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RibbonFish Proof-of-Concept

Using the principle of Agile development, we are building a quick-dirty proof-of-concept codenamed RibbonFish.

The RibbonFish is a low-temperature (less than 100C) model consisting of two heating cloths and 12V fan, controlled with three simple thermocouples. Although weak compared to the goal-product, this allows us to exercise much of the functionality that we will eventually need.

Hardware Choices

Because the RibbonFish is a real machine, it forces us to make hardware pin choices for the Arduino to control the 6 hardware electronic devices. These choices are documented here to allow duplication of the device; the hardware choices (GPIO pins) must match the software configuration.

  1. The thermocouples are DS18B20 Temperatures sensors purchased from Adafruit, and configured using the OneWire digial protocal We use Digial Pin 2 as the signal pin for this.
  2. The Fan and Heaters #1 and #2 are controlled via PWM (ranging from 0-12V.) The pins are: Fan = PIN 3, Heater #1 (Preheater) = PIN 4, Heater #2 (stack simulation) = PIN 5

The Fan is a simple DC 12 Vote Fan that fits inside a 4" PVC pipe. The heaters are Adafruit 4" x 5" heating cloths, around 1 ohm each.

Note: We do not believe an unfiltered PWM signal is appropriate for the actual chemical stacks due to internal chemistry, or at least this has not yet been tested. However, as a prelude to a real system, PWM can be used with the heating cloth using simple power transistors.

Photo of the RibbonFish

The Ribbon Fish consists of a PVC vent fan (12V, inline) connected via a heavy paper cone to piece of 3/4" PVC piping. There are 3 such pipe sgements, each about 16mm long. These each have a 1/4" hole for the temeperature sensor in the middle. In the two joints between the three pipes, a heating cloth is rolled up into a cylinder and inserted into both pipes. The leads are exposed to power the heating cloths.

IMG-2837

Libraries

PlatformIO provides useful package and configuration management, but it still requires thought and documentation.

We believe teh DS18B20 thermometers require these libraries

pio lib install paulstoffregen/OneWire pio lib install milesburton/DallasTemperature

Simple Commands for the RibbonFish

In order to continue moving to more versimilitude, we need to implement a serial-port based command structure within the RibbonFish. Without being ready to specify everything, let me describe a few commands.

Parameter Commands

The first commands for the Ribbon Fish are:

  1. W - Warmup
  2. C - Cool Down
  3. Set exhuast temperature than (first or second) heater
  4. Set the speed of the fan

The command set the target temperatures for the first and second heater

{ "com": "T",
  "par": 0,
  "mod": "T",
  "val" : 34.3
  }
{ "com": "T",
  "par": 1,
  "mod": "T",
  "val" : 36.0
  }

This command says enter the cool down mode:

{ "com": "C",
  "par": 0,
  "mod": "U",
  "val" : 0.0
  }

This command says enter the warm up mode:

{ "com": "W",
  "par": 0,
  "mod": "U",
  "val" : 0.0
  }