Version 11/18/2016

This is a simple and inexpensive incubator for holding samples at or above ambient temperatures. Using the programmable thermostat, temperature can be held constant or programmed to fluctuate diurnally. This incubator is useful for soil samples being baited for Phytophthora species.

The components are available at big box hardware stores and other similar locations:

• a wire shelf kit; ours have 4 shelves, each 13 by 36 inches. Shelves can be placed up to a maximum height of 48 inches. (33 cm x 91 cm x 122 cm)
• construction foam insulation, 1 inch (2.5 cm) thick; one side (placed to the inside) has a reflective Mylar skin
• incandescent rope light as heat source (don't use LEDs as these will not generate enough heat to be of use)
• plug-in programmable thermostat (Lux #WIN100-005 5-2-Day Outlet Programmable Thermostat)
• small circulating fan to help even out temperatures within the chamber - we use a desktop computer cooling fan powered by a 12VDC transformer
• adhesive backed Velcro strips (to hold foam panels together)
• vinyl drip edge flashing (comes in 10 ft lengths, 3 inches wide) - used to make corner edges for foam panels
• aluminum foil tape for sealing edges of insulation and adhering the drip edge flashing
• short extension cords; one for power to the thermostat, another with multiple outlets coming from the thermostat and powering the lights and fan

It will take one person at least several hours to assemble the incubator. The finished chamber is not airtight, as there is some air exchange independent of opening and closing it. We advise use of a min/max thermometer or data logger to makes sure the thermostat set points are giving you the desired temperatures.

External view of an incubator. Note lid and bottom panel. Holes are cut through the bottom panel for the legs of the wire rack. The power cord fits between the back or side panel and bottom panel.

External view of an incubator showing lid. Note how vinyl drip edge is taped to panels. During construction, first tape all edges of foam insulation that will not have the drip edge applied. Edges with drip edge are sealed when this material is applied.

Vinyl drip edge can be attached two different ways. For the first, shown in this detail, the thin rib of plastic that protrudes from the exposed edge has to be planed away near the velcro closures as shown.

Second way to apply the vinyl drip edge. The thin rib on the short edge is pressed into the foam insulation and does not need to be trimmed away. However, the wide exposed edge of drip edge needs to be trimmed to the width of the panel it will adjoin, at least at the top, so the lid will fit tightly. In our chamber, we trimmed the entire edge for the front panel but only the top for the back panel.

Interior view of incubator with lid removed (next to chamber at right) and front panel open. Rope light is strung beneath each shelf and attached with ties. Both fan and rope light turn on when the temperature in the incubator is below the set point of the thermostat. Note velcro strips attached to side of panel. Corresponding strips are attached to the vinyl drip edge of the front panel. Multiple velcro pieces are used along the length of each panel and corresponding vinyl drip edge to hold the incubator together. Don't use more than three or four short pieces of velcro on the front panel that you will be opening up. On the back and side panels, a few short bits of velcro that attach to the bottom panel will improve stability, but don't put these on the front panel. Note how legs go through bottom panel.

Close-up of LUX thermostat. This is programmable and can be used to have temperature ramp up and down diurnally.

Close-up of incubator fan.

 

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