Open-Source Microcontrollers for Science - Open-Source Lab: How to Build Your Own Hardware and Reduce Research Costs - page 64

4.5.1 Specifications
The “Polar Bear” Open-source Environmental Chamber (Bear Chamber) was designed to
provide the necessary environmental control at the lowest possible cost in the shortest amount
of time. The chamber is designed around the shell of a dorm refrigerator and thus has a
work area volume of over 100 l (3.65 cubic feet). It can control the chamber relative humidity
between 10% and 90% and the temperature between the range 25 °C below and 25 °C above
the ambient temperature. The power draw on the Bear Chamber was measured with a Wat
meter during operation and is summarized in Table 4.2 .

Table 4.2
Measured Power Consumption of the Polar Bear Open-Source Environmental Chamber

Setting Power Consumption [W]

Idle 12.5
Heating 48.6
Cooling 115
Dehumidifying 54
Humidifying 67.5
Estimated overall use with chamber closed 57

4.5.2 Bill of materials polar bear open-source environmental
chamber
The list of components, source, number and approximate cost is shown in Table 4.3 . A few
points should be made about the prices listed in Table 4.3 . As with most laboratory equipment
builds, a certain quantity of salvaged components was utilized. For example, in our case, we
had available metal sheets, wires, power supplies and computer fans from our in-lab “store”
of recycled components. Most organizations are constantly discarding old computers. Even
very old computers can gain a new life using a fast and light-weight Linux operating system;
however, even those that are too old to be used as equipment interfaces can be harvested for
their power supplies, heat sinks, wires, fans and case materials. For this project, for example,
salvaged computer components saved about $50 on our total cost, excluding shipping costs.
The prices for purchased components are correct at the time of design for the vendor listed.
When possible, several alternative vendors are also shown. Table 4.3 is also grouped by vendor
in order to try to constrain shipping costs. For those with mature labs, already many of the
components like wiring and simple circuit elements will already be available for trivial or no
costs. As you can see from Table 4.3 , the botom line is the Polar Bear Chamber which can be
built for less than $400 in materials.