The cable guy

Once you’re hooked on rugged, high-quality machine-vision products, there’s no going back.

May 1st, 2007
Th 0705vsd Andywilson

Once you’re hooked on rugged, high-quality machine-vision products, there’s no going back.

Many years ago, a representative from Tektronix visited the engineering facility where I was working to show us the company’s latest CRT-based oscilloscope. After he twiddled numerous knobs and settings, we were all impressed with the unit’s 60-MHz bandwidth (yes, it was that long ago!).

During the demonstration, the sales representative picked up the ’scope and announced that he would show us the best feature of the unit. He dropped it! After powering back the unit, everything worked as easily as before. Needless to say, a purchase order was written the same day.

In developing machine-vision systems, integrators must evaluate numerous camera, lighting, lens, and PC-based products before deciding which OEM components should be used. Thus, the back-room engineering departments of these companies are often replete with products that have been used by their customers.

On a recent trip to one system developer, I was interested to see a number of different LED lighting components that the company had conveniently left out for all to see. Many of these had seen better days. In fact, many of them were in such poor condition that they could not be used again. From a careful examination of these products, it appeared many of them had one thing in common. The connecting wires that were supposed to supply power to the devices had become detached from the main body of the light. Often, rubber grommets were missing. In designs where no such grommets were used, bare wires could be seen!

Unfortunately, one trend was clear. Of all the lighting products that the company displayed, the ones that showed the most damage were built by domestic US companies. All of the products built by a certain overseas manufacturer were intact.

The overseas products were so carefully engineered that, in a moment of frustration, I picked up one ringlight and, to demonstrate the principle of centripetal force, twirled it around my head. Much to the shock and awe of my host, the product remained intact. “It all comes down to whether you drive a Ford or a Toyota,” my host explained after viewing my demonstration of a large mass in rotational motion.

More than price alone

Of course, there is more to choosing any product than price alone, especially in the machine-vision market. In the design of many systems, the lighting, optics, and cameras are placed on movable gantries or robots. In these systems, the interface between the cameras, lighting, and host computer becomes of prime importance.

However, instead of implementing industrial-strength connectors and cables into their products some lighting and camera companies are content with using off-the-shelf cables and standard Camera Link, USB, or Ethernet connectors and cables. No wonder that after several months it is not the camera or lighting in these systems that fails but the cabling and connectors that are used.

Low-cost lighting and camera products may seem like a bargain at the beginning of a project, but the cost of replacing products can make such choices foolish in the long term. Luckily, a number of cabling and connector companies have realized this and are producing rugged versions of standard products and cables. Although rugged cables and connectors are now readily available, designers of lighting, camera systems, and frame grabbers still need to incorporate them into their next generation of designs.

So, next time a lighting or camera vendor visits your facility, it may be prudent to show them some of the products that have failed for this reason. Then, after being assured that their product incorporates a rugged interface to stop this from occurring, you should, without hesitation, follow my example and see whether these products remain rugged after being subjected to large amounts of centripetal force!

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Andy Wilson
editor
andyw@pennwell.com

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