Tech Directions - December 2007 - (Page 15)

op-amps requiring an external capacitor for stabilization, the wiring capacitance existing between the DIP socket’s pins is adequate for testing. When the right LED is lit, the output is positive and when the left LED is lit, the output is negative. If the two LEDs toggle, the op-amp is good. The op-amp is bad only if one LED glows or if neither LED glows. Parts List Item 01 01 03 04 05 06 07 08 09 10 11 12 13 Qty. 1 1 1 pkg. 1 or 1 pkg. 2 1 pkg. 1 pkg. 1 pkg. 1 pkg. 1 1 pkg. 2 1 1 Description Enclosure, 270-283, Radio Shack Perfboard, 276-1395 Push-button switch, NO, 275-1547, Radio Shack 8-pin DIP socket, WWICS-8, All Electronics 8-pin DIP socket, 276-1995, Radio Shack LED, green, 276-022, Radio Shack R1, 2.2 kΩ, 272-1325, Radio Shack R2, 22 kΩ, 272-1339, Radio Shack R3, 220 kΩ, 272-1132, Radio Shack R4, 220 Ω, 272-1313, Radio Shack C1, 0.1 μF capacitor, 272-135, Radio Shack Battery clips, 270-325, Radio Shack 9 V batteries Small sponge Small piece of cardboard or business card Building the Checker 1. I suggest first building the opamp checker on a proto-board so it resembles the op-amp checker shown in Photo 1. This will allow you to see and physically hook up all necessary components of the circuit, as well as better understand the op-amp checker’s theory of operation. 2. Refer to the schematic diagram (Fig. 1) as you build your circuit. The parts needed to build the opamp checker are, for the most part, available at Radio Shack and are listed on the parts list. At this stage of the project, you will not need the 8-pin socket or the enclosure. 3. After you have successfully built your op-amp checker on your proto-board, tested it, and proven it to be lab worthy, construct the opamp checker that looks like the unit shown in Photo 2. Do not disassemble your proto-board circuit. If there is a wiring error in the newly built op-amp checker, having a unit that works will be helpful. 4. Refer to the panel layout drawing (Fig. 2). Carefully measure and mark the perfboard per the indicated dimensions. Double-check your measurements, then carefully cut the perfboard. 5. Place the cut perfboard on top of the plastic box. It should fit nicely—if not, fix it. Use a piece of medium grit sandpaper to smooth out any rough edges on the perfboard. 6. Next, carefully measure and, with a pencil, mark the locations to be drilled on the perfboard for the 8-pin socket as shown on Fig. 2. Double-check your measurements then carefully drill the eight holes Radio Shack: 800-843-7422; All Electronics: 800-826-5432 Photo 2—Completed op-amp checker 3.2 #55 each 0.1" apart 8 places C 0.8 0.8 2.0 C 1.0 A 1.05 1.50 C A hole—Drill with #J B hole—Drill with #55 C hole—Drill with #30 B 0.9 0.8 C 0.25 0.25 Typical, each corner Fig. 2—Panel layout drawing www.techdirections.com ELECTRICITY/ELECTRONICS 15 http://www.techdirections.com

Table of Contents Feed for the Digital Edition of Tech Directions - December 2007

Tech Directions - December 2007 Technically Speaking Contents Direct from Washington The News Report Technology Today Technology's Past Mastering Computers Is This Op-Amp Any Good? Lab-Built Checker Removes All Doubt Here Comes the Sun! Residential Solar Systems Add Up to Savings Pinhole Cameras—For Science, Art, and Fun! Poster Project Maps Out Design Process Gifts for Geeks E-gallery More than Fun

Tech Directions - December 2007

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