The OPEnSampler: A Low-Cost, Low-Weight, Customizable and Modular Open
Source 24-Unit Automatic Water Sampler
Abstract
Reliable automatic water samplers allow repetitive sampling of various
water sources over long periods of time without requiring a researcher
on site, reducing human error as well as the monetary and time costs of
traveling to the field, particularly when the scale of the sample period
is hours or days. The high fixed cost of buying a commercial sampler
with little customizability can be a barrier to research requiring
repetitive samples, such as the analysis of septic water pre- and
post-treatment. DIY automatic samplers proposed in the past sacrifice
maximum volume, customizability, or scope of applications, among other
features, in exchange for a lower net cost. The purpose of this project
was to develop a low-cost, highly customizable, robust water sampler
that is capable of sampling many sources of water for various analytes.
A lightweight aluminum-extrusion frame was designed and assembled,
chosen for its mounting system, strength, and low cost. Water is drawn
from two peristaltic pumps through silicone tubing and directed into 24
foil-lined 250mL bags using solenoid valves. A programmable Arduino Uno
microcontroller connected to a circuit board communicates with a battery
operated real-time clock, initiating sampling stages. Period and volume
settings are programmable in-field by the user via serial commands. The
OPEnSampler is an open design, allowing the user to decide what
components to use and the modular theme of the frame allows fast
mounting of new manufactured or 3D printed components. The 24-bag system
weighs less than 10kg and the material cost is under $450. Up to 6L of
sample water can be drawn at a rate of 100mL/minute in either direction.
Faster flowrates are achieved by using more powerful peristaltic pumps.
Future design changes could allow a greater maximum volume by filling
the unused space with more containers and adding GSM communications to
send real time status information.