LIGHTWEIGHT, LOW-COST PERISTALTIC PUMP FOR STREAM TRACER INJECTIONS

Constant rate tracer injections typically rely on a peristaltic pump, but few pumps are adapted to extreme field conditions. Pumps used by researchers generally fall into two categories: (1) lab-based designs implemented in a field setting or (2) do-it-yourself pump designs constructed by the researcher. Lab-based designs are often expensive (>$1,000) and sensitive to damage and moisture common in a field setting, and both pump categories often require large and heavy batteries to drive long injections at high flow rates (>1 L/min). The purpose of this study was to develop a cost-effective, do-it-yourself alternative ideal for robust field conditions. We used a bipolar stepper motor (12V-36V, 1.5A) connected to a microstep driver (40V, 4A) to create a continuous peristaltic rotation. The pump is controlled by an Arduino Uno microchip processing board, allowing for variable pump rates to be defined by the user. Waterproof housing was constructed using a Pelican 1200 case (7.29" x 4.78" x 3.33"), which can support up to 2 motor systems per case, allowing for dual tracers or double flow rate. Each motor system only draws ~2A of current, allowing for extended battery life using only a small sealed lead acid 12V battery. Batteries can also be stored in an adjacent Pelican 1200 case for a complete weather-proof system. Our maximum flow rate was ~1 L/min per pump, or 2 L/min per housing case. Total cost of the design was $300 for a dual pump set-up.