I'm building a chicken egg incubator! Long story short I moved from NYC to Idaho for a gal. Her father is a farmer, and is in need of a large chicken incubator. The size of incubator he's interested in sell usually for $900 to $2,000 new and are way out of his budget. Seeing as I love electronics, I offered to help build one. Because minds work better in groups, I'm looking for some feedback on my ideas/design.Overview
For those of you who are not familiar with the requirements of incubating a chicken egg, here are the basics:
- Keep temperature between 99.5 to 100.0f (99.9f is best).
- Temperature fluctuation of +/- 0.5f is tolerable over short periods of time, however fluctuation of +/- 1.0f over long periods of time can be fatal.
- Humidity should be kept at 58 - 60%. During the last two to three days, while hatching, humidity should be increased to 65%+.
- Eggs must be "turned" roughly +/- 30 degrees five times a day, except for the last two to three days during hatching.
(The exact temperature/humidity required is also dependent on the breed, however the above is generally true for all chicken eggs.)
The incubator needs to be designed to hold ~200 to 300 eggs, and because of this it will be a multi-level incubator, much like this one:
Each shelf will hold ~90 - 108 (maybe less or more, not sure yet) eggs. The multi-level design is required to be a forced-air incubator, to make sure air is moving around and the temperature is relatively even on all levels so fans will be incorporated into the design.
That's a general overview of the project. Onto the specific:Temperature
From my research, many one-level incubators simply use one or two 60 - 75w light bulbs, that are connected to a commercial temperature-controlled relay. This type of heating system will not work very efficiently for a multi-level incubator as the area is larger. The light bulbs also take a period of time to heat up/cool down, which will affect the ability to adjust temperature. Because of this, I'm considering using a couple 40 - 100w heating element/coil. There will be one near the top and bottom, or one near each level. In addition, there will also be a fan blowing air past the heating element to distribute the heat.Humidity
Most large commercial incubators I've seen have a water tray on the top/bottom of the incubator. Humidity is dependent on the surface area of the exposed water from my understanding. I'm currently considering having a water container (like a hamster's water bottle) hanging outside of the incubator with an electronically-controlled valve on the inside that feeds water into a tray to increase humidity. Decreasing humidity can be accomplished (I hope) but simply increasing the fan's speed and moving the humid air out.Electronics
The entire system will be controlled by a LeafLabs Maple Mini
because I love LeafLabs and the STM32 (plus it's size and cost works in the project's favor)... and I happen to have a few.
For temperature/humidity monitoring, I will be using the DHT22
temperature/humidity sensor, as for the cost it provides both sensors with relatively good accuracy. I plan to have 3 or 4 scattered around the incubator, probably one on each level.
I'll be including a DS1307 RTC
, to keep track of what day in the cycle (to stop turning and increase humidity 2-3 days prior to the end of the 21-day cycle). Because I'm primarily care about the day, I'm not to concerned about the accuracy. I may even go with a software+EEPROM-based RTC to save some money.
And of course an LCD
to view data on. I may or may not include an SD/SPI-Flash logging capability. That's dependent on how things go.
As far as temperature/humidity control goes, I'll be implementing a PID controller. Each heating element will be turned on/off dependent on the temperature sensors. If it becomes too hot, the fans will help remove the warmer air. Humidity control will probably not run on a PID controller, or may with a larger window as I don't want to A) charge humidity rapidly and B) use up all the water in the container.Questions For You
Any suggestions regarding the temperature/humidity control? Thoughts on using heat elements vs light bulbs? Anyone know a good source for heating elements by the way (mcmaster's are too expensive and not the right kind)? Are the ones out of old coffee machines or water heaters too powerful (they're like 500 - 1500w)? I'm assuming weaker 40w units can simply be controlled with an SSR and a 12v supply or something along that line, correct? Or are they all 125 VAC? Anyone have a datasheet on one?
Any help would be appreciated, thanks!