Tech Directions - February 2008 - (Page 22)

diagram (Fig. 2), build your circuit. At this stage, you will not need a 5-pin socket or the enclosure. 2. After you have successfully built your BJT checker on your proto-board, tested it, and proven it lab worthy, it is time to construct the BJT checker that looks like the unit shown in Photo 2. Do not disassemble your protoboard circuit. If there is a wiring error in your newly built BJT checker, having a unit that works will help you. 3. Refer to the panel layout drawing (Fig. 3). Carefully measure and mark the perfboard. Double-check your measurements, then carefully cut the perfboard. Place the cut perfboard on top of the plastic box. It should fit nicely. If not, fix it. Using medium-grit sandpaper, smooth any rough edges on the perfboard. 4. Carefully measure and mark the locations to be drilled on the perfboard for the two push-button switches as shown in Fig. 3. Double-check your measurements, then carefully drill the two holes using a #J drill bit. If you do not have a #J drill bit, use a drill bit that will allow a 1/4" thread to pass through the hole. Photo 2—Completed checker mounting screws will be inserted through the perfboard and attach to the plastic enclosure. Mark each spot with a pencil. Double-check the measurements and if all is OK, drill the holes using a #30 drill bit. 7. Attach the two push-button switches to the perfboard. Viewing from the outside portion of the perfboard, install the black button switch at the left, then install the red button switch at the right. Using your fingers, snug the hex nuts down. 8. Referring to Fig. 1, solder a piece of solid wire (about #24 AWG or so) between the inside pins of the two switches. Insert the 5-pin socket into the perfboard. Solder jumper wires (about #24 AWG or so) to the appropriate pins of the 5-pin socket. 9. Referring to Fig. 3, insert the left and right LEDs. Make sure the flat side of each LED (cathode) is closest to the socket. Referring to Fig. 1, solder the appropriate leads of the LEDs to the 5-pin socket’s outer pins. 10. Referring to Fig. 1 and Photo 3, solder one side of each of the two 1 kΩ resistors to the unconnected pins of the LEDs. Solder the other ends of the resistors to the unconnected pins of the two push-button switches. #24 AWG Socket LED 1 Flat side + - i + - #24 AWG LED 2 Flat side C1 1K 10 M 1 μF R1 R3 Red Battery clip 5. Do not attach the two push-button switches at this time. Get the 5-pin socket, and, referring to Fig. 3, carefully determine where the 5-pin socket will be inserted into the perfboard. Locate where each individual pin of the 5-pin socket will be inserted, and mark these locations with a pencil. Using a #55 drill bit, drill the five holes. 6. Insert the 5-pin socket into the perfboard. The socket should fit snugly. Do not mount the 5-pin socket at this time. Next, find the locations where the four 22 techdirections 1K R2 Black PB NPN S1 Red PB PNP S2 #24 AWG Black 9 V battery + R2 i C1 1 μF S2 PNP LED 2 1K Fig. 1—Wiring diagram R1 + 1K LED 1 R3 10 M S1 NPN Fig. 2—Schematic ◆ FEBRUARY 2008

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Tech Directions - February 2008 Technically Speaking Contents Direct from Washington The News Report Technology’s Past Technology Today Mastering Computers How Engineers Engineer—Lessons from My First Big Engineering Project Tips on Creating Complex Geometry Using Solid Modeling Software Press to Test—Shop-Built BJT Checker Is Easy Cable Television Technician International Technology Education Association Conference—Teaching TIDE with Pride Professional Development Opportunities Product Central Free for the Asking More than Fun

Tech Directions - February 2008

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