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Our home built incubators
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240v - a word of
warning
You are welcome to copy our plans, but please note that some of the
wiring necessary to complete this project is 240v wiring. All 240v
wiring must be done by a licensed electrician. We are not responsible
for any injuries/accidents caused as a consequence of copying our
plans. What worked for us may not work for you. |
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Our first incubators
These were a 12 egg unit and a 24 egg unit made by IM. They are
available through a number of outlets in Australia. They are compact and fit nicely on top of our kitchen
counter; they have a clear perspex front panel through which we can
observe the newly hatched chicks, and they have controls that are simple
and work well.
This IM 24 is an automatic unit. It turns the eggs regularly by 90
degrees.
It took us some time to get the humidity level inside the incubators
right. We ended up using an unglazed terracotta dish of a larger size
than the plastic dish supplied with the unit. We hatched a lot of eggs
last season from our two IM incubators and had on average a success
rate of 40% for eggs airmailed to Tasmania. When we use our own eggs
the success rate is up to 90%. |
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Different types of
incubators: advantages and disadvantages to consider
| Manual, semi-automatic, or automatic |
simple models will be manual ones where the unit must be opened a
few times per day to turn the eggs by hand. Hens will
turn the eggs in their nest many times a day; turning is necessary so
that the developing embryo can use all the nutrients provided in
the egg. Half-automatic models allow you to turn all eggs at once with
a handle without opening the incubator; fully automatic units use
motors to turn the trays. Our small 12 egg incubator and 24 egg
incubator are automatic incubators, but we use the small one as a
manual incubator, because that allows us to put 20 eggs in the unit!
Hand turning is no big deal and takes only a minute. |
| Fan forced or still air |
it is very important to have a fan-forced incubator. A fan inside
the incubator evenly distributes the heat throughout the incubator.
Colder spots are much less of a problem here than in still-air units.
Many cheap still-air incubators can be retro-fitted with a fan. |
| The thermostat and the temperature |
some incubators use relatively simple and cheap thermostats like
a wafer control; others are fitted with sophisticated
electronic thermostats. As long as the incubation temperature is held
constant at 37.6 degrees Celsius it does not matter how this is done.
The average temperature is very important as the eggs need a
while to change their core temperature; it does not matter too much
if there is some fluctuation around the 37.6 degrees in the incubator
– as long as the average is right. If the eggs were incubated at a
slightly lower temperature the chicks will hatch later than at day 21,
if the temperature was higher they will hatch earlier. It is important
to check the incubation temperature with a good thermometer, but the
time it takes for the chicks to hatch is also a good indication if our incubation
temperature was right. |
| Humidity control and fresh
air |
the humidity inside the incubator must be
right too. We can change the humidity in our incubators by
putting saucers with water inside them. The larger the surface area of
the water the higher the humidity will get. Chicks need oxygen to
develop and incubators have an air-inlet and an air-outlet. The more
outside air is sucked into the incubator the lower the humidity will
be. We leave the vents fully open for the first 19 days and regulate
the humidity by changing the size of the water-filled saucer in the
incubator. It’s not as difficult as it sounds. Once we had found the
right sized saucer we never had to change this again. Expensive
humidity control systems are available for purchase, but we never felt
the need. Humidity is easily measured with a wet bulb thermometer. A
wet bulb thermometer gives a “wet reading”. The correct wet
reading during incubation is 28 to 31 degrees Celsius up to day 18. It
has to be raised for the last three days to 32 to 34 degrees. |
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Our design
We spent a lot of time on the internet looking at
incubators that other people built. The backyard
poultry website is a very good source of information. Many
projects are described on this site. This
link is particularly valuable. It is a thread dedicated to
home-built incubators. |
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The incubator we would like to build:
After looking at a lot of home-built incubators on the
internet
we came up with this list of design parameters:
- our incubator has to present value for money
- it should be easy to build
- it has to have room for around 90 eggs
- it must give good hatching results and be reliable
- it can be manual (we don't mind turning the eggs by hand)
- a PID controller is preferable because of its reliability
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height of sides is 250mm
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This is our design:
- a simple rectangular box with two additional dividing walls and a
hinged lid. The centre compartment provides room for the eggs. The two small
compartments at each end are the heating chambers.
- the centre compartment measures 550mm x 550mm and has enough room for 80
to 100 eggs depending on their size
- the egg tray is home-made from heavy bird mesh that we folded so that the
eggs rest securely on the tray in rows of eight to twelve
- the heating compartments are 150mm wide with enough room for the heating
elements. We chose one heating compartment at each end for improved
distribution of heat throughout the egg compartment and for added security
in case of component failure |
Material for the box:
18mm structural CD plywood painted well on the inside. All joints
sealed with acrylic gap sealer to protect against damage by moisture.
The following pieces are needed:
2 x short sides @
550mm x 250mm |
2 x long sides @
814mm x 250mm |
2 x dividers @
514mm x 232mm |
1 x base-plate @
814mm x 514mm |
2 x supports for egg tray @ 532mm |
Material for the lid:
This could be 18mm plywood but I built my lids lighter and used
7mm structural bracing ply, one piece at 550mm x 850mm. I strengthened
the edges with 45mm x 35mm pine. Just remember to add a piece of pine
above each divider to seal the heating compartments from the egg
chamber. You do not need to add a window. I prefer to have a window
though. I used old pieces of 3mm standard window glass above the egg
chamber. In one of my incubators I used two layers of glass with an air gap
between them for insulation. This is optional. If you are concerned
about heat loss through the window you could just as easily cover the
window (e.g. with a towel) when you are not looking. Add a couple of
standard door hinges and the lid is finished.
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Heat distribution inside the
box:
inexpensive 12v computer fans are set into the top corner of both
dividers diagonally opposite each other. The two fans are connected to
a 12v plug pack available from outlets such as Jaycar or Dick Smith.
Both fans run constantly. The fans suck air into the heating
compartments and hot air is pushed out of the heating
compartment through the ventilation holes. The egg tray sits at
a height above the ventilation holes, but below the fan. The hot air is
pushed into the egg chamber and rises between the eggs before it is
pulled back into the heating compartments by the fans. You can
experiment with different hole sizes and numbers to achieve the best
distribution of heat, but the five 35mm holes work well in our
incubator. |
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The heat sources:
Most incubators use resistance wire or incandescent light globes as a
heat source. Resistance wire is not as
easily obtained as light globes and can be quite expensive. We
wanted to keep things simple and use light as a heat source. A PID
controller switches the lights on and off quite frequently and we were worried
about frequent burn-outs of incandescent globes. Our prototype used
halogen globes. The transformers soft-start the halogen globes and we
expected the 12v halogen globes to last very well. This photo
shows the 50w halogen globe assemblies in each heat compartment. This
was not successful! The halogen globes simply didn't produce enough
heat.
The second photo shows another incubator we built. The mesh tray is
flat so that it can be used as a hatcher. Here we installed four
incandescent light globes with 60w each. These four globes bring up the
unit to the right temperature in just a few minutes. Over a period of two
month of constant use only two light globes blew in two incubators.
This proves that PID controllers are indeed suitable to control light
globes in incubators. Four globes per incubator are an excellent
safety feature. The incubator should still be able to keep its
temperature even if two of the four globes burn out. Incandescent
globes are being phased out in Australia, but the candle type 60w
globes remain available. This photo also shows how the 12v fans are
placed diagonally across from each other.
Note: we attached bird mesh to the front of the fans so that
the chicks
can't stick their heads into the fans!
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Temperature control
Temperature control is crucial for achieving good hatching results. People
in China incubated eggs in warm ashes and tested the temperature by pressing
the eggs against their eye sockets: if the egg felt neither hot nor cold
but just pleasantly warm, then the temperature was right. Kerosene incubators
were used on many farms up to the middle of last century. To achieve the
correct temperature was very much a matter of skill with those incubators,
but it is possible to incubate eggs with very simple means. Today however
industrial process controllers are available. They have dropped in price to
such an extent that they are now just as affordable as simple wafer
controllers. A wafer controller has moving parts and they can wear. A PID
controller is a computer controller without moving parts. If it is connected
to a solid state relay, then no moving parts at all are required to switch
the heating elements. But there are other advantages. A wafer controller can
only switch the heat once a certain temperature is reached. A PID controller
can turn the heat off BEFORE the desired temperature is reached so that the
heat of the still warm elements is sufficient to just reach the required
temperature. But this is a gross simplification of what a PID controller is.
It gets a bit technical here and I would just like to quote Wikipedia:
| A proportional–integral–derivative controller
(PID controller) is a generic control
loop feedback
mechanism (controller)
widely used in industrial control
systems. A PID controller attempts to correct the error between a
measured process
variable and a desired setpoint
by calculating and then outputting a corrective action that can adjust
the process accordingly and rapidly, to keep the error minimal. |
Let's just say that PID controllers are the ideal tool
to control the temperature in any type of incubator. Once they are set we
can forget them. The temperature will always be right, unless something
brakes down. We could even connect an alarm to our PID controller to alert
us should
that happen. But which PID controller to choose?
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Auber Instruments is a company
located in Georgia, USA. Their controllers have a very good
reputation. We dealt with them twice and purchased parts from their website.
Both times we received them within ten working days.
These are the items we use in our incubators:
- the
universal 1/16 DIN PID temperature controller
- a
miniature RTD sensor. This is the temperature probe that is placed
inside the incubator
- a
25A solid state relay. This is the relay that is controlled by the
PID and actually switches the heating elements on/off
The total cost of all parts at time of writing (September 09) is US
$79 plus around US$15 airfreight. For a total of around A$120 this
buys us computer controlled switchgear without moving parts that is of
better quality than most of the parts used in commercially available
incubators that sell for up to two thousand dollars!
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How we set up the incubator with the PID
controller
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The controller is connected to 240v. The temperature probe is
placed inside the egg compartment at the height of the eggs. If your
probe is permanently mounted (ours is not) it is very important to
check the position of the probe every time you open and close the
incubator. The relay connects to the PID and switches the globes. The PID comes with a set of instructions and all pins on the PID
are clearly marked. There isn't much that can go wrong here.
Programming the PID can be as complicated or as simple as you want
to make it. We opted for simple! Once the SSR (solid state relay) and the probe are
connected, the PID needs to be set for the correct type of
probe installed. The manual explains how this is done. The PID
parameters that can be changed by the user are the proportional
constant, the integral time and the derivative time.
But we didn't set any of these parameters! We just pressed the PID's
auto-tune button and let it find the best values itself!
One important parameter that can be changed is the cycle rate.
The cycle rate determines how often the heating elements are
switched on and off. It is factory-set to two seconds. This would
result in the PID switching the light globes on/off as often as
every two seconds. We changed this setting to thirty seconds to
extend the life of the globes. Thirty seconds as cycle-rate seems to
be a good compromise between accuracy of the system and life
expectancy of the globes.
That's it! Once set up like this the PID will run the incubator
by itself!
Note: do not assume that the probe and the PID are
temperature calibrated. We checked the measured temperature as
displayed by the PID (the red numbers) with a digital spot-check thermometer. The PID constantly registers two degrees F too high,
meaning we need to set it (the green numbers) two degrees F higher
than the temperature required. Once you incubate eggs you will find
out if your temperature was correct after 21 days! If the chicks
hatch on day 21 your temperature was spot on. If they hatch before
that day, then it was too high; if they hatch later, then it was too
low. Make your adjustment for the next batch of eggs! Another
note: we prefer to set the controller to Fahrenheit rather than
Celsius as it is not possible to use decimals on this unit. |
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Humidity and oxygen control
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Both of our home-built incubators in operation
the water-filled terracotta saucers and the air intake pipes are
visible in both incubators
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Oxygen: eggs need oxygen to develop. The embryos use a lot of oxygen and would die
in their shell if no oxygen was supplied to the incubator. We use the fans
to suck fresh air into the incubators. We assumed that air intakes of about
30mm each in diameter on the front and the back would be sufficient for the
size of our incubators. Plastic tubing channels fresh air from the outside
through these openings to a spot directly in front of the fans. Five 12mm
outlet holes each close to the floor of the incubator in the front and the
back let used air escape.
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Intakes and outlets in front and back of incubators
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Humidity: we use terracotta dishes filled with water to control the
humidity in the incubators. A wet bulb thermometer measures the humidity; we
tried different sizes of dishes until we found a combination of two or
three dishes that create the correct humidity. Provided we keep them filled
the humidity will be right.
Note: to experiment with the airflow we used sticky
tape to partially cover inlet and outlet openings. Now we leave all openings
uncovered. It works well this way. Heat loss through these openings is
acceptable.
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Incubators or hatchers?
The first 20 to 21 days of egg development
(chooks) are a relatively clean process. The eggs sit in the incubator and
all the action takes place inside the eggs (hopefully!). The messy part of
the process begins when the chicks crack the eggshell and pip! It is amazing
how dirty an incubator can get when a dozen or more chicks have shed their
shells, smeared the remainders of the egg yolk all over the place and lost
uncountable tiny baby feathers. It is a dirty environment and infections can
develop and destroy everything inside the incubator. It is advantageous to
use an incubator until day 18 and then to transfer the eggs into a separate
hatcher. The hatcher is nothing else but another incubator with a flat floor
that makes it possible for the chicks to get a good footing once they have
hatched. The actual incubator stays clean this way. The room freed by the
transfer of eggs into the hatcher can be used for the next lot of eggs. That
is the theory! In our case theory and practice differ. Once we had built our
dedicated hatcher we filled it not only with hatching eggs but also with
those eggs that didn't fit into the other incubator. We should really build a
third one, so that that one could be the designated hatcher! No, we have to
draw the line somewhere!
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Our hatcher: we built a dedicated hatcher to keep the
messy hatching chicks out of the original incubator and away
from eggs that are not ready to hatch. But then we built hatching
cages and that freed up room... |
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The last three days in the incubator/hatcher
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This is the time when the chicks are starting to
pip. Often they can be heard chirping a day before they break through the
shell. It can take them over a day to free themselves from the shell. The
eggs are no longer turned after day 18. Automatic incubators have special
hatching trays where the chicks can hatch safely . In manual incubators the
eggs can stay where they are. It is very important to keep the moisture up
during these last days. Once the chick has broken through the egg a small
part of the egg’s membrane is exposed and could dry out if the humidity is
too low. If the membrane is too dry the chick will stick to it and will not
be able to break out of the egg. We try to open the incubator as little as possible
during this time. Sometimes we use a small water sprayer to moisten the eggs while
being careful not to have water run into the pipped eggs (the chicks could
drown!). Once the first chick is out things get very hectic in the
incubator! After a short while it will get up and start to kick the other
eggs around. This is quite normal and actually seems to encourage the other
chicks to work a bit harder at getting rid of their shells. Chicks do not
need water or feed for a day or two. They are well nourished from the yolk. We
leave them in the incubator until their feathers have dried. This may take
up to a day. Then they are transferred into a brooder where a heat-lamp
keeps them warm for the next three to four weeks.
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The total cost
| plywood |
$60 |
| paint & sealer |
$20 |
| hinges |
$5 |
| bird mesh |
$7 |
| 12v fans |
$20 |
| 12v plug pack |
$25 |
| batten holders for globes |
$20 |
| light globes |
$10 |
| PID controller, probe, SSR |
$120 |
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total cost less
than $300 |
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