Prototype proposal

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Experimental Incubator (ei) - Project Proposal 20/5/2012


Experimental incubator is a device designated to control it’s internal conditions. The prototype is going to allow for a temperature regulation both at constant level and more importantly for controlled temperature oscillation. Another factor included is monitoring of it’s electricity consumption. The temperature is a crucial factor in food&beverage fermentations therefore device which is optimized for these purposes is needed. The novelty temperature oscillation function allows to optimize the growing conditions for cultures comprised from multiple microorganisms with wide range of temperature optimas. Next generations will be more sophisticated aiming for measurement and control of CO2, oxygen levels, stirring, humidity etc. The device will be build to comply with principles of low energy consumption, easy to repair and upgradeable structures, sturdiness in accordance with concept of environmentally friendliness. This project is based on an open source aiming to bring this tool to as many brewers and fermenters being as affordable as possible.

Key Words: experimental incubator; temperature regulation; temperature oscillation; measurement of electricity consumption; upgradable; environmentally friendly; open source; brewing; fermentations.

First prototype of ei. presented at Maker Fair 2-3/6/2012

  • Functions

- temperature monitoring

- temperature control - setting up a constant level and allowing for controlled temperature oscillations

- electricity power consumption

The design

The incubator will consist of two separable parts,

  • the box - respective incubator chamber composed from three layers - outer protective, middle insulational and internal protective and insulated doors
  • central unit - arduino clone based microcontroller with display and manual control, peltier heating and cooling element with adjacent heat sinks and ventilation system

The Box Construction

Dimensions and materials

  • External Protective Layer

dimensions - cube: a= 610-710 mm; thickness = 7-13 mm

material - MDF board

cost - $30-40

  • Middle Insulation Layer

dimensions - thickness a = 50-70 mm

material - polyurethane foam or extruded expanded polystyrene (XPS) high density

cost - $20 - 30

  • Internal Protective Layer

dimensions - cube - a=500 mm; material thickness = 5-10 mm

material - high-density polyethylene (HDPE) sheets or polyvinyl chloride (PVC) sheets.

cost - $50-60

  • Additional materials for the box construction

silicon or glue - cost = $2-4

brackets (to connect the MDF boards) - cost = $3-5

doors - door hinge - cost = $2-3; door bolt (magnetic) - cost = $5-6

ventilation duct - cost = $???

brackets for the ventilation duct - cost = ???

The Central Unit Construction

This is a part which is not clearly designed and any help is highly appreciated!

Dimensions and materials

  • External Protective Layer

dimensions - cuboid: a= 400 mm; b = 400 mm; c = 300 mm; layer thickness = 7-13 mm

material - MDF board

cost - $15-20

  • Internal layer

There is probably no need to have additional internal insulation layer because of the ventilation system requirements. Or should be the internal cooling and heating unit with the fan system insulated??? If so how and how much???

  • Electronic components

microcontroller: ATMEL 90USB1286-AU; power requirements - ??? W; cost = donated; otherwise = ???

display: LCD display; power requirements - ??? W; cost = $10-15

manual control - numeric keyboard ???; power requirements - ???; cost = $???

temperature sensor: thermistor - type ???; power requirements; cost - $1-2

combined heating and cooling unit: peltier module (12 V 60 W); power requirements - 60 W; cost = $10-20

heatsink: aluminum alloy or copper based; dimensions - cooling smaller (3x4cm), heating bigger (7x10cm), details ???; cost = $10-15 (hot) and $5-10 (cold)

fans: 2 x 60 mm; power requirements - up to 2-4 W; cost = $2-3 (price and power consumption per each fan)

power source: 120-150 W; cost = $10-15

another electronic components:breadboard; relays; resistors; diodes etc. cost = $15-30

List of components and materials
Component/material Quantity Final price in US$
MDF board (1220x2440mm) 2 30-40
insulation foam 1 20-30
PVC or HDPE 50-60
silicon 1 2-4
glue 1 2-4
brackets (for MDF boards) 3-5
ventilation duct
brackets (for ventilation)
ATMEL 90USB1286-AU microcontroller 1
LCD display 1 10-15
thermistors 1-2
peltier module (30-60 W) 1
heatsink (smaller 3-4 cm) 1 5-10
heatsink (large 7-10 cm) 1 10-15
fan (60 mm) 2 2-3
insulation layer (between heatsinks) 1

  • Things to discuss concerning the design of the control unit and it's heating/cooling system controlled by microcontroller.

How to “close up” the ventilation duct to the chamber so the insulation is complete???

How to “switch” the warm or cold air circulation to the incubator and out???

The Code

This section is about developing the code to allow the arduino microcontroller to control and run the incubator as desired. The basic info for the first steps is here and it will be updated as we progress. The major focus for now will be on measurement of temperature and controlling it by peltier element.

What needs to be done:

  • 1. temperature measurement by thermistor

- temperature needs to be measured by thermistor (10 kohm)

- frequency should be +- every 3-5 minutes (if the heating/cooling phase is not on, than measure every 30-60 seconds)

- report/print the temperature so it is human readable (serial monitor?)

  • 2. switching on and off the peltier device based on temperature readings

- the peltier is 100 W so it will have power source to power it (around 250 W)

- switch the peltier relay based system on/off by arduino based on temperature reading (more below)

  • 3. switching on and off the fans to circulate the air from peltier to the incubator chamber

- the fans may have to use the power source/relay circuit too or it may be possible to power them through arduino directly not sure about that yet (small 2x 80-40 mm fans)

- once the peltier is switched on (based on temperature reading) the fan/s has to switch on (does the fan by the heat sink has to be always switched on???)

- each fan is pointed to the hot respectively cold heat sink with separated air ventilation systems/ducts to the chamber and out

- the peltier and fans should go a bit "over the desired temperature/overshoot" like a degree or two so they do not switch on/off all the time

- once the peltier is on the temperature measurement should be performed every 30-60 seconds

Well that would be a basic info, if you could have a look on it and please post on Tastebridge discuss or send email to Frantisek Algoldor Apfelbeck and it will be explained in more detail what needs to be, thanks a lot!

Here is a very simple example of what we need:

Constant temperature 25°C mode

Goal - keep the temperature of the incubator constant at 25°C +- 1 one degree


- measure the temperature every 3-5 minutes and display it (serial monitor)

- if temperature differs from desired

- switch on the peltier

- switch on the fan by - heat sink (to warm up) or - cold sink (cool down)

- increase the temperature measurement to frequency once per 30-60 seconds

- switch off the peltier once desired temperature is reached (with one degree over shoot)

- switch to the one per 3-5 minutes temperature measurement and display it (serial monitor)


Materials, literature and Interesting links

Peltier element

commercial cooler hacking - this is a video from Dave Jones where he is checking closely and hacking commercial version of peltier based incubator for reptile eggs

cooler kit test- short youtube video about how to test a cooling kit ordered from ebay based on peltier device, heatsink and fan

Links to tools for sharing and collaboration

Pirate Pad

Personal tools