Aquaponics - $2 sequencer

One challenge people have when designing an aquaponics system, is to make the best of the containers you have. This can sometimes mean getting by with a sump that's not quite big enough for a fish tank that nearly runs dry because you have a lot of garden beds.

One solution to this is to use a sequencer. This is a device, that through one method or another distributes water, first into one grow bed, then into another. This allows a better ratio of grow bed filtration to fishies supported because as one bed is draining back into your fish tank, the other is filling.

When I was testing The Invention Engine the other day, trying to come up with a slow flow siphon, I came up with another question that I thought would make yet another test.

I wanted a better sequencer. One that was more reliable, and much cheaper and easier to make.

I've so far made two different designs.

My first sequencer used a balance beam approach, the second, externalized sequencer, used a sprinkler, the third uses offcuts of, you guessed it PVC, a ping pong ball, or foam craft ball. I don't know what a craft ball is for but you can buy them at craft shops and they are a ball made of polystyrene. They cost a few cents each. I bought some a while ago to make coconuts. I was invited to a Hawaiian party and went as a palm tree.

So here's a thing about the universe....

If you get something that floats, but fits snugly in a hole in the bottom of the vessel , it stays stuck to the bottom by water pressure when you fill the vessel, even though it really wants to float to the top.

Here is a very rough proof of concept.

[Note my poor neglected cluster siphon sitting in the bottom of the sink at the back right.]

What this means is that if you had a vessel with a hole at each end, and a floating ball inside, you could hold it up empty, and the ball would fall to the bottom and sit in the hole. Now if you fill it with water, the ball will stay down and allow the vessel to fill up. Or should do.

If this happens, the vessel could be balanced in such a way as to tip when it became full. This should be possible, because the ball at the bottom would displace more weight of water than the ball weighed. The vessel gets top heavy, and tips. It then empties out of the hole in the other end. As the water is emptying, the weight of the inflowing water maintains the commitment to spill water in that direction, and through that end. The ball comes away from the hole it was in, and floats around for a bit. If you stop adding water to the vessel, the water drains, and the floating ball now should sit in the hole at the other end of the vessel. When the water is turned back on, the operation repeats, but in the opposite direction.

Take 2 PVC pipes at 200mm length.
Add a T junction pointing up in the centre.
Cap the 2 ends and drill holes in the end caps that roughly match your water input (you could add taps)
Add a foam ball into the tube that is a bit smaller than the diameter of the pipe.
Add a mesh so the ball cant escape out of the top of the T junction, but water can still flow in.
make the device balance (roughly) at the T junction.

Now add water flow from your pump to the top of the T junction through the mesh. (you might need a simple overflow coming from a hole in each side of the section of T pipe that goes up, running parallel to the main pipe to make it so you can size the holes to keep the water level at roughly the T so the ball doesn't block the end too soon)

Every time you stop the pump for a few seconds, the device will drain, the ball will block the draining hole, and when the pump comes back on, the device will tip to spill water from the other side.

Approximate cost...    
 $2 - $5

Approximate coolness if it works...    

[edit from the future - There is some additional material on sequencers. Readers might find this newer version in a post titled  The Bullwinkle sequencer build of interest. It's a better design, and only costs around AU$15 to build with off the shelf PVC components]

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