Introduction: Arduino Controlled Seed Incubator

Why?

I bought a couple of Carolina Reaper chili seeds. The first batch was a failure only one seed germinated but it died.

So I ordered another 10 seeds, this time i'm a bit more prepared. I think previously they didn't germinate because the temperature was wrong and I started them just before summer when it was still a bit cold.

This incubator will keep the temperature around 29 degrees Celsius, between 28 and 30.

The circuit.
Its very basic all you need is a temperature sensor, Some nichrome heating wire which can be found in most fan heaters and hairdryers and offcoarse you will need an arduino.

Step 1: Building the Heating Pad

I used some vero board because it already has holes that are bigger than the thickness of the nichrome wire. All i did was "sew" the wire through the holes up and down until I populated the whole heating pad. Make some measurements before you jump in because you want the element to be around 10 ohms.

After you are done you can either mount the electronic components outside or directly on the board.
I chose to mount the components onto the veroboard because its using a LM7805 5v voltage regulater it also generate some heat which aids to bringing up the temperature inside the container.

After mounting ll of the components I used a bid of ferric chloride to eat away the copper strips on the board.
I should have etched the board before starting, but I didn't plan it through.

How the heating pad works electronically.

As said I'm using a LM7805 5v voltage regulator to bring the voltage down from 5V, You really don't need more than 5v the nichrome wire generates allot of heat, so much that it can turn red if the resistance is too low.

After the voltage was dropped to 5v I'm using the arduino to trigger a transistor IRL520 which is a 10A negative gate mosfet.

Step 2: Controling the Temperature

I bought a shield from my local Arduino supplier, which is based on the LM35 sensor and its very easy to use later int his instructable I show you the code.

The arduino monitor the temperature once it reached the desired temp, it will write a low state to digital output pin 8.
Once the temp dropped it will obviously then digital write High to pin 8.

Step 3: Wiring the Circuit

The circuit.

See the attached picture its pretty straight forward

Step 4: The Code

//initializes/defines the output pin of the LM35 temperature sensor
int outputpin= 0;

//this sets the ground pin to LOW and the input voltage pin to high

void setup()

{

pinMode(7, OUTPUT); pinMode(8, OUTPUT); //pinMode(13, OUTPUT); Serial.begin(9600);

}

//main loop

void loop() {

int rawvoltage= analogRead(outputpin);

float millivolts= (rawvoltage/1024.0) * 5000;

float celsius= millivolts/10;

if(celsius>=29)

{

digitalWrite(8, LOW);

digitalWrite(7, LOW);

//digitalWrite(13, LOW);

Serial.print("Heater Off TEMP:");

Serial.println(celsius);

}

else

{

digitalWrite(8, HIGH);

digitalWrite(7, HIGH);
//digitalWrite(13, HIGH);

Serial.print("Heater On TEMP:");
Serial.println(celsius); }

delay(1000);

}

Step 5: Watch a Build on YouTube

Comments

author
mviljoen2 (author)2016-08-28

I forgot to include the 10K resistor across the outer legs of the IRL520, Without it the transistor will erratically turn on and off.

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