Two solenoids control the flow of the nutrient solution: A spray solenoid between the pressure tank and misting loop that is turned on when it's time to spray, and a multi-purpose bypass solenoid that instantly releases pressure from the misting loop to stop spraying. It also helps to bleed air from the pump by de-pressurizing the pump's discharge side and circulating the nutrient solution back into the tote until air bubbles leave the tubing.
Table of contents
Before getting started on the assembly first we must learn how to pressure seal threads using the “yellow” Teflon tape designed for gas, water, and oil lines. The yellow version has a double density (1.5g /cm3) capable of creating a seal up to 20 bars. Depending on how tight the threads are apply 5-10 rounds of tape to create a seal. You will need fewer rounds when sealing plastic to plastic threads (4-6 rounds) compared to metal to plastic or metal to metal fittings (7-10 rounds). Here is a Youtube video on how to apply Teflon tape. Note: There is no need to apply Teflon tape where components are interconnected with a washing machine hose, they have a rubber gasket to create the seal.
Sealing metal threads
7-10 rounds of Teflon tape
Sealing plastic threads
4-6 rounds of Teflon tapeThe spray and bypass solenoids are attached to an assembly made from 3/4" threaded parts with two inputs and two outputs:
Top right input: Spray intake with a fine metal mesh filter connected to the pressure tank's spray output. This intake is always pressurized and the spray solenoid controls the flow into the Misting outlet.
Top center output: Misting outlet connected to the Misting loop inside the aeroponics tote. A check valve connects the misting outlet to the bypass side, creating a path to quickly release the pressure from the misting loop at the end of the spray cycle by opening the bypass valve. The one-way valve also prevents water from flowing back from the bypass side to the misting loop while the pump is self-priming / refilling the tank.
Top left input: Bypass intake connected to the pressure tank's bypass output, creating an alternative path for the diaphragm pump's output when the Bypass solenoid is open. This is needed to remove air pockets from the circuit while the pump is self-priming and also used to circulate the nutrient reservoir. A check valve on the intake is preventing reverse flow while the spray solenoid is active.
Bottom output: Bypass outlet feeding back into the reservoir. Connects to a 3/4" bulkhead fitting at the bottom of the aeroponics tote.
The assembly is mounted to the side of the aeroponics tote. Starting from the right side we have the fine metal mesh filter connected to the pressure tank's Spray output, spray solenoid controlling the flow, Tee fitting that connects the misting loop, one-way valve, Tee fitting connecting the bypass solenoid, and finally another one-way valve connecting the tank's Bypass output:
Water filter
40-micron filter, 3/4" intake/outlet1/4" connector at the bottomMax 8 bar / 125 psi
Pressure sensor
1 pcs, 5V power, 1/4" external threadPressure: 0 - 1.2 MPa (Max 12 bar / 174 PSI)
Washing machine hose
3 pcs - 1.2 meter / 4 feet3/4" internal thread
