Friday, June 28, 2013

Keeping it moving

The closed loop system
I spent weeks debating whether the tank should be plumbed with a closed-loop system. A closed loop would provide water movement while keeping unattractive pumps and wiring out of the display, but committing to fixed output locations was intimidating - once the output bulkheads were drilled, there would be no going back. In the end, the desire for an aesthetic display tank with concealed equipment won out over the desire for design flexibility down the road. Besides, I can always add powerheads later to complement the closed loop.

The original closed loop design called for locating both the pump and the water distribution device beneath the display tank. With that design, it would have been necessary to include even more bulkheads in the bottom panel of the tank within the confines of the overflow box. Eventually, I realized that I could plumb the pump in the stand, and the distribution device in the canopy, with only two additional bulkheads in the floor of the overflow. This design is illustrated in the rendered image, above.

Two 1.5" bulkheads (protected by spa intake covers) on the center line of the tank will be plumbed to the intake of a controllable DC pump, which will be plumbed in turn to a water distribution device. Originally, I planned on using an OceansMotions diverter, which relies on a high-torque, low speed motor turning a drum to distribute water among its four outputs in a cyclic fashion. But then derKroon Mechanics announced their new FlowWolf, which uses a high-speed stepper motor to distribute water among its four outputs in a programmable, or even pseudo-random fashion. The desire to have computer control over every aspect of the system was too strong to ignore, so the derKroon it will be. The distribution device is plumed to four bulkheads located in the angled walls of the trapezoidal overflow, to hopefully generate some turbulent whole-tank current.

According to the engineers at derKroon, the FlowWolf uses an Atmel AVR 324 in its proprietary controller, so it should theoretically be possible to connect the distributor to / control it from a Reef Angel controller. I look forward to the challenge of getting these two devices to communicate.