Power over Camera Link enables smaller systems
By Ann R. Thryft, Contributing Technical Editor -- Test & Measurement World, 4/1/2009 2:00:00 AM
A little more than two years ago, the AIA (Automated Imaging Association) ratified two extensions to the Camera Link standard: the PoCL (Power over Camera Link) interface and the mini-Camera Link connector. Since then, user demand has risen for these interfaces, especially PoCL, in cameras and frame grabbers used in machine vision. Both help facilitate smaller cameras by reducing the size of the camera's back panel.
 In a Camera Link connector, pins 1, 13, 14, and 26 are connected to an inner shield to provide an isolated internal ground. In a PoCL connector, pins 1 and 26 are reassigned to carry +12-V power. Courtesy of JAI. |
PoCL helps reduce the number of necessary cables, and the number of connectors on the back of a camera, by powering a camera directly through the interface. “The interface eliminates the need for a separate power supply,” said Steve Kinney, JAI's director of technical pre-sales and support, who also chairs the AIA's Camera Link committee. “It provides a clean, one-cable solution that fits more easily into crowded spaces, saves on cabling costs, and avoids problems caused by cables rubbing together.” This is important in repetitive, space- and weight-critical environments such as semiconductor and electronics inspection, where cameras repeatedly move very quickly over the surface of a board or wafer.
Since PoCL provides only 4 W, users of high-performance cameras will still need external power supplies. But many smaller cameras can be powered with PC-based frame grabbers using PoCL, said Kinney. “In the Camera Link standard, there are four redundant pins assigned to ground, one on each corner of the connector. In Power over Camera Link, two of those pins are reassigned for power.”
The size of the back plate in most frame grabbers accommodates a maximum of two Camera Link connectors, said Kinney. But the mini-Camera Link connector, which is pin-for-pin compatible with the original, is only half the width and half the height of it, so four can fit in that same space.
“We see Camera Link and GigE Vision as the two dominant vision standards in the near future,” said Kinney. Improvements to PoCL are in the works: Although the current implementation only provides for 4 W over a single base Camera Link configuration, in theory it is also possible to provide 8 W over a medium or full configuration. Members of the Camera Link committee are currently working on proposals to do exactly that.
Hardin, Winn, “Camera Link 1.2: Power in Small Spaces,” Automated Imaging Association, February 28, 2007. www.machinevisiononline.org/public/articles/details.cfm?id=3072.
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