Peterphrastus

Summer is short here in Canada. It is time to get ready for the next growing season. For 2009/2010, there will be four growing units:

• a seedling ebb and flow unit;
• a three pot HydroHomeSoft growing tray;
• a homemade 6” PVC pipe aeroponics unit; and
• two General Hydroponics Rainforest™ 66 units

While there are four units, there will be three channels managed by HHS. The aeroponics and Rainforest units will be hydraulically connected. Nutrient in these units will be circulated with a small pump. Nutrient will flow from the aeroponics reservoir to the front Rainforest unit, the rear Rainforest unit, the pH and EC sampling chamber and, finally, back to the aeroponics reservoir. The design flow is for forty minutes system latency.

The Rainforest grommets are replaced with thru-wall connectors and the units joined with a short piece of rubber tubing. Clamps ensure a leak-proof fit. Large connectors and 1 ¼” pipe ensures that the flow can be accommodated without a head buildup in the first Rainforest unit. Buildup could cause erratic float switch operation and slow down mixing time

Next, the rear Rainforest unit has a thru-wall installed on the side. Installing it above the ridges in the bottom of the unit will allow it to be positioned at a good distance from the inlet. This plus an airstone positioned under the inlet will ensure adequate nutrient mixing is achieved. The new thru-wall is joined to a thru-wall at the bottom of sampling chamber. Connection is made with 1 ¼” flexible pipe. The casting ridges on the thru-wall connectors need to be carefully sanded smooth and two layers of Teflon tape applied before the pipe and clamps are assembled.

The sampling chamber is connected to the aeroponics reservoir in the same manner. The thru-wall for this connection is at the top of the sampling chamber. It is positioned such that the nutrient level just fills the connector pipe. This level in the sampling container should be about one inch below the top.

Probes for pH and EC are fitted into the top of the sampling container lid. Drill holes that snug fit the probes to be used. Position the EC probe in front of the thru-wall at the top of the sampling container. The flow will help keep the EC probe clean. Fit the pH probe to the left of the EC probe. In the picture, only the EC probe is shown installed. This sampling chamber has a convenient flap at one end that can be used to independently check pH and EC calibration. This will be helpful for knowing when to re-calibrate.

The clear tubing from the aeroponics reservoir to the front Rainforest is the output of the circulation pump installed in the aeroponics reservoir. This tubing and the flexible white tubing will be wrapped with foil to prevent algae formation. Alternatively, black pipe and tubing could be used if available. I try to avoid anything that can absorb heat if possible. The circulation pump is a Laguna 1 which is only 6.5 watt. This should not cause excessive heating of the nutrient.

The float switch is installed on the front Rainforest unit. It can be adjusted as necessary to the desired nutrient level. In this setup, the level is approximately 9 ½ inches. Maximum air roots is the objective.

The aeroponics unit was constructed with one of the many plans available on the net. Since there are many detailed DIY aeroponics plans this will not be described here. One aspect that is important is the pump capacity. To achieve reasonably small droplet sizes, a 1/6 HP Little Giant sump pump is being used. A 100 micron filter is fitted to the pump outlet and is easily accessible for cleaning. The pump for the aeroponics unit and the vortex sprayers for the Rainforest units will be on a one minute on fifteen minute off cycle during the light period. Three equally spaced one minute periods will be used for the dark period.

The seedling ebb and flow unit will be connected to HHS this year to make sure the nutrient is refreshed and maintained at the right level. Last time it was not and the nutrients dropped too low a couple of times.

In total, HHS will have three channels. The solenoids are mounted such that a good gravity flow is achieved for each channel. The input for the aeroponics and Rainforests is the aeroponics reservoir. This is the longest path to the sampling chamber and will, therefore, result in the best average readings being obtained.

The complete setup is ready to go. Seeds will be started mid to late August and should be in the units by mid September. All systems have been tested with HHS to be sure the intermittent pumping does not promote erratic float readings. Still, a hysteresis of one minute for the floats is not a bad idea.