Wall Mounted Hydroponics (In Progress)

 Wall Mounted Hydroponics

 

 

For Christmas this year, my wife wanted me to build her an indoor hydroponics system. During the summer months we always plant a garden, even if it's small. We love the fresh vegetables and herbs, and it adds a really nice ambiance to our backyard. But when winter comes, and we have to give all that up, we struggle through without fresh mint. It's probably the hardest part of winter. Though, I do hear a lot of complaining about the cold...

When she mentioned the idea of building one of these, I was immediately interested. There is something special about combining digital control with fluid handling, to grow plants inside. And if there is one thing I can't pass up, it's the opportunity to significantly over complicate the process of obtaining tomatoes and basil. 

My hydroponics system is a combination of nutrient film technique, and ebb and flow. Using PVC for the main structure, and nylon tubing to pass the nutrient around.

Netcup Standoff

From the outset, I wanted to incorporate 3D printing somehow. I own three 3D printers after all, so I'm going to have to incorporate those into every project from now on I think... To that end, I came up with what I think is a fairly clever use.

Plants are grown in some sort of growing medium, held by a plastic net cup (black, in the below picture). It's very important for there to be some space between the top of the water, and the top of the roots, to allow them some room to breathe. Since they normally can extract oxygen from the moist dirt, it's very possible to drown a plant if the roots are constantly and fully submerged. 

So, to keep the net cup out of whatever water sits in the pipe, I designed these standoffs. They hold the netcups a few inches above the water, and the plants roots will eventually reach down to access the nutrient.

In this picture, you'll see two different sizes of standoffs. As I mentioned before, it's a combination NFT and ebb and flow - for very young plants that don't yet have long roots, you can place them in the short standoffs and when the pump runs to replenish the nutrients, it soaks the growing medium of the shorter ones. (At the moment I have the pump running once per day.... I don't honestly know what a proper cycle should be yet)

 

 

Hidden Nutrient Reservoir

It was made very clear to me, that the nutrient reservoir should not be in the dining area, but instead should be behind the wall in the pantry. That meant of course running the hoses through the wall. And, as you can imagine, this was the perfect time to use my 3D printer for a wall plate to make the holes in the drywall less drilled looking.

 

 

It does actually add a nice polished look to an otherwise industrial looking focal point of the room.

In the below picture  you can see the mess of wires and hoses that interact with the nutrient reservoir. I think putting all of this behind the wall was the right call in the end.

I have a basic submerged pump, an air pump to keep the water aerated, and a fish tank heater to keep the water at 78F, since it's winter and I'm hoping a little boost in temperature will help them grow more consistently. In this picture you'll see a couple of wifi plugs. These will get swapped out my a more complex system. At the time of writing this, I have no yet completed that, but we'll talk about the strategy in further sections.

 Worth noting, is that the system does not drain as fast as it pumps. I used the same size hose on the inlet and the outlet, which may be the contributing factor. So it is paramount that the pump does not run for more than a minute at a time, otherwise I will easily get overflowing. An attempt to remedy this was to add an air vent to the outlet. It seemed to help a little, but not nearly as much as I was hoping that it would.

Control System

Just like I can't avoid inserting 3D printing into every project, it's also hard to avoid adding some kind of digital/electronic/control systems as well. The WiFi switches weren't working very well for me any way, and I've wanted to build something like this for quite some time. 

The overall plan is to build a four switched outlets powered by a RaspberyPi Pico W. With four inputs for connecting temperature probes (or other sensors) if needed.

I started with the electrical work, routing power through a bank of relays. As well as a 5V power supply for powering the low voltage side.

And that's as far as I've gotten! As I progress I'll update this.

Bill of Materials

Nearly every thing I used was pretty easy to source. Here it is:

Main Structure

1. 8ft of 3" PVC
2. 4 x 3" end caps
3. 4 x 3/4" reducers
4. 4 x 3/4" x 1/2" push fit elbow
5. 4 x 1/2" NPT to hose barb
6. 20 ft of nylon tubing
7. Shelving brackets

Nutrient Handling

1. Water pump
2. Air pump and stone
3. Aquarium heater
4. Food safe bucket
5. Wifi switches (If not using the custom system) 

Control System 

TBD

Electroplating - Nickel

Nickel plating has a number of advantages over copper. Primarily, it doesn't tarnish. It can also be polished to a shiny silver. Not quite to the same degree as chrome, but it's easier to do.
 

Nickel doesn't plate well directly on to the graphite paint. It has a much better adherence when there is a layer of copper underneath.  You can read about how this is done in my other blog post.

Once you've got your copper layer, it's time for the nickel.

Copper plating requires the metal salt copper sulfate to act as an electrolyte. Nickel uses nickel acetate. It's possible to buy this online, but it's not quite as readily available as copper sulfate. So we're going to make our own.

The process is simple, if we force nickel ions to dissolve in a solution of acetic acid (vinegar) it will form nickel acetate.

Buy some basic distilled vinegar from the grocery store. Fill a jar with it, add a pinch of salt. Then attach pure nickel to the anode and cathode of your power supply. Running at 5 - 10 Volts it will take 12 - 24 hours to get an adequate solution. Pictured below is after just a few hours.

After you have your solution, it's the exact same process as the copper plating.  I won't go into that here. but you can read about the process in the other post :)

One thing of note, is nickel is a hard metal. About as hard as steel. This makes it hard to polish with steel brushes (Unlike Copper). So you have to use something a little more serious. Once I figure out how to use polishing compounds I'll write a post about that one too :D

Electroplating 3D Prints - First Real Attempt

When I first discovered that electroplating 3d prints was possible, I got very excited. The idea that you can print something to a specific design, and then give it metallic properties was interesting to me.

There are a few reasons you would want to electroplate a 3d print.

1. It increases the strength and rigidity of the part.
2. It's conductive.
3. It's pretty.

A note on the conductivity. It's a common practice to use electroplating to make double sided PCBs with through hole components by electroplating the inside of the hole. Sure you can just use solder and some wire, but that's way less cool.

You can electroplate many different kinds of metals. They each have different requirements and benefits, and some can be quite complicated. So for this walk through I'm going to be demonstrating copper and nickel. Both of which are fairly easy to do (And so far the only two I know how to do :] )

Copper, just like silver, has the drawback of tarnishing over time. If you leave either exposed to oxygen for too long the finish will dull and possibly even discolor. I haven't tried it, but I bet if you covered the copper in some sort of varnish it will prevent the tarnish.

But if for some reason you don't want to do that, or you want a silver finish, nickel is the common choice. Nickel doesn't plate well directly to the 3d print. It works far better if there is a base layer of copper, and then the nickel is plated on top of it. But Nickel doesn't tarnish. And it's a good poorman's alternative to chrome. Since chrome is more complicated to successfully plate.

Let's start with copper plating.

For a 3d print to be electroplated, the surface needs to be conductive. There are a couple of clever ways that I've seen this accomplished. You can buy conductive filament (Which is expensive). You can mix graphite power with acrylic paint (Which is a very attractive option with some nice benefits). Or you can mix acetone and graphite power to make paint that only works on ABS.

Preparing the printed part
 
The process that I chose is using ABS with acetone and graphite. Graphite can be bought online, and if you're lucky at a local artists store. It's not very expensive, and the bottle will last you a really long time. Acetone can be picked up at your local hardware store.

Once you have your to ingredients, you'll mix them together in a glass container. A Mason jar works really nicely.  The proportion doesn't really matter. You want it thin enough that it can paint smoothly, but not so thin that it doesn't completely cover the printed part. I'm using white ABS so that it's very obvious when I don't completely cover the part. If you're not using a light color, just make sure that you coat it fully.  Side note, it's a good idea to not touch the painted part with your bare fingers. The oils in your hands can cause the part to plate unevenly.

After the paint has dried (Which should take a few seconds) use some fine steel wool to buff the painted surface. You can be pretty rough with it here. The graphite binds pretty tightly to the abs. If you do happen to scrape off the paint, reapply, and buff a little more gently.


Preparing the plating solution

For plating copper I use a mixture of copper sulfate and vinegar. Traditionally sulfuric acid is used instead of vinegar. but for small setups like this, I'm not so sure it's necessary. But the solution being acidic helps improve the conductivity, and helps maintain the copper ions in the solution.


Plating

Finishing 
The final result! It comes out rather rough, and needs some good polishing. But it's solid copper. You'll notice some parts didn't plate at all. I'm not exactly sure why. It may be because it's a deep "concavity". Or it may be that when I rubbed it with steel wool I didn't get in between the letters well enough.  Either way, I think I'll be able to do some selective plating and touch it up

I happened to have a brass brush tool for my Dremel, so I decided to give it a try. I think it turned out pretty nicely.