Incubator components

[Penturner]

Hello folks, I am in the process of building a home made incubator. So far I have found two, yes two, small ice makers that broke down and made a really nice chest shaped box with a back panel for mounting things like indicators or monitors if I want them without putting hold into the egg chamber.
I am really really against breaking the integrity of the egg chamber in any way.
I have also gotten 4 alcohol thermometers that all agree in their readings so chances are pretty high they are accurate. I also got one digital thermometer / Humidity meter that is dead on in agreement with the other 4 thermometers but low by 10% on humidity determined by the salt solution method of testing it. I also have two 12 volt computer fans but no way to power them at this time
So far I have not selected a thermostat, heat source, water container, or settled on a forced air system.
I am looking for specific suggestions on the above 4 items based upon accuracy and reliability. I have read all the home made bator articles and researched this group on information about bator for the last 2 weeks. i realize that hot water heaters thermostats are commonly used. I am of the opinion that this is the common practice more due to the convenience and expense that for accuracy. I am not interested in convenience or expense so this is a chance to list the components of your dreams sort of thing. I am trying to build a bator that I can experiment with. I will do everything from monitor mock eggs to actually hatching chicks with it.
I am more interested in a heat source that actually heats the entire bator over one that is simply cheap and easy. I am looking at actually having a humidifier that can be turned on and off to control humidity rather than a passive system. I am also interested in a accurate thermostat over a low priced one.
Please help with suggestions since information here is pretty lean on the quality side although abundant on the low cost side of the issue.
Thanks

 

[Davaroo]

Quote:
Go to the thrift stores in your area and scrounge up 12vdc "wall wart" power supplies. Problem solved.

So far I have not selected a thermostat,
I realize that hot water heater thermostats are commonly used. I am of the opinion that this is the common practice more due to the convenience and expense than for accuracy. I am not interested in convenience or expense, so this is a chance to list the components of your dreams sort of thing.

Cost is no object, in the pursuit of perfection? Good man!

You are right, water heater thermostats are hardly accurate enough, usually varying by as much as 20 degrees around their set points. They are designed to control a buffered water tank, not an air mass. This leads to wide fluctuations and potential hysteresis control problems. This is a shared problem among nearly all low cost controllers, although the gas filled wafer discs offer the least problem along these lines. I suggest those that are successful with water heater thermo's are so because they control a relatively large air mass in a well insulated chamber.

Ideally, you want a programmable thermostat with a thermocouple sensor. These are common in industrial applications and can be found on ebay, often used. I have two or three, myself. I would do my best to obtain some of these.

NOTE: We are controlling egg temperature via convection, using heated air. The egg is not heated directly.
This means it is a good idea to use thermal buffering with your monitoring thermometers, and possibly your thermocouples, too. This allows us to monitor and control the actual egg temperature as opposed to the air temperature. This produces more stable egg temperatures. Here's the concept, explained:

http://shilala.homestead.com/weasel.html

Heat source
I am more interested in a heat source that actually heats the entire 'bator over one that is simply cheap and easy.

All incubators, cheap or costly, heat the air mass. The challenges of directly heating the egg are insurmountable with the current state of equipment. Luckily, the source of heat is not critical. However, for most applications, low-wattage electric coil heaters are best. Incandescent light bulbs are probably the next best choice and I use a combination of the two. *
You can get these coil heaters for incubators as replacement parts, or go with more elaborate ones if you wish. After much experimenting myself, I recommend those designed for incubators. They are low cost, they heat slowly (which prevents temp spiking), they have long life and are reliable.

Humidity
I am looking at actually having a humidifier that can be turned on and off to control humidity rather than a passive system.

Humidity control via mist dispersion is doable, but isn't as needed as you may think. It's a paradox of humidity in incubation that it is important - but it doesn't require elaborate controls.
Since oxygen/carbon dioxide respiration must occur in the incubator, the chamber is essentially open to the atmosphere via the vents. Air in, CO2 out. Unless you rigidly control these two gaseous exchanges (exceedingly difficult), you'll need open venting. This means the chamber is subject to ambient vapor (barometric) pressure. This single factor has as much to do with ambient humidity within the chamber as anything - and is the most often overlooked element.
Simple is better with humidity control. An open pan with regulated surface area, has proven to be adequate, in my experience. I would urge you to read the sticky on Dry Incubation found in the link shown below for greater insight on the role of humidity:
https://www.backyardchickens.com/LC-DryIncubation.html

Forced air system.

For better control, controlled air mass exchange will always give you greater control over that which uses convection alone. In short, use fans. In addition, the greater the air mass the more control stability it will exhibit. One of the problems with temperature spiking and general temperature control in small incubators is because a small air mass has no inertia. Heater comes on , everything gets hot, fast. This causes the thermostat to shut down and everything cools off - fast. The cycle reverses and you get the rapid and sometime wide swings so common in small incubators.
(This is also why I advocate thermal buffering. Several soft drink bottles inside the chamber, filled with water, will stabilize this behavior to a great degree.)

Best practice is to precondition the air (heating/humdity) within a smaller chamber (roughly 1/5-1/3 the volume of the total mass), then expel the conditioned air into the incubation chamber. Circulation is achieved via directional flow and baffling.

Your every effort should be geared towards precise control and stability. Take a look at the Sportsman type incubators, or laboratory type incubators and make every effort to reproduce them.

* It might interest you to know that incandescent bulbs are soon to go the way of the dodo. Federal legislation has been enacted that starts us on the road to seeing them banned within a decade or sooner. Fluorescent bulbs are replacing them, making coil heaters all the more attractive going forward.​