Chickens!

Early in March we decided that hatching some chicks would be a fun project for springtime. We got eggs from Mary at http://www.fosterpoultry.co.uk/ Two Light Sussex hybrid eggs and four Cream Legbars. The Cream Legbars are great since you can sex them shortly after they come out of the egg. Males often have a white spot on the head and girls are more stripy.

Incubator construction

Ingredients:

A foam box (glued together from a larger foam box)
A 25W light bulb and holder (inserted in the right hand side of the box)
A heat mat (left over from reptile cage – I believe it is not really necessary)
Some wire mesh to suspend the eggs (about 1 inch above the heat mat) and to stop the chicks burning themselves on the light.
A bowl for the humidifier/kitchen rag
A IV line for inserting water into the humidifier
A small Halogen bulb (10W)
A 1-wire humidity/temperature sensor.
1x USB controlled relay + PSU to drive the halogen heater

So we construct the box with some contact adhesive and covered any cracks with packing tape. We make two inspection holes in the top and taped them inside and outside to create “double glazing”.

We use a dimmer to set the temperature in the box to ~35°C and rig the computer to control the gap to about 37-38°C by switching on and off the halogen bulb.

Fig. 1: The complete setup.

The humidifier is created from Lego Mindstorms. A single motor runs for 0.1s every 15-120 depending on requirement and pushes the plunger of a 50ml syringe attached to the IV line. NQC source code on github: https://github.com/gbusker/rcx-dose-pump

Fig. 2: The Lego Mindstorms humidifier

The wait

Once the eggs are placed we still spend quite some time controlling temperature and humidity. The temperature is easy – except that after a few days we realise the Raspberry Pi is not stable enough and we switch to the kitchen laptop.

Humidity control is hard at first and only becomes stable once we place a kitchen rag in the humidifier bowl. By dosing water into this we can control humidity to within a few percent. Note that we don’t actively control humidity – we just set the water injection rate by selecting an RCX program that does a small dose every 15,30,60 or 120 seconds.

Below you can see the temperature and humidity profiles. We didn’t so so well with humidity because we controlled it manually in the 10 days and then had some issues with reprogramming the RCX (via crappy IrDA link). The humidity profile in the last week is as it should be – increase humidity before hatching.

month-humi
Fig. 3-4: Temperature and Humidity profiles over the incubation.