Build an Automatic Egg Incubator

Homemade Incubator - CircuitLib
Homemade Incubator - CircuitLibHomemade Incubator - Front panelMy homemade Egg Incubator
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We hope that this article will help you to build your own Egg Incubator, to incubate and brood small numbers of chicks. With some minor modifications, the proposed automatic egg incubator can be also used for other commonly incubated poultry and game bird species. 

Author: G. Adamidis

Creative Commons License
Tutorial on how to build an Automatic Egg Incubator by George Adamidis is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

Introduction

An incubator is an enclosure having controlled temperature, humidity, and ventilation.

Hatching eggs need to be kept at the right temperature and humidity, as well as need to be turned at regular intervals to stop the developing embryos from sticking to the inside of the shell. An automatic incubator turns eggs automatically, usually by slowly rocking them backward and forwards continuously.

Hatching EggsBuilding an automatic incubator consists of three main parts. The first part is the enclosure. The enclosure must have good physical properties, to ensure good thermal isolation between the interior room of the incubator and the external environment. The second part is the electronic equipment used to measure and control temperature and humidity. The last part is the device used for automatic egg turning.

Our incubator was designed to incubate 42 eggs each time. The dimension of incubator cabinet is 50×50×50cm. Walls made from plywood and were covered inside and outside with acrylic paint. Within the incubator cabinet, the temperature is kept at 37.6°C. In our experiments, humidity was adjusted within 60%-90% RH, using two, and separate water pans. One, 100W silicon heating cable, approximately 8 meters long & supplied with clips on wire ends, was selected as the main heating source. We have also included two sockets for incandescent lamps, to be used as backup heating elements. These sockets are powered together with the main heating element. Normally, the sockets are kept empty. However, in case of emergency, two 40W incandescent lamps can be placed on them to replace the main heating element.

Inside cabinet, two little fans were installed near the top wall to provide stable air circulation. For controlling and measuring temperature and humidity, we use the Humidity and Temperature Sensor Demo board, which is based on the PIC18F2620 microcontroller and the SHT21 sensor from Sensirion. For automatic egg turning, we use a common egg turner for incubators.

After performing 10 incubation experiments on chicken eggs, we have noticed that our incubator has an average hatch rate of about 84%. That is about 35 hatched eggs, of 42 eggs in total. Experiments performed on fertile eggs, ordered from poultry farmers having roosters in their flocks.


Building the incubator

The enclosure

The first step for making the incubator is to build the enclosure. The enclosure must have good thermal isolation properties to keep the eggs warm and the temperature constant in all parts of the incubator. Wood is a good choice as long as it can be kept clean and free of moisture. In our incubator, we use a 50×50×50cm cabinet, made from 1.9cm thick Marine Grade Plywood sheet. Marine grade plywood has good moisture resistance. However, for adding some extra moisture protection, we have covered the wood with three layers of acrylic paint. Covering the wood with paint is essential not only for moisture protection but for ease of cleaning also. You may not be thinking about this right now but when you come to clean your incubator after the hatch and see the mess that is made you'll be pleased you considered adding some layers of paint.Cleaning and sterilization between hatches is essential, since bacteria multiply incredibly quickly at incubation temperatures, and it doesn't take much for your eggs to go bad and even explode leaving a mess and even more bacteria over your remaining good eggs.

Homemade incubator enclosureFor making the cleaning process easier and for adding some extra thermal isolation, we decided also to cover the floor surface with a 3cm thick Styrofoam sheet. Covering all the walls with Styrofoam sheets would be a better choice but not necessary since the eggs will be mostly closer to the floor.

After building the enclosure, you must drill three holes at the rear wall of the incubator, of about 12mm in diameter, equally spaced at about 30cm above the floor, to ensure that clean and healthy air will be always reaching the cabinet. Incubators need to ventilate to allow enough oxygen to come in and to allow the produced carbon dioxide and evaporated water to escape.

It is obvious that the cabinet must also have a door. In our prototype, we use a door in front. Actually, the entire front wall, except for a small section near the roof, is used as a door. The front door is made from marine plywood and we use two barrel hinges to connect it to the rest of the enclosure. We also use two magnets, to ensure proper sealing. Above the door, we have built a small window. The window is made from a transparent sheet of plexiglass, placed on a large enough slot. The interior surface of the door is covered with a 3cm thick Styrofoam sheet, as the floor does too.


Adding fans

There are 2 main types of incubators: Still air and forced air. The difference is simply one or more fans. In forced air incubators, fans are used to circulate the air around the incubator to keep the temperature constant at all places.

Fans on Forced-air Incubator

Our incubator is based upon the forced air concept, and we use two small fans, placed near the top wall to ensure uniform air flow and heat spread. The fans are pointing downwards and there is a good explanation for that: Heat on air, always tends to travel upwards, and this is because warm air is less dense than cool air. Forcing top air layers to move downwards, has the effect of re-spreading heat which otherwise would tend to concentrate near the roof.

In the prototype, we use common 12VDC, 1.2W, 40x40x10mm, brushless fans, similar to those found on PC hardware. These fans run quietly and with very little vibration. We bought them from a local hardware store for about 5$ each.

The fans are placed parallel to the top wall surface, and symmetrically around the central point of the wall. They are placed towards the front-back direction, having a distance of about 20cm between them. They are pointing downwards (air flows downwards, from the roof to the floor) and they are also placed at a distance of about 4-5cm away from the interior surface of the top wall. Fans are always kept on during incubation.


Placing the heating cable 

Heating cable on incubator

The main heating element in our incubator is a 100W silicon heating cable, approximately 8 meters long. The cable is powered directly from the public power network. It is switched on and off from a solid state relay which is controlled from the Humidity and Temperature Sensor Demo board.

The heating cable is placed on the interior surfaces of the sidewalls and the top wall, holding the perimeter around the eggs. The cable is kept in place by some cable holding clips, and it is arranged in a way that enables it to occupy uniformly as much space as possible. Uniform arrangement is essential for achieving uniform heat distribution. It is also essential that cable turns never allowed contacting one another. Contacting turns may result in failure resulting from the consequential melting of the protective insulation due to high heat build-up at the contacting points.  

The controller 

For the controller, we use the SHT21-based humidity and temperature sensor demo board. In the original version of the SHT21-demo board, the sensor is placed on board. In our version, we decided to place the sensor far away from the main board. That was done because we wanted to experiment by placing the sensor in different places inside the incubator in order to find the best spot.

DIY controller for Incubator After performing some experiments, we found that the temperature inside the incubator is slightly different on the corner edges than the stable temperature observed at all other places. Surprisingly, there wasn’t any temperature difference across height inside the incubator. Normally, heat tends to concentrate on top, and we expected to observe higher temperatures near the top than the average observed in other places, but that wasn’t the case. We were happy to observe that phenomenon, because we concluded that the fans used to circulate the air around the incubator, worked perfectly. Forced air circulation kept the temperature constant mostly at all places inside the cabinet. As we mentioned before, there was an exception at near the corner edges of the wooden box. Temperature near the corners was about 0.5 degrees Celsius less than the one observed in all other places. However, that would not cause any problems, as far as the eggs are kept away from the corner edges of the box.

For placing the sensor away from the main board, we have designed a small PCB. The PCB was connected with the main board, threw a four wire cable. Two wires are used for the power supply, and the other two are for the I2C bus. The SHT21 was soldered on the small PCB, and placed inside the incubator at a convenient place, far away from the heating resistor and the corner edges of the box. Our first though was to place the sensor as near as possible to the eggs, but since we observed that the temperature remained stable anywhere inside the cabinet (except from spots near the heating resistor and the corner edges), we decided to place the sensor in a more convenient place, somewhere about the middle of the rear wall, to keep it clean and far away from the young birds.

The SHT21 demo board was placed at the interior of the front panel and we have drilled a rectangular slot for the Display. The display was placed inside the slot, so that it can be viewed from the front. For extra protection, we have covered the display with a small peace of transparent plexiglass.

For automatically turning on and off the heating element, we use a solid state relay. The relay is controlled from the main board, threw a single control line. The line used to control the solid state relay is the DA4 line, from the controller’s IO port. DA3 and DA2 lines are also used for providing warning signals. If the temperature drops below 37 or gets above 38.3 °C, DA2 or DA3 goes high, respectively. Both warning signals remain low when temperature inside the cabinet is at safe levels. These warning lines can be used for triggering buzzers, sending messages or to make a call on your cell phone in case of emergency (if temperature goes outside of the safe region)!

During normal operation, both temperature and relative humidity are displayed simultaneously at the LCD. However, the controller is used only as a thermostat and controls directly only the temperature inside the incubator. Humidity level is controlled indirectly by using two water pans, inside the cabin.

The firmware 

The controller runs a slightly modified version of the original firmware described on the SHT21 humidity and temperature sensor demo board web page. Modifications include controlling of the RA4 I/O pin and implementing a very stable thermostat.

Click on the provided link to download the firmware in .hex file.

Source code files are written in C. Click here if you wish to download the source code (paid download link).

In order to program the PIC18F2620 microcontroller, you will need a PIC programmer. In our project, we have used the MPLAB ICD 3 In-Circuit Debugger - programmer from Microchip.

thermostat is the main component of the system which senses the temperature of the system so that the system's temperature is maintained near a desired setpoint. The thermostat does this by switching the heating element on or off, to maintain the correct temperature. The name is derived from the Greek words thermos "hot" and statos "a standing".

The thermostat switches on and off the heating element at temperatures either side of the setpoint. The extent of the difference is known as hysteresis and prevents too frequent switching (or bouncing) of the controlled equipment. The setpoint in our thermostat is at 37.6°C, and we use a hysteresis of 0.03 degrees centigrade. The thermostat switches on and off the heating element when senses that the temperature is dropping below 37.60°C or rising above 37.63°C , respectively.

The specific setpoint was selected, as being the most appropriate for chicks. However, if you wish to incubate other commonly incubated poultry, you may need to alter the setpoint at a different level. In order to do this, you will only need to set the desired temperature values by modifying the source code. After setting the new values, you must recompile the code and re-program the PIC microcontroller.

At this point, you may be wondered that we possibly could use the three buttons of the humidity and temperature sensor demo board for setting the setpoint without having to recompile the code. Well, you are right! That would be a future update. However, you do not have to wait. You are always welcome to write your own code for adding additional capabilities. 


The egg turner 

Egg turner, and water containers inside the incubatorAn egg turner is great for those who prefer a more hands-off approach to incubation. We bought a turner which includes one set of six universal racks. Each rack is able to hold 7 eggs, so the turner is able to handle up to 42 eggs. An electric motor gently rocks the eggs 4 times a day (24h) backwards and forwards at about 30 degrees in each direction, which prevents the yolk from settling and exercises the embryo. The easily removable rails paired with a dishwasher safe plastic construction allows for easy cleaning.

We used a turner which runs on low voltage. It requires 12V/600mA AC power supply. The AC power is provided from a 12V/3A transformer which is also used to power the thermostat. The egg turner runs independently and can be turned on or off at any time from an external switch. The egg turner's switch was placed on the front panel alongside with to other switches.


The water pans

During normal operation, both temperature and relative humidity are displayed simultaneously at the controller's LCD. However, the controller is used only as a thermostat and controls directly only the temperature inside the incubator. Humidity level is controlled indirectly by using two water pans, inside the cabin.

Due to limited space available, we’ve placed the two water pans on a metal grid, about 20cm above the eggs. We also drilled two holes on the roof and we placed two rubber hoses inside them, in order to be able to supply the pans with fresh water from outside without opening the front door and disturbing the eggs.

The pans were made from two plastic food-containers of about 15x15x4 cm, each. Using one pan filled with fresh water, we had about 60% relative humidity inside the cabinet. Using two pans, we had about 75% RH. After adding two sponges inside the water containers, with the sponges surfaces slightly above the water surface, the humidity level inside the incubator was about 90%.  


Electrical connections

Here, we present the electrical connection diagram of our automatic incubator.

How to use the incubator 

  • Place the eggs carefully into the egg turner. The larger end of each egg should be on the top (the pointy end should be closest to the floor).
  • Turn on the incubator and the egg turner.
  • Fill the water pan (or pans) with warm water. Add a sponge to the water pan if you need to increase the humidity. Relative humidity should be around 65% throughout the incubation, except during the last 3 days when you should raise it to 90%.Replenish the water in the water pan on a regular basis or the humidity levels will drop too low.
  • During the last 3 days remove the eggs from the egg turner. Remove the egg turner from the device and put the eggs on the incubator's floor lying on their sides.
  • After the hatch, remove dry chicks to a prepared area. 

 

About this tutorial

The Automatic Egg Incubator prototype was built and tested in Greece on February of 2013. Many friends have built their own Automatic Egg Incubator, based on the initial prototype. Tests show that the incubator has an average hatch rate of about 84%.

If you have any new ideas, some additions, corrections or complaints feel free to provide feedback. Everyone will appreciate any further contribution.

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