When Resolution Air, Ltd. (Cincinnati, OH) started researching components for their new line of Miniature Proportional Pinch Valves (MPPV), they looked for ruggedness and quality first. The valves were being designed to deliver tight specifications for high-resolution flow control for integration into portable and handheld equipment in a variety of key industries, including bio-chemical, food and beverage, and healthcare. The valves are used to pinch a fluid-filled, low durometer tube with varying amounts of pressure to regulate the flow of the fluid (liquid or gas) through the tube. The device was designed to incorporate a stepper linear actuator (stepper motor and lead screw) and a custom piston in a miniature aluminum valve body. The company manufactures the patented valve in-house, but purchases a controller to accompany their demonstration kits.
Resolution Air searched for a controller that would minimize the time and complexity involved in these necessary and important steps of the evaluation process. “Our extensive research for the right component led us to the discovery of the StepperStick controller, manufactured by AllMotion,” said Brad Thompson, Owner and Chief Engineer on the project. The StepperStick eliminated the complexity of the control system by simplifying the wiring, the power supply requirements, and the programming needed for evaluation.
The StepperStick is delivered with a wiring harness, which connects to the stepper motor mounted on the MPPV. The device then plugs into the USB port of a computer. This USB connection is used to provide communications with Allmotion’s Windows-based programming language. The computer also provides the power needed for both the controller and the stepper motor, which eliminates the need for an external power supply to drive the valve specifications.
The StepperStick provides up to 0.5 amps of current to the stepper motor. The device also has a current adjustment, which allows the customer to reduce the current output to match the valve’s requirements (0.385 watts). Plus, the MPPV only requires power to adjust position, not maintain position, therefore creating even greater power savings to the user.
The StepperStick is housed in a USB Stick measuring only 2 x 1 x 0.5-in. thick, and is a fully intelligent stepper motor controller and driver capable of moving bipolar stepper motors. The device works on any stepper motor that is 1.7-in. or smaller (size 17 or smaller). The StepperStick appears as a Virtual Com Port when plugged into a computer, and commands are easily sent via ASCII text from any serial terminal program or from AllMotion’s EZCommander application. The StepperStick is also capable of standalone operation with no connection to a PC (external power supply required). It can easily be set to execute a preset string of commands upon power up. Commands include nested loops as well as execution halt pending a switch closure. Additional features of the StepperStick include full, half, quarter, or eighth step bipolar control; pre-wired OptoSwitch inputs; industry standard communications protocol; fully programmable ramps and speeds; and four digital I/O and two ½ amp power On/Off drivers.
The MPPV has a linear travel of 0.005-inches per step, which translates into extremely high-flow resolution, as well as high sealing-force of up to 16 pounds of thrust at 100 steps per second. The valve also features a locking lead screw. Standard sized pinch valves accommodate 1/8-inch, ¼-inch, 3/8-inch, and ½-inch OD tubes. The miniature size of the device creates an excellent opportunity for integration into portable equipment.
Resolution Air, Ltd.