Safe, repeatable, scaleble and DIY

This DIY incubator project is made to create an incubation/drying solution that is safe, repeatable and scalable. Our need for this arose when looking around at DIY incubators and realising that many of them where either a fire hazard, not scalable because they used old fridges or both.

Our incubator aims to use standardised components and requires virtually no electronical knowledge to build a safe machine.

Supplies

You don't need a lot of specialised tools. A drill and a file will bring you almost all the way. The only 'special' tool that we used was a 100mm holesaw which is an unusually large size.

Step 1: Choosing a Cart

To make this project scalable and repeatable we choose to use to use insulated kitchen/hotel carts in the Gastronorm standard. This is a European kitchenware standard which means you can buy tray's for these carts anywhere. These carts are normally used to keep food warm or cold for a long period of time.

We bought a second hand Cambro UPC1600 cart with the GN2/1 ratio that has two compartments. This way we can run two different processes at the same time.

Step 2: Heating Unit

The core of the heating unit is a resistor heating element. These can be bought in all shapes, sizes and capacities. The element is sandwiched between two stainless dishes of Gastronorm GN1/1 with the bottom one perforated. These perforations allow for easy installation of the heating element with PCB standoffs and washers.

The element is wired with it's two ends to the power cable. The ground wire of the cable is connected to the bottom scale. In our heating unit we decided to make the electronic connections with wire splice connectors to allow for easy maintenance and reparations. The cable exits the enclosure through a cable gland with locknut.

The bolts that keep the gastronorm dishes together are stainless and fastened with locking nuts.

Step 3: Ventilation

To control the temperature not only by heating but also by cooling a wall ventilator is added in the bottom of the compartment wall. We went for a 100mm fan to push a lot of air through the compartment when it's cooling down. This big volume of air cools down the compartment faster than a small one while also pushing out more humid air.

With our ventilator we had to wire up the cable ourselves. Make sure you plan where your temperature controller is going to be and afterward buy a cable that matches the distance from your controller to your ventilation hole.

Step 4: Control Unit

We choose to control the temperature with an Ink Bird controller. This is a plug and play solution for temperature control that is mainly used by hobby beer brewers. They can be bought in a lot of variations that enable different temperature steps and wifi control.

With this controller you can set a temperature and some heating and cooling parameters and the rest is automatic. When the temperature drops below your set point the Ink Bird will switch on the plug marked "Heating". In this you plug your heating element.

When the temperature rises above your setpoint the Inkbird switches on the "Cooling" plug in which we put our ventilator.

You could also build your own controller with something like a STC-1000 module. This however requires a lot more knowledge of electrical circuits and installation. If you don't have this knowledge it's best to not build your own circuits that control 230 volts.

Step 5: Intallation

This step is most specific for our second hand food cart. Your proces may vary depending on the cart and the materials that it's constructed with.

Our proces was as follows:

Cut 100mm holes in the bottom of the back walls of both compartments for the fan.
File a slot for the heating elements powercable.
Drill a 6mm hole in the top of the back wall for the Ink Bird temperature sensor.
Mount the temperature sensor to the roof of the compartments.
- For this we used a simple 3D printed bracket (found here). But any way of fastening that doesn't cover up the metal part of the sensor is fine.
Fasten the cables to the cart.
Mount the Ink Bird controller to an easy to reach place on the outside of your cart.

In our case we build a display stand on top of the cart with the two controllers next to each other.