Ask The Search Engineer

Shed Some Light For Us, Search Engineer: We assemble five halogen lights on the roof racks of SUVs and want to run the wires on the exterior of the rack to save assembly time. I'm looking for a snap-on wiring duct to connect the lights, protect the wiring, and look good.—N.A. in New Mexico

Dear N.A.: Ah, the deer-in-the-headlights syndrome. How about flat conductor cable, such as used to run ac power under carpets to aisle counters? The product is available in heavy gauge (14 ga.) and is thin and flexible. Connection is via a pierce and crimp-style termination. Check with a local electrical power supplier.

Dear Search Engineer: We design various light wave guide (light tubes) for our products that direct and/or carry light from a source (LED, SMD, etc.) to some other point on the product. We need to find out how to successfully direct the light with design implementation and not guesswork.—P.G. in Louisville, KY

Dear P.G.: I can offer a couple suggestions. First, there are some fairly decent application notes by several manufacturers of LEDs and light pipes that could be helpful. One example is Application Brief I-003, "Light Guide Techniques Using LED Lamps" from Agilent's website (www.agilent.com). In addition, Chicago Miniature Lamp manufactures light pipes and can help with custom designs. Their website is (www.sli-lighting.com/cml/litepipe.htm).

Mr. Search Engineer: I need a highly reliable method to determine position on a linear vertically mounted track up to 50 ft long. My tightwad boss says that I can't spend much money.—B.B. in Mechanicsburg, PA

Dear B.B.: Linear transducers inputting into high-speed PLC ports may satisfy your penny-pinching supervisor. You will need some type of ratio device such as a cable and pulley assembly to give you the range you need. As one example, check out the Balluff catalog (www.balluff.com) which shows transducers up to 142 inches long. A 120-inch unit with a 5:1 ratio cable assembly could work, depending on the resolution and output required. There are also devices on the market for determining levels in tanks which could cover this range.

Hey, there, Search Engineer: At our plastic recycling company, we have a silo that holds polyethylene pellets (1/8-inch diameter) with a density of 35 lbs/ft 3. The silo has 11 welded rings. First ring is about 0.250 inch thick and the last top ring is less than 0.125 inch. Silo is 12 ft in diameter, 65 ft tall and the cone is at a 60° angle. On the bottom there is an airlock (rotary valve) used to discharge material by means of compressed air. Can we insert some pipes inside the silo?—J.J. in Arkansas

Dear J.J.: It appears that you are blending by using the pneumatic conveying line and blowing product from the bottom of the silo to the top. This is a very expensive and highly inefficient method! I suggest that you consider a ribbon blender or other suitable device for blending and storing the blended product in a smaller silo (day hopper) and refill as it is consumed.

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