form. If I can get some good results, I'll post a video or two to YouTube.

This setup is too small (less than 2 gallons of water) for fish, but I want to also try a larger setup with livestock. Some kind of small, active, silvery fish like the kinds you might find in beach areas would make a nice display. White Cloud Minnows or a small Danio would probably work.
 
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A little more progress...

I improved the support post with a piece of 80-20 integrated into the shelf frame and this looks much better—don't know how that didn't occur to me originally.

Also wired up some lighting with four little 1-watt downlights that I had here on-hand. This should be enough light for the small easy plants to be scaped into the beach area.

Stepper motor is updated with a bigger Nema 17 variant for more torque. I still need to get the little 4-wire connector to plug into the driver, so I was not able to fire it up tonight.

resize-6-II-23-Plastic-Beach-II.jpg

resize-6-II-23-Plastic-Beach-I.jpg


resize-6-II-23-Plastic-Beach-III.jpg
Als
 
Myrtle said:
I can't wait to see this running. The engineering side is all way over my head but I'm enjoying feeling intelligent by proxy!
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Thanks for following along! I'll try to get water in this thing tonight.
 
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