Irrigation

In this chapter, we are going to build the irrigation system for the Hempy buckets where watering is controlled by the Hempy module based on the weight of the buckets or by a timer. This setup consists of the following components:

External nutrient reservoir on a rolling weight platform, monitored by the Reservoir module
Air pump and air stone for keeping the nutrient mix fresh
Dedicated self-priming pumps for each Hempy bucket
Four irrigation stakes / Hempy bucket
Dedicated waste reservoirs for each Hempy bucket Not needed anymore, the drained water is calculated using the bucket's weight sensor

SketchUp 3D Warehouse: Gbox420 - ShowRoom

Or visit the Gbox420 GitHub page and download the entire project.

Nutrient reservoir

Any food-grade high-density polyethylene (HDPE) container should do as long as it's lightproof to prevent algae growth. Try to find a barrel with a lever-locking or snap-on lid as it is super annoying to twist off the lid once the sensors, water, and air hose are installed. Size the reservoir according to the plant’s daily maximum water requirement multiplied by the number of days the reservoir should last ( I aimed at ~4 weeks with an average usage of 1 liter/plant/day or 1/4 gallon/plant/day and got a 60L/15 gal. barrel)

Barrel

60 liter / 15 gallonFood grade

Amazon.com, Amazon.de

Plastic tubing

7.5 meters / 25 feet, Non transparent8mm / 5/16 ″" internal Ø

Amazon.com, Amazon.de

Line manifold

4 way, With control valve5/16" Ø main connector, 3/16” Ø outlets

Amazon.com, Amazon.de

Holes on the lid:

Waterline to the pumps: Slightly larger hole than the water hose diameter for easy removal
Temperature sensor: Shares the same hole as the water line
Hose for the air stone: Dedicated 4mm - 1/8" hole for a single air stone. (I had a dual outlet air pump, but a single outlet pump should do fine)
pH sensor: Requires the largest hole on the lid to fit the probe body through. - As you guys pointed out: Keeping the pH probe in the reservoir continuously is NOT recommended as it reduces the lifespan of the probe. I'm planning to add a small external pH probing container with two bi-directional dosing pumps to either fill the container with a probe storage solution or a sample of the reservoir.

Lid with the waterline and temperature sensor routed through it

Reservoir module + Air pump on top of the reservoir

Rolling weight platform

To monitor the amount of nutrient solution remaining in the reservoir I built a weight platform for it. As I did not want to break my back lifting a 60 liter / 15 gallon container full of water I added a second platform with caster wheels below the weight platform. The plans are available under the Sketchup Showroom - Rolling Platform section.

The rolling platform is the same size as the weight platform and has four stop blocks on each edge to hold the weight platform in place. The stop blocks are mounted from the bottom using two pocket holes and they have 2 metal shims between the platform and the stop block to allow the weight platform to drop in from the top unrestricted.
Note: Use marine plywood for the platforms as it is a lot more rigid than the pine boards I have used.

Water pumps

Each Hempy bucket has a dedicated 12V - 2A diaphragm pump mounted under them. The pumps are controlled by the Hempy module based on the weight of the buckets.
Before mounting the pumps under the Hempy buckets we need to disassemble them do the following steps:

Make sure the pump head and bearing have plenty of grease. Some manufacturers ship the pumps without any lubrication.
Install noise filtering capacitors and a voltage spike removing fly-back diode
Install a waterproof DC connector

Disassembly is pretty easy, the entire assembly is held together by two screws / pump:

As the first step we need to solder the following components:

Schottky diode across the positive and negative terminal with the white mark (Cathode side) facing the positive terminal. I used a 1N5822 diode rated for 3A forward current with 40V reverse voltage. You can use any other Schottky diode as long as it can handle 2A forward current and have at least 25V blocking voltage. Check out this Electronics Hub article to understand why flyback diodes are a crucial part of DC motors.
Ceramic capacitor (100nF - Number 104 ) between:
- positive terminal and motor housing
- negative terminal and motor housing
- positive and negative terminal

To find out more about the noise suppressing capacitors at Pololu.

Next route the female end of a waterproof DC power connector through a hole drilled in the plastic motor case. Use a small cable tie at the very end of the cable to prevent it from sliding back out. Solder the red wire to the positive terminal of the motor and the black to the negative.

Apply a generous amount of grease to the motor bearing and inside the pump head, then fit the motor back to its housing and reattach the pump head. Make sure to check the flow direction arrow on the pump head and assemble the second pump in the opposite direction (Rotated 180°) as the first one. This will be important when mounting the pumps.

Mount the pumps at the bottom side of the Weight platforms in a way that the intake sides face the back of the Hempy buckets. Connect both pump's intake using an 8 mm internal diameter hose to an 8 mm Tee fitting. Connect the third side of the Tee fitting to the tube coming from the reservoir.
The output side of the pumps will be connected to the Line manifold installed at the edge of each Hempy bucket in the next section.