Servo controller dispenses precisely, rapidly

Syringe pumps support automated sampling and analysis by quickly and accurately dispensing tiny volumes. The smaller the drop, the smaller the sample, which lets users increase the array size and use faster speeds to deliver greater throughput. Much relies on implementing the right controller, one that is reliable, accurate, and ideally off- the-shelf, so if equipment fails, it can be quickly repaired or replaced.

Robert Irwin, principal engineer for Parker Hannifin Corp.’s Precision Fluidics Division in Hollis, New Hampshire says, “I needed a controller that provided the high resolution and high-speed sampling rates for our syringes, which are designed to be used hundreds of thousands of times in an analytic procedure in the life sciences.”

With a quick response time, including a fast acceleration and fast stop, Union City, California-based AllMotion’s EZSV17WV servo motor controller met the needs. Used in conjunction with an optical rotary encoder for feedback, the servo drive replaced an older one used for the syringe pump.

“At first, the benefit we were excited about was its intuitive motion control language and the amount of support available for programming,” Irwin says.

When explaining the operational language to customers, Irwin found the straightforward ASCI coding provided a quick learning curve. Multiple available inputs added to its appeal. If a customer was looking for a single action, a switch input is available – for analog use (mechanical, optical, resistance), a sensor input.

Whether aspirating or dispensing, the 1.6" x 1.6" servo motor controller provides room for other components. Designed to promote rapid implementation of brushless DC motors or brushed DC motors in automation products, the EZServo series intelligent controllers require little to no tuning. The controller’s default proportional-integral-derivative (PID) values are robust and stable with most motors. A single 4-wire bus – two power wires, two communications wires – links up to 16 motors in a daisy chain. With erasable, programmable read-only memory (EPROM) storage, the controller runs from startup without being connected to a computer, allowing stand-alone operation.

“For our application, AllMotion provided a simple converter for use to go from RS485 to RS232,” Irwin says.

Other options include USB to RS485 converters and a size 17 enclosure.

Overall, the EZSV17WV servo controller, with closed-loop feedback, was the right choice for Parker Hannifin’s syringe application. It provides the speed and reliability necessary in the life sciences sampling and analytical world, handles very small samples, is easy to program, and its small size is a bonus to engineering teams.

www.allmotion.com

Parker Hannifin Corp., Precision Fluidics Div.
www.parker.com/precisionfluidics