Overview of function
- Disposable cuvettes (pre-filled with reagent) are placed in a rotating carousel
- At sampling time, (whether this is the same day, next day, 7 days later etc.) the cuvette with reagent is moved to the pump and filled with 3mL of filtered bioreactor media sample (and distilled water if a dilution is necessary),
- Cuvette is next rotated to a "stir-plate" position for mixing of the reagent
- Cuvette is finally moved to the colorimeter "measurement" position (led/sensor pair).
Overview of design
- Pumps: two piezoelectric pumps. One for dispensing filtered algae media, the second distilled water for dilutions.
- Fluid weight sensor: A 20g micro load-cell will be used determine fluid dispensed and this data will used to control the pumps.
- Carousel design for moving cuvettes from pumps to colorimeter. Stepper motor.
- Magnetic stirring: mixes reagents and sample for accurate color development
- Reagents: Cuvettes are pre-loaded with powder or liquid reagent. For now this version will mean that tests are limited to only one reagent but in future can investigate tests with two or more reagent steps. Cuvettes have caps with a small hole for liquid from the pump plus a micro stir-bar.
- Home position set using a photogate (beam-break) sensor
- Control: Custopm PCB and Arduino Mega
Overview of control tasks
- Control stepper motor to carousel
- Read home switch (photogate)
- Read colorimeter
- Switch on/off stir-motor
- Read fluid weight from load cell
- Control pumps
- Control servo motor for tipping fluid into cuvette