[FEATURE] - Aeroponics Solution Dosage

[nchareunsouk]

@JLefebvre55

Completion is tracked in the linked PR.

Design Scope

Design a solution dosage system for the addition of pH balancing solutions and nutrient solutions.

Purpose

The purpose of the solution dosage system is to add precise proportions of concentrates to the pressurized aeroponics line.

Function

Inputs:

• Flow rate
• Dosage ON/OFF and rate (per concentrate)

Outputs:

• Precise amounts of concentrates (proportionate to solution flow)

It interfaces with/depends on the following systems:

• Power
• Automation

System operation assumes:

• Line under pressure (80PSI)

Method

Options:

1. Venturi siphon injection: Too many unknowns, not enough pressure difference across the venturi, not directly controllable
2. Proportional flow solenoid valve (i.e. open for 5 seconds every minute) - hard to source and expensive.
3. Pre-mixing
4. Proportional injectors (piston-driven)
5. Peristaltic pump manifold: "Flow source" topology, rated for >80PSI back-pressure, "locked" when off, no backflow

Setup:

1. Connect pump lines to concentrate tank and manifold tee
2. Prime pump (automated; known priming time i.e. >= 5sec)

Process:

1. Primed pump is a "flow source" rated for operating back-pressure
2. Control flow of concentrates into solution line (0-12V PWM)

Shutdown:

1. Disconnect from concentrate tank and manifold

Features

Each feature should be added to relevant BoMs and CADs where applicable. Design decisions should be well-supported using relevant research and calculations, and should be documented in the Solution Overview. If a feature is complex enough, create a new issue for it using this template, and tag it here.

• Peristaltic Pump: PWM-controllable DC motor (i.e. 12V), rated for >100PSI, precise dosage
  • Pump Line: Soft (<70A Durometer) high-pressure (>100PSI) tubing, water-safe, probably like 3/16" OD silicone, for peristalsis operation
• Pump Line to Tank/Manifold Lines Adapter
• Peristaltic Pump Driver Board: Just PWM-able MOSFETs (faster switching, higher throughput than BJT)
• Concentrates Tank
  • Concentrates Tank to Pump Line Connector
• Flow Rate Sensor

Requirements and Validation

What does this design need to accomplish? How do we know it has accomplished this?

List any applicable metrics with criteria/constraints, applicable to purpose, function, method, and each feature, as well as how to test them.

1. TBA

Verification

Each test should be performed and documented, and the testing documentation attached to the PR. The testing suite should address the full scope of the function (i.e. ensure inputs are met and outputs work), method (all steps execute correctly), and features (each feature performs as expected) with respect to the purpose and requirements.

How does this design achieve its method effectively, safely, and reliably? How do we test this?

Specific testing procedure:

1. Max Dosage Rate - ???
2. Dosage Rate Precision @ Different Amounts
3. Dosage Rate Stability @ Different Rates
4. Backflow in OFF state, ON state at operating pressure

[JLefebvre55]

Siphons have:

• Input: 3/4" hose female
• Output: 3/4" hose male
• Inlet: Fits 1/4" OD tube (with some effort)
• Spring-based check valve

[JLefebvre55]

Todo:

• [DESIGN] - Peristaltic Pump #125
• Choose Flow Sensor YF-B1
  • Determine maximum flow rate, needed precision
• Design Pump Driver Board
  • Choose Transistor MMBT2222AT-7-F
  • Design
  • Order
• Write pump control software
  • Flow sensor reading
  • Actuator, instruction matrix entry
  • Unit tests
• Assemble and Test
• Update documentation
  • Solution overview
  • Plumbing diagram
  • BoMs
  • CAD

Background

TBA