Incubator

Wyandotte chick

Wyandotte chick

In 2015 we began hatching Wyandotte eggs using a small bar fridge that had previously been converted to a reptile egg incubator. After a moderately successful season, it was decided that we needed a better solution in order to continue with the work as well as hopefully improve our hatch rate. My wife wanted something bigger, with improved airflow and more control over humidity. She also wanted a better egg turning system. The result was a built-in unit that I will detail here.

Housing

Egg Incubator Cabinet

The overall layout. The roughed in brooder can be seen above the incubator and control cavities.

At its heart, the new incubator is an aquarium turned on its side and surrounded by Roxul insulation. This provides both an easy to clean interior surface as well as good thermal performance. The door is a removable board with attached 2″ (R-10) rigid foam insulation. It was originally cut to fit as a shutter in our West window, but we opted to replace it with a thermal blind and so, with a few cuts, it made for a good friction fit. The entrance into the incubator has been left fairly large in order to allow for good access as well as for the removal of the egg turning rack for lock-down as well as for cleaning between runs.

Incubator insulation

Aquarium surrounded by insulation, egg turner in place and entrance framing roughed in.

Above the sideways aquarium is a cavity meant to house the heating bulbs, a fan, additional wires, trays of water for humidification, or anything else that is required. A conduit containing nine lengths of 16 gauge wire as well as a cluster of data wiring cut from an old parallel cable was run from this cavity through to a cabinet outside of the insulated area. A separate 16/2 extension cord was run through for the egg turner. Not all of the electrical wires are needed at this time and I have no use for the data cable, but I had them on hand and I learned long ago that it is always useful to run more cord than you need in order to accommodate future upgrades.

The outside cabinet is also furnished with a 4-outlet electrical box powered with a 14/2 mains line from the same circuit as the aquarium, brooder and gun cabinet lighting. At the moment, the box contains two duplex outlets — one for the egg turner timer and the other for the fan and heating circuits.

Incubator facade

The completed unit with the doors in place and a layer of paint. The thermostat was mounted so that its display could be seen from the outside.

Heating and Ventilation

Incubator Wiring Diagram

Wiring diagram for the incubator heating, fan and egg turner functions.

Heating control is provided by an STC-1000 thermostat module that we had purchased for the bar fridge incubator when we changed it over from a reptile egg incubator to a chicken egg incubator. The thermostat remains the only component of the system bought specifically for this project, with the rest having been pulled from the parts shed (which will be documented in a future blog entry) and representing materials acquired from dumpsters, yard sales or other opportunities over the years. The thermostat is plugged into the mains power, with a jumper from hot wire of the mains to one side of the heating relay. The relay controls two bulbs inside the cavity above the aquarium. These lights are wired in parallel so that if one burns out the other continues to heat the incubator. Two additional wires are used to connect the STC-1000 to a thermistor for temperature sensing. The thermistor is on a long lead so that its position can be modified based on our experiences with temperature distribution throughout the unit.

Fan duct in place

The fan duct installed and with the server fan mounted above.

Also included in the top cavity is a computer server fan that runs on mains AC current. This produces a good deal of air circulation silently and without excess heat build-up. The fan is mounted to some ducting bent from a piece of salvaged aluminum siding and taped in place using house sheathing tape. This directs the air from the upper cavity to a wide slit at the top of the aquarium, pointed in the opposite direction from the heating bulbs. Air can then return to the upper cavity from the opposite end of the aquarium. The ducting is constructed with an additional panel and bracket to the side, which can be used to suspend a humidity gauge/thermometer and the thermistor for the STC-1000 in the upper portion of the aquarium.

Vent and baffle

An vent with adjustable baffle allows fresh air into the incubator.

Although it would be nice to be able to endlessly recirculate air of the appropriate temperature and humidity, some fresh air is required for the health of the eggs. A piece of plastic plumbing inserted through the wall of the incubator cabinet is used to pull fresh air into the enclosure. A simple baffle constructed from a bit of plastic, a little house sheathing tape and some solid copper 14 gauge wire was zip-tied to the tube. It can be rotated to create a larger or smaller opening. The air enters near the bulbs so that it will be pre-warmed a bit if the incubator is in a heating cycle before being sent into the lower chamber by the fan.

After all the mechanical elements have been installed, the upper chamber still has sufficient space to house a shallow tray of water if this proves necessary for maintaining adequate humidity.

Egg Turner

After some consideration, it was decided to install an egg turner rather than an egg tilter. Although less space efficient than an egg tilter, I felt this might lend itself to a more effective DIY solution than the egg tilter that I had built for the bar fridge incubator. The business end of the turner is a piece of plastic-coated wire shelving that I cut to length. I removed every alternate rung in order to create spacing suitable for eggs. I then fashioned a bit of an arch-shaped bracket from a piece of scrap aluminum onto which I could mount the motor.

The egg turner

The egg turning rack installed with a dozen eggs in place for a function test.

In order to ensure the rack moves in a straight line, I mounted the front onto a salvaged drawer slide. The back of the rack has a single small wheel mounted to the mid-point. This allows the whole unit to reciprocate smoothly along a path approximately 10″ long, which is greater than the circumference of our eggs and thus should ensure complete rotation from one extreme to the other.

Egg turner motor and gearing

The egg turner motor group. A 120V/3RPM gear motor turns a second gear, affixed to an arm.

The motor for the unit is a 120V 3RPM gear motor I had used in the original bar fridge incubator. I mounted it to a bracket alongside a larger gear, bringing the speed of the unit down to about 1.3RPM. The gear turns an arm, to which I affixed a machine bolt at approximately 5″ from the center, for a total throw of about 10″. I then cut the head off of the bolt and ground the cut end smooth. The unthreaded portion of the bolt fits inside of the mounting point to a linear bearing and rod that was salvaged from an old broken hand mitre saw. The rod is mounted perpendicular to the direction of the rack’s travel and allows the motor’s motion to be converted to reciprocating motion in one direction without adding any lateral pressure.

The entire system was designed to be a bit flexible in order to remove the need for precise machining. As a result, the peg can be removed from the linear bearing simply by pushing it downwards and the entire rack tilted out of the drawer slide and removed in a matter of seconds. Installation is just as quick.

The motor is plugged into a 16/2 extension cord which is run into the cabinet. Here it is plugged into a digital timer that allows for the turner to operate for periods as short as a minute, as many times a day as is required. The digital timer used is a style that appears to be popular in my area and can usually be picked up for a dollar or so at charity shops. Although the timers use two button cells to maintain their programming if the mains power goes out, I prefer to re-wire them to use two AA batteries in an external battery holder. In one case I also had to replace the main relay in one of them with a compatible component I had on hand. For a couple bucks and a bit of soldering, though, I have found them to be useful devices and currently run several. They are much more reliable and quieter than mechanical timers and are much more precise, allowing intervals of 1 minute rather than the standard 15-minute increments on their mechanical counterparts.

Brooder

Brooder

Week-old chicks in their brooder.

Heating element for the chick brooder.

Heating element for the chick brooder.

I built a brooder for the newly hatched chicks directly above the incubator. For the first year, we had used a converted snake enclosure that we suitably furnished and experienced no issues. The new unit has a built-in light fixture which is connected to the same cord as the lighting for the aquarium above. By plugging it into one of the available outlets in the lower cabinet or into its timer in the lower cabinet, the light can function 24/7 for the first few days after hatching (with the aquarium light being turned on and off manually) or can be turned off automatically at night.

For additional heat, I constructed an adjustable scissor-frame that holds up two pieces of tile sandwiching a piece of 12″ heat tape. Previously used to provide belly heat for reptiles, the heat tape now warms the slate and allows the chicks to either sit on top or snuggle in underneath. The latter option provides a situation analogous to the heat they would derive from tucking in underneath a mother hen. As the chicks grow, the platform can be raised to provide more room underneath and a higher perch on top.

Our dog meeting some newly hatched chicks.

Our dog meeting some newly hatched chicks in the old brooder — a converted snake enclosure.

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