Even the highest quality metrology equipment can’t truly shine without a motion controller that functions with the same level of precision. H2Optx’s mPAT LAB multiplexed Raman and Optical microscope system needed a motion control platform that was easy to use and would allow quick integration during the prototyping stage of the design cycle. H2Optx Inc. provides the pharmaceutical, food and fine chemical industries with multi-spectral, online measurement devices. The devices can be used in end product situations or as a device within a larger, more complex laboratory or production system.
Because H2Optx is a small team of specialists working to develop products for highly specific industries, its ability to integrate components for a particular system quickly and efficiently is important. Specifically, its ability to move samples and then do a detailed scan of the samples depends on complex underlying motion control capabilities.
The mPAT incorporates a laser ScanHead as well as an optional material handling accessory, such as either the company’s Pillerator or Powderator product. That means that a controller must work right out of the box, and the software must be easy to integrate into pre-existing system components. In addition, the controller had to have high levels of overall integration (like a four channel controller in a single, compact, printed circuit board). Raman microscopes are laser-based devices that are used to identify and quantitate samples by measuring and evaluating the scattering properties of materials.
The underlying capabilities of a Raman Scanning Microscope are enabled by the ability to move an optical block that houses a laser, microscope, digital camera and spectrometer interface together on a three-axis stage. The three axes are driven by accurate and repeatable linear stepper motor actuators. The system is controlled using a personal computer over a standard USB port. Therefore, the H2Optx needed a controller that was USB based. Plus, it needed to handle multiple axes simultaneously. “The only solution we found that would meet all of our needs was the AllMotion EZ4AXIS controller,” said company spokesperson Scott Tandy.
To accomplish the scanning function, the controller had to have a flexible enough interface to allow it to execute pre-programmed actions on its own, without the PC involved. At 2.25 x 2.25 x 0.6 in. (57 x 57 x 15 mm), the EZ4AXIS is one of the smallest controller/drivers on the market—and one of the most powerful in its size. It is a four-axis position controller with built-in power drivers. It also incorporates dual encoders as an integral part of the package.
H2Optx required a controller with at least 16 microstep resolution and 1 A drive current. The controller provided these capabilities for four outputs (one more than was needed). In addition, the design called for the use of hardware limit switch capability, something that came as part of the controller package.
The H2Optx design team was also happy with the way the controller easily integrated with other components of the system. Its flexibility helped make interfacing easier. Each independent axis functions through a 1 A (2 A peak) PWM chopper driver.
According to Tandy, “AllMotion provided all of the motion control capabilities we needed in a compact package. We integrated the EZ4AXIS directly into our ScanHead design using it as a daughter board to our main printed circuit board. This allowed us to use all of the features of the controller, but pick and choose the connectors and interconnects that we wanted for our form factor.”
As far as ease of use was concerned, H2Optx engineers found that the EZ4AXIS’ software was based on industry standard serial interfaces. Thus, direct interaction with the product was easy to incorporate during the investigation and early prototyping phases of the design—all while using the software application that AllMotion provided. “For the final product integration into our Microsoft C#/.Net environment, the serial port interface meant that there were no additional software modules to integrate into our mPAT system software,” Tandy said.
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