Experimental Icubator – prototype “Mamut” build up 22/12/2013

•22/12/2013 • Leave a Comment

This and next few posts are about building a second generation of experimental incubator called “mamut” which will be presented under the Food Hacking Base logo at 30c3 in Hamburg. For credits please see “thank section” below, for sure Brmlab was great!

Please take this post as an opening, which will be later on detailed during the presentation at the event and workshop.

The basic idea is to build up again a device which will allow for easy control of internal conditions, in this case especially temperature, making fermentation of variety of culture and products much more easy and fun.

The project can be divided in several sections.

  • First the hard outer shall of the incubator chamber will be build made from plywood, insulated inner part will be done from polystyrene or PIR insulation boards (seams/gaps sealed by silicone and boards connected to plywood by same). Inner layer of the chamber will be done from some easy to wash material, at least for the bottom for the incubator chamber.
  • The heating/cooling and ventilation system will consist of peltier, most likely with help of H-bridge allowing to switch the polarity so both of them can cool and heat. The peltiers are likely to be TEC1-1270 (89W) each. To transfer the heat, heat-paste and , heat sinks (quite massive aluminium blogs) will be used and to remove/distribute the heat CPU coolers will be installed so ventilation sorted.
  • The brain and “sensoric apparatus” will be arduino based, temperature probes measuring inside temperature and based on readings switching on/off the peltiers and ventilators through solid state relays. More info you can find on the Techinc wiki at page managed by Arnd.
  • Many thanks to Brmlab for letting us to use their facilities and for all the help. Special thanks to “Santa”, Ray, Kyknos, Pasky and NiektO! For external help Arnd, Lars and Erwin has to be mentioned.

That is just a short introduction, this post will be updated and improved soon.

Sincerely,

Frantisek

DIY Dryer Prototype Build Up

•11/11/2013 • Leave a Comment

This simple project is an answer to our need here in Jeju island where we live to dry things mostly foods like mushrooms, herbs, fruits and algae when the weather is bad and sun is not around to help out (and during the rainy season when the humidity is incredibly high so everything goes moldy).

Because of my basic electronic skills the prototype is extremely simple and because of our tight budget very cheap. To summarize the basic idea: we use the heat source to warm up the air which naturally rises up and passes through the things which we desire to dry. To make this happen we decided to use a plywood wardrobe box as a chamber, standard 100 W light bulbs as a heat source, computer fan for removing the warm air later on from the box (connected to the appropriate traffo), usual electric switch and standard electric wires to wire it up, connecting it to the 220 V network and for the testing cheap hang out plastic drier. It is all very primitive, which was the goal so I  think anyone can do it.

Now bit more in detail what we used and how we did it.

  • Electronics

Equipment&Parts

3x light bulbs (100 W each)

3x light bulb sockets

2-3 m of electric wires (strong enough to carry +- 500 W)

1x electric switch

1x electric plug

1x tin solder

electrical  tape

extension cord – sockets

Tools needed

1x soldering iron

1x cutter

1x plier cutter

1x plier

1x saw

1x electric drill

  • How  the electronic part was done

The light bulb sockets had a loop wire attached to them, I’ve cut it in the middle, exposed the copper wire and twisted it around itself so it was consistent/compact. I cut the electric wire which I had extra (designed for heavy electric loads) and used each single core wire, unstripping it and attaching it to the bulb wire, keeping the colours same, to avoid the short circuit. When the wires were twisted around each other I’ve applied large quantities of solder on them to avoid separation later on and taped/covered each of this junctions by large amount of electric tape to insulate it properly. Once all the wires were attached to the light bulb sockets I’ve attached the wire which was to deliver the power in the middle section (close to the middle light bulb), again removing the insulation from it, twisting it around each other, applying solder and insulating it with the tape later on. In this case the power plug was already installed at the end of the wire. I’ve later on cut the power wire again, installing the electric switch, connecting the wires properly to it ???. When this was done I’ve screwed the light bulbs into the sockets and switch them on and off using the electric switch, making sure that all parts function.

The last part of the heat source setup was to make it stable. I’ve cut around 50 cm long 2×2 wooden bar and attached the light bulb apparatus to it, using partly stripped copper wires to make it tight (twisting the stripped part around each other) also drilling holes in the wood, one next to each light bulb, using second set of wires through it to stabilize the bulbs even more. It is not the best solution but it worked.

The ventilator was taken from a computer box and it is a usual computer fan. I’ve used 9 V traffo (power source, check picture) as a power source, again cutting the power cord and connecting the wires, testing before soldering if it works, soldering and insulating them later on. I’ve connected the traffo into the 220V power line making sure that the fan works fine.

  • Re-build of the box

Equipment&parts

2x wooden screws

Tools needed

1x electric drill

1x hammer

1x chisel

The plywood wardrobe was falling a bit apart but as a temporary solution it was sufficient. I’ve measured roughly and labeled by pencil where I want to make holes to allow the air into the chamber, plus the hole on the top of the box to install the fan taking the air out to complete the circulation. To make the holes I’ve used electric drill, drilling many holes around the diameter of the main hole and after that using the hammer I’ve knocked the plywood piece out, making it smoother later on with chisel. This I repeated for all four holes. I’ve installed the fan to the top hole in the box. I’ve drilled in two screws to the side of the box so I could hang out the drier on them.

  • Did it worked out?

Well the testing looks good so far. We’ve used a kombucha SCOBY which is a microcellulose fiber to see how quickly it is going to dry out. Starting weight was 286 g (7/11/2013), within 24 hours from switching the 3×100 W and fan on it went down to 145 g (8/11/2013), 53 g (48 hours, 9/11/2013) and 13 g after 72 hours (10/11/2013), when I finished the experiment. The structure of the SCOBY did not dried as I liked but that is not relevant in this case. The drier was running in 3×3 meter room, where we also installed the dehydrator, so the humidity of the air in the room was quite low, temperature between 23-26°C most of the time.

  • Things to improve

- the box should be made more sturdy because now it is unstable, alternatively whole new box should be constructed

- the heating element is not very stable, the light bulbs tend to slide on a side touching sometimes the plywood which is dangerous because they are quite hot, they need to be further stabilized

- temperature probe should be installed to monitor the temperature in the chamber, if possible connected to the microcontroller which would allow for switching the heat source on and off depending on the temperature in the chamber – for example switching off one or two light bulbs from the three

- drying racks should be constructed so the space in the chamber can be used more efficiently and also more appropriately based on what is suppose to be dried

- whole box should be made impermeable for the insect so especially the fruit flies can not get in spoiling the fruits or kombucha SCOBY’s with their larvas

- 3D model of the dryer should be made and posted to the blog

- electric circuit should be made as a scheme and posted to the blog

- if microcontroller is used later on, code should be uploaded and shared

  • Links

light bulb based  dryer – nice video which inspired me

Arduino Sketch 5/12/2012

•05/12/2012 • Leave a Comment

Below is, at least for now the final sketch for the experimental incubator including the temperature probe, heating and cooling unit. Many many thanks to Paek kwang woong (백광웅) for the development of both hardware and software. The prototype is currently running at Susubori Academy, the work on “new generation” is about to begin :-)

  • SKETCH

//TMP36 Pin Variables
int sensorPin = 3; //the analog pin the TMP36’s Vout (sense) pin is connected to
//the resolution is 10 mV / degree centigrade with a
//500 mV offset to allow for negative temperatures
/*
* setup() – this function runs once when you turn your Arduino on
* We initialize the serial connection with the computer
*/
void setup()
{
Serial.begin(9600); //Start the serial connection with the computer
//to view the result open the serial monitor
}
void loop() // run over and over again
{
//getting the voltage reading from the temperature sensor
int reading = analogRead(sensorPin);
// converting that reading to voltage, for 3.3v arduino use 3.3
float voltage = reading * 5.0;
voltage /= 1024.0;
// print out the voltage
Serial.print(voltage); Serial.println(” volts”);
// now print out the temperature
float temperatureC = (voltage – 0.5) * 100 ; //converting from 10 mv per degree wit 500 mV offset
//to degrees ((volatge – 500mV) times 100)
Serial.print(temperatureC); Serial.println(” degrees C”);
delay(2000); //waiting a second
}

Arduino sketch 29/8/2012

•29/08/2012 • Leave a Comment

Here is the arduino sketch which we use to control the prototype of the experimental incubator.

 

#include <LiquidCrystal.h>
String modeStr[]={“Set Min “, “Set Max “, “Current”};
int mode=2;
int maxTemp=25;
int minTemp=23;

const int downButtonPin=2;
const int upButtonPin=13;
const int onBoardTempPin=A1;
const int lineTempPin=A0;
const int heaterPin=9;
const int coolerPin=10;

boolean upButtonState=false;
boolean downButtonState=false;
boolean heaterState=false;
boolean coolerState=false;
LiquidCrystal lcd(12, 11, 7, 6, 5, 4);

int tempPin=0;
int tempPin2=1;
int onBoardTemp=0;
int lineTemp=0;

void setup() {
lcd.begin(8, 2);
//analogReference(INTERNAL);
attachInterrupt(1, set, FALLING);
pinMode(upButtonPin,INPUT);
pinMode(upButtonPin,INPUT);
pinMode(heaterPin, OUTPUT);
pinMode(coolerPin, OUTPUT);
}

void printStrLCD(int row, int col, String str)
{
lcd.setCursor(row, col);
lcd.print(str);
}
void loop() {
if(mode==2) //current Temp, minTemp, maxTemp
{
int midTemp= ((maxTemp*10) + (minTemp*10))/2;
onBoardTemp=0;
lineTemp=0;
for(int i=0; i<20; i++)
{
onBoardTemp+=map(analogRead(onBoardTempPin), 0, 930, 0, 1024);
lineTemp+=map(analogRead(lineTempPin), 0, 930, 0, 1024);
}
onBoardTemp/=20;
lineTemp/=20;
String topStr= String()+ (onBoardTemp/10) + “.”+ (onBoardTemp%10) + ” ” + maxTemp;
String bottomStr=String()+ (lineTemp/10) + “.”+ (lineTemp%10) + ” ” + minTemp;
if(!heaterState && lineTemp<minTemp)
{
heaterState=true;
coolerState=false;
digitalWrite(heaterPin, HIGH);
digitalWrite(coolerPin, LOW);
}
if(heaterState && lineTemp>midTemp)
{
heaterState=false;
digitalWrite(heaterPin, LOW);
}
if(!coolerState && lineTemp>maxTemp)
{
heaterState=false;
coolerState=true;
digitalWrite(heaterPin, LOW);
digitalWrite(coolerPin, HIGH);
}
if(coolerState && lineTemp<midTemp)
{
coolerState=false;
digitalWrite(coolerPin, LOW);
}
printStrLCD(0, 0, topStr);
printStrLCD(0, 1, bottomStr);
for(int i=0;i<1000;i++)
{
if(mode!=2)
break;
delay(1);
}
}

if(mode==1)
{
upButtonState=digitalRead(upButtonPin);
downButtonState=digitalRead(downButtonPin);
if(upButtonState==HIGH)
{
maxTemp+=1;
delay(300);
}
if(downButtonState==HIGH)
{
if(minTemp+1<maxTemp)
maxTemp-=1;
delay(300);
}
printStrLCD(0, 0, modeStr[1]);
String str=String()+maxTemp+”      “;
printStrLCD(0, 1, str);
}
if(mode==0)
{
upButtonState=digitalRead(upButtonPin);
downButtonState=digitalRead(downButtonPin);
if(upButtonState==HIGH)
{
if(minTemp+1<maxTemp)
minTemp+=1;
delay(300);
}
if(downButtonState==HIGH)
{
minTemp-=1;
delay(300);
}
printStrLCD(0, 0, modeStr[0]);
String str=String()+minTemp+”      “;
printStrLCD(0, 1, str);
}
}
void set()
{
switch(mode){
case 0: mode=1;
break;
case 1: mode=2;
break;
case 2: mode=0;
break;
}
}

 

Build up of heating and cooling unit 27/7/2012

•07/08/2012 • Leave a Comment

The heating/cooling unit (hcu) of the incubator is suppose to heat up the incubator chamber in a control way up to 50°C within 15-30 minutes and cool it down to 15°C within similar period of time. It was build up within a range of several days.

The computer power supply unit (PSU) producing 300 W ??? was used to power the hcu, fans etc. The central part of hcu consisted of aluminium based heat sink, dimensions 65 on ??? mm with five fins in parallel in the middle. This heat sink was insulated from outside by thin slice of insulation (what type???). Two peltier  modules were cleaned properly and thermal grease was applied on both sides of each of them. The 100 W peltier module was positioned on the left hand side of the heat sink, approximately in the middle with the heat generating side attached to the central heat sink. On the cold generating side of the peltier another aluminium heat sink with 21 fins and fan was attached. On the right side of the central heat sink 60 W peltier was attached again thermal grease applied on both sides. The cold generating side was attached to the central heat sink and heat generating side was attached to the aluminium based heat sink with fan, same dimensions as for the 100 w peltier. In both cases an insulation was cut out in the shape of peltier module so the module was directly attached to the heat sinks however around it, between the heat sings themsleves the insulation was places so the thermal exchange was minimised.
In order to keep whole hcu more stable, it was attached to the plywood desk (dimensions – 35 cm long; 13.5 cm broad and 3 mm thick). Everything was tight together with two plastic cable ties, making sure that all the heat sinks are in full contact with the peltier modules.

The hc unit was transferred on the top of the incubator. The PSU fan (dimensions 80x 80 mm) was used to move the air from the hcu to the incubator and back. It was placed directly in front of the hcu, blowing the air through the heat sink and secured to the plywood board by another cable tie. Cardboard and tape was used to create two enclosures to secure air tight circuit. One enclosure was placed before the fan and taped to the cardboard below and to the fan, it had approximately 10 cm long and 6.5 cm wide opening into the incubator chamber. Second enclosure was attached to the rear end of the central heat sink with approximately same size opening to the incubator chamber. Whole structure was taped by insulation tape and usual tape from both inside and outside to ensure that the circuit will be quite air tight and ready for testing.

Things to consider

The plywood used to secure the central heat sink should be removed so the heat sink is radiating heat directly in to the incubator chamber improving the heat transfer.

Completion of the incubator chamber

•01/08/2012 • Leave a Comment

The completion of the chamber was done on 10/6/2012 by attaching the doors to the chamber. I used two door hinges with three screws on both sides of the hinge, I believe 20 mm wooden screws. The hinges were located 15-20 cm from the top respectively bottom edge. The door bolts were connected by two wooden screws on each side (of the door and the chamber) and were adjustable due to the screw thread, see the pictures.

The top ventilation hole was enlarged so it was 12.5 cm wide and 35.5 cm long to accommodate the ventilation duct properly.

Last part which has to be done is the insulation between the doors and the incubator chamber. Temporarily cardboard was used approximately 3 cm wide and 55 cm long, thickness around 3 mm.

When tested the doors do not close properly but that should be improved once the proper insulation will be used. In the worst scenario another door hinges will be used.

The box was subject to testing when the heating and cooling unit was finished as reported in the next post.

The Construction of the Doors 9/6/2012

•09/06/2012 • Leave a Comment

The doors are going to be composed from external layer of MDF board (60×60 cm, 12 mm thickness), internal part made from polyethylene (PE) sheet (60×60 cm, 5 mm thickness), wooden frame (26 mm on 40 mm and to fit the 60 cm sides) surrounding insulation layer from polystyrene (44 mm thickness). The overall thickness of the doors is around 65 mm, elastic plastic material was used to fit between the PE and wooden layers. Silicone was applied so whole structure was sealed.

Procedure

- the wooden frame was measured and cut with two pieces being the 60 cm and two to fit eatch the 60 cm edge
– 10-15 mm deep holes were drilled (3 mm drill) into the wood and brackets (smaller size, one screw at each side) were attached by 28 mm “wood” screws
– holes were drilled (3 mm drill) through the MDF and partly to the wood and 28 mm “wood” screws were used to connect the wood and MDF; location of holes – 12 mm from one edge and 20 mm from the other in each corner and again 12 mm and 300 mm (center of the side)
– silicone was applied into the seal between MDF and wood on the internal side
– polystyrene board (44 mm thickness) was partly cut in corners to fit and slide in
– the elastic plastic material (2.6-2.7 mm) was cut into strips to fit between the PE, MDF and polystyrene, two layers used
– the strips of elastic material were put into position and PE sheet was placed on the top and holes were drilled by 3 mm drill through all the way to the wood (some 4 mm in it); location of holes: 12 mm from the edge and 5 per each side
– silicon was applied between the wood and elastic material and elastic material and PE sheet
– the 28 mm “wooden” screws were used to attach quickly the PE sheet to the wooden frame
– notes and photos were taken the doors were left to dry

 
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