The Linux Infrared Remote Control (LIRC) Project
It doesn't matter which way you install the resistor, but for all of the other parts, position matters. The capacitor has a minus sign beside one of the wires to identify which wire is which. The diode has a black line at one end to identify which end is which. When looked at from above, the 78L05 voltage regulator looks like a half moon, and where the wires are relative to the flat sides matters. There is a lens on one side of the infrared detector, and where the wires are relative to that lens counts. Numbers should be molded beside the pins on the DB9 connector.
Perforated board, or perfboard, is a wonder for hobbyist electronics work. It is a thin piece of non-conductive, heat tolerant plastic with holes drilled into it at 0.1" intervals. I use perfboard that has small copper rings bound to the board around each hole, which helps ensure the parts stay attached to the board.
The first step is to cut a piece of perfboard down to the right size. I used a small hacksaw for this job, but a Dremel or other small power-cutting tool can be used. We need a grid that is 4x5 holes, so cut along a line six holes in from one edge and five holes in from the other edge.
The first step is to attach the perfboard to the female DB9 connector. Place the board so that it is between the top and bottom row of pins and the copper rings are lined up with the solder cups for pins 6 through 9. Then, solder pins 6, 8 and 9 to the copper rings on the board.
You need to thread the wire from the end of the diode that does not have the black line on it through a hole (C1) in the perfboard and connect it to pin 7 in the DB9 connector. Trim the diode wire so it fits into the DB9 connector. When positioning the diode, remember that you don't have a lot of space above the perfboard, so keep everything close to the board. Clip the heat sink to the wire that goes into the diode and solder it into the DB9 connector. Wait a minute for things to cool down, and then solder the diode to hole C2. Run the wire from the black line end of the diode through hole D1, up to hole D2 and trim off the excess wire. Reposition the heat sink, solder hole D1 and then remove the heat sink.
The resistor goes in next. Place one end in hole D2 and the other in D3. Remember that you need to keep the resistor close to the board, but leave enough room for a wire to get into hole D4. The resistor has a high heat tolerance, so I skipped using the heat sink for this part. Position the resistor wire that comes in through hole D2 so that it ends by hole C2, and trim the excess. The resistor wire that goes into hole D3 should end by hole D4. Leave hole D3 alone for now, and solder hole D2.
Using a piece of wire trimmed from the diode, we make a little jumper. The wire needs to be bent so that one end goes into pin 5 of the DB9 connector, through hole B1 and then up, so it's just touching hole B4. Solder pin 5 in the DB9 connector and hole B1.
Now, put the voltage regulator into holes A2, A3 and A4. Remember to pay attention to the orientation of the regulator. Leave the wires on the component side long enough that you can clip in the heat sink and later fold the voltage regulator over, so it fits close to the board. Clip on the heat sink, solder holes A2, A3 and A4 and then remove the heat sink.
The next part is the capacitor. Pay attention to which wire is negative, and leave enough space for the heat sink and to fold the capacitor over. Clip on the heat sink, solder holes A3 and B3 and remove the heat sink.
Our second jumper comes next, made from a short piece of hook-up wire about 0.75" (2 cm) long. Trim the insulation off both ends and solder one end into pin 1 of the DB9 connector. The other end goes to hole D4. It may be a tight fit, and you may need to shift the resistor to fit things, which is why the resistor wasn't soldered earlier. Once the jumper is in place, solder the resistor at hole D3.
Finally, we come to the infrared sensor. You are going to have to do some test fittings to make sure that the leads are long enough so the sensor is just behind the hole in the plastic DB9 hood. This fitting also may require that you push the capacitor slightly to one side, out of the way. Once the length is adjusted, bend the wire that goes in though hole C4 so it goes across to hole D4. Clip on the heat-sink, solder holes A4, B4, C4 and D4 and remove the heat-sink.
Now you might want to take a minute to clean up. Apply some flux remover, per the manufacturer's instructions, to the solder side of the perfboard to clean away any flux residue left from the assembly.
The last construction job is to assemble the DB9 hood around the project. Once that's done, plug the interface into the serial port on your computer and start the machine. That finishes the hardware part of the project.
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