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What you need
These instructions show how to prepare a lightning sensor (control box and phototransistor cable).
You'll need to solder solder components and wires for this project. We'll provide guidelines for getting good solder joints, but we recommend that you have previous experience soldering on a PC board. With soldering, you can't make changes easily like you can with a breadboard. If you solder something in the wrong place, repair can be time-consuming.
Having the right tools will make the job easier. You'll need to provide your own. Here's what we recommend.
15-30 W soldering iron (with a new or pointed tip) and solder
Wire stripper (photo below)
A small diagonal cutter (photo below) makes it easy to trim the legs of the components after you solder them to the PCB, but other kinds of snipping tools such as scissors may work.
Needle-nose pliers (photo below) make it easier to handle small components, especially if you have big fingers.
A heat sink (photos below) protects heat-sensitive components while soldering.
A desoldering tool (photos below) helps in clearing solder from a hole. The cylindrical type works better than the bulb.
A magnifying glass is used to inspect solder joints.
A lighter or matches to shrink heat-shrink tubing
Wire cutters and
Be sure to solder in a well-ventilated area. Keep the tip of your soldering iron clean by wiping it against a wet sponge. Once the tip is clean, touch a bit of solder to the tip to tin it and improve heat conductivity. Inspect your solder joints to see if the solder flowed well to make good electrical contact. If it looks like the solder formed a bead, that's likely a bad joint and will not conduct. Reheat to flow the solder.
For the project box
Drill motor and bits to drill holes in the project box lid. Bit sizes are 3/32", 1/8", 1/4", and 5/16". (For metric equivalents in millimeters, multiply by 25.4.) You can substitute a 1/8" bit for the 3/32" one.
Hammer, punch (or nail), small round file
Wrenches or sockets to tighten components onto the project box
Aids to troubleshooting
If you need to troubleshoot problems with the circuit, it will help to have at least some basic skills in building and testing electrical circuits. These involve such things as testing for polarity and continuity, for examining solder connections, and for measuring voltages. In addition to such knowledge and exerience, having a continuity checker or multimeter and clip wires may be helpful.
Click here for a detailed, illustrated list of all the parts you'll need. You can use this list to identify the parts and make sure you have them all.
Soldering components to the PC board
If you don't have your soldering iron heated up, do that now, because you'll be soldering before long. You'll be doing some detailed soldering work, so an iron with a good tip will make it easier. In this part of the assembly, you'll solder to the PC board, shown in Figure 1 below. You'll insert components and wires from the front side of the board and solder them to the back side, which is copper-plated. Since the holes of the board aren't numbered, we've superimposed numbers on the front view of the board in Figure 2 and on the back view in Figure 3. The corresponding holes are highlighted. Orient the board with the word RadioShack at the bottom as shown in the photos. This is important since the board isn't symmetric when flipped vertically.
Position the 14-pin socket as shown in Figure 4 on the front of the board. Note that the notch in one end of the socket is at the bottom. Note also the lines which a and b, which are intended to point out the lack of top-bottom symmetry of the board.
Figure 1. Front and back views of PC board
Figure 2. Front of PC board, annotated
Figure 3. Back of PC board, annotated
Figure 4. Board with 14-pin socket positioned
Turn the board over and crimp the pins of the socket to hold it in place as shown in Figure 5 below. The outline of the socket is superimposed on the image to help guide positioning.
Solder the pins now. Completely fill each hole but be careful not to bridge the solder between holes. If you do, shake any excess solder off the tip of the iron and draw it along the board through the bridge to remove it. Several tries may be required. If this doesn't work, you may need to use a desoldering tool. The completed solder job is shown in Figure 6.
Add the 100-ohm resistor (shown to the right) to the board. Figure 7 shows the position of the resistor the board. Bend the legs down and push them through holes 3 and 5. (Refer to Figures 2 and 3 above as needed for hole numbering.) Figure 8 shows the resistor legs extending from the back of the board. Solder the legs to the back of the board and clip them off.
Add the 0.01-μf capacitor into the board through holes 11 and 12 as shown in Figure 9. Solder the legs to the back of the board and clip them. Figure 10 shows all the soldered connections so far from the back of the board.
Figure 5. Socket pins are shown crimped from the back
Figure 6. Soldering of the socket completed
Figure 7. Jumper wire ready to insert into R5
Figure 8. Resistor legs from the back of the board
Figure 9. Capacitor added to the board
Figure 10. Soldered connections so far
Cut two white wires and one yellow wire to add to the board in the locations shown in Figure 11 below. The following table gives the holes between which the wires are connected. Solder the wires on the back of the board.
Refer to Figure 11
Hole to Hole
1 to 6
7 to 8
2 to 9
There's one more wire to add to the board. Cut a red wire to extend from hole 4 to hole 10 as shown in Figure 12. Then solder it to the back of the board.
You won't be soldering to the PC board again until after you've added components and wires to the lid of the project box. However, you can insert the ICs now. Start with the 555 timer. Figure 13 shows the orientation that the 555 timer will have in the socket. Note the notch at the bottom. Seat the pins of the IC firmly into the lower 8 holes of the socket as shown in Figure 15.
The PS2501 optocoupler is shown in Figure 14 with the orientation it will have on the board. There's a light-colored dot beside the lower right pin. Seat the optocoupler in the socket in this orientation. Use the upper 4 holes of the socket as shown in Figure 15. This will leave 2 empty holes separating the two ICs.
Figure 11. White and yellow wires added to the board
The template is sized to fit within the underside of the project box lid (that is, on the interior side of the box). Position the template inside the lid as shown in Figure 16 below. Then use a nail or punch to mark the positions of the centers of the holes to be drilled.
Remove the template and drill the holes. We recommend drilling small pilot holes first, for example, 3/32" or 1/8". The plastic has a tendency to grab the bit, so hold the plastic securely. We've found that spade bits work best for drilling the 1/4" and 5/16" holes. Figure 17 shows th inside of the box lid after the holes are drilled, while Figure 18 shows the reverse view from the outside of the lid.
Figure 16. Template placed in underside of project box lid
Figure 17. Inside of project box lid after holes drilled
Figure 18. Outside of project box lid after holes drilled
The completed assembly of all components on the project box lid is shown in Figures 19 and 20 from below and above, respectively. Refer to the Parts List for help in identifying components. Here is information on mounting the parts:
Remove the nut from the 3.5mm stereo jack (black plastic case), insert the jack through the box lid from below, and screw the nut back on. Needle-nose pliers can be helpful in tightening the small, round nut.
Repeat the previous step for the 3.5mm mono jack (cream-colored plastic case).
The two switches have a retaining ring with a key tab, a washer, and a nut. Remove all three and then insert the switch from below. Orient the slot on the threads to be on the same side as the 3/32" key hole. Then slip the retaining ring on so that the key tab slips into the 3/32" hole. Slip on the washer and nut and tighten.
The potentiometer has a key tab on the body of the pot. Remove the washer and nut from the pot, slip it in from below and orient it so that the key tab passes up through the 1/8 " key hole. Then put on the washer and nut and tighten.
Figure 19. Underside of lid with all parts mounted
Figure 20. Top view of lid with all parts mounted
The two jacks are shown in Figures 21 and 22 below to help in wiring the lugs of the jacks correctly. The numbering on the lugs is the same as will be used below in the instructions. Make connections as indicated below but wait to solder until later.
Cut a section of yellow wire to connect between the left lug of the lower switch and lug 2 of the 3.5mm stereo jack as shown in Figure 23.
Cut two sections of white wire for these connections: a) center lug of the lower switch to lug 1 of the 3.5mm stereo jack, b) left lug of the upper switch to lug 1 of the 3.5mm mono jack. See Figure 24.
Connect the 1-kΩ resistor from lug 3 of the 3.5mm mono jack to the left lug of the pot. See Figure 25. You'll need to clip the legs of the resistor to shorten it so that it will fit.
Now you're ready to make connections between the lid and the PC board.
Figure 21. 3.5mm mono panel jack with lugs numbered
Figure 22. 3.5mm stereo panel jack with lugs numbered
Figure 23. Yellow wire connected
Figure 24. White wires connected
Figure 25. 1-kΩ resistor connected between mono jack and pot
Here are some more tips about soldering in addition to those given previously.
Soldering the switches: Don't hold the soldering iron on the switch lugs too long, as the plastic can melt and break the internal contacts.
Soldering the 3.5mm jacks: The lugs on these jacks bend and break easily. Go easy on them.
About cold solder joints: If you don't heat the metal before soldering the wire, the solder may not bond with it and you can get an open circuit. You can't necessarily tell by looking that you have a cold solder joint. The best approach is prevention by using good soldering techniques. Hold the tip of the soldering iron flat against the metal surface that you're soldering to. Touch the solder to the metal nearby rather than to the soldering iron. When the metal is hot enough, the solder will flow. Flow enough solder on the connection to fill the hole and cover the connection, but don't leave the soldering iron on the metal any longer than it takes to flow the solder. Examine the connection under a magnifying glass. If the solder beaded up, you may not have a good connection.
Cut and strip the ends of 2-inch sections of these five colors of wire: red, black, white, yellow, blue. These will be the wires that connect the lid to the PC board. Connect the 5 wires to the locations shown in Figure 26 below. The following table lists the connection points.
Refer to Figure 26
lug 1 of 3.5mm stereo jack
lug 3 of 3.5mm stereo jack
lug 3 of 3.5mm mono jack
center lug of pot
left lug of upper switch
Figure 26. Jumper wires added to the lid
Figure 27. All connections except center lug of pot soldered
You can now solder all the connections except for the one circled in yellow in Figure 27 above. Leave the center lug of the pot unsoldered, since you'll be connecting the red wire from the battery holder to that lug later.
The holes into which the 5 jumper wires will be soldered to the PC board are indicated with the numbers 13 - 17 in Figures 28 (front of board) and 29 (back of board). Refer to these as needed when soldering the wires to the board. The completed connections are shown in Figure 30.
Figure 28. Connection points numbered on front of PC board
Figure 29. Connection points numbered on back of PC board
Figure 30. Jumper wires connected to PC board
Figure 31. Battery holder wires threaded through side of box
Figure 32. Top view of battery holder wires threaded through side of box
Figure 33. Battery holder seated on side of box and knot tied in wires inside
The last connections to make are the two wires of the battery holder to the box lid. First, drill a 1/8" hole in the approximate location shown in Figure 31 above. Stick one of the hook and loop strips to the same side of the box as the 1/8-inch hole, and stick the other piece of tape to the bottom of the battery holder. Thread the two wires through the hole into the box. See Figure 32 for a different view.
Stick the battery holder onto the side of the box. A view looking down into the box is shown in Figure 33. Tie an overhand knot in the red and black wires inside the box.
Figure 34. Knot tightened to serve as strain relief
Figure 35. Connection points of the battery holder wires to the lid
Figure 36. Closing the box
Figure 37. Lid of box with knob and labels
Tighten the knot and work it up toward the hole as shown in Figure 34 above. The knot serves as strain relief so that the battery holder wires won't be able to be pulled loose from connections that will be made inside the box.
Solder the battery holder wires to the points circled in yellow in Figure 35. The red wire connects to the center lug of the pot, and the black wire connects to the middle lug of the upper switch.
Position the PC board below the lid and lower the assembly into the box as shown in Figure 36. You may wish to wait to screw the lid down until after you've completed testing.
Now you can put the knob on the pot and the labels on the lid. Turn the pot counterclockwise as far as it will go.Then tighten the set screw. Figure 37 shows the knob mounted and turned to its halfway setting. The labels have also been added.
This completes the box assembly. The last thing to do before testing is to assemble the phototransistor cable.
Assembling the phototransistor cable
Strip 2 inches of the gray insulation from one end of the 2-conductor cable. Cut two 1-inch sections of the smaller diameter (3/32 in) heat-shrink tubing and slip one piece onto each wire. Then strip the individual red and black conductors back by 3/4 inch as shown in Figure 38 below.
Next identify the legs of the phototransistor. It has three legs, but only two are used. Hold the photransistor
so that you are looking at the dome with the
legs pointed away from you and the tab on the case pointing
up as shown in Figure 39. The leg nearest the tab is the emitter and will be
connected to the black conductor. The leg to the right
of the tab will connect to the red wire. The last leg
can be bent outward and will not be used.
red wire onto the positive leg as shown in Figure 40.
Twist the black wire around the negative leg and solder both connections. See Figure 41.
Slip the heat-shrink tubing around the solder joints and then shrink the tubing with a heat source such as the flame of a match or lighter. The result is shown in Figure 42.
Bend the third, unused leg of the phototransistor inward toward the other two. Now wlip the section of 3/16-in heat-shrink tubing over the gray cable from the end opposite the phototransistor. Slip the tubing all the way up to the base of the phototransistor to cover all the legs. Heat the tubing to shrink it into place. The result is shown in Figure 43.
Figure 38. Stripping the wires and slipping on the heat-shrink tubing
Figure 39. Phototransistor viewed looking down at the dome
Figure 40. Red wire wrapped around the positive leg of the phototransistor
Figure 41. Both legs of the phototransistor soldered
Figure 42. 3/32-in heat-shrink tubing shrunk in place
Figure 43. 3/16-in tubing shrunk in place
Next you'll add the 3.5mm mono connector to the other end of the cable. Remove the black jacket from the connector and slip it over the cable as shown in Figure 44 below. Then strip 1/4 inch of the gray insulation from the end of the cable. Strip the red wire about 1/8 inch and the black wire 3/16 inch.
Thread the red wire through the shorter lug and the black wire through the other lug as shown in Figure 45. Don't crimp the tabs around the gray insulation until after soldering. The soldered connections are shown in Figure 46.
Figure 44. Preparing the cable for the 3.5mm mono connector
Figure 45. Connecting the red and black wires to the lugs of the plug
Figure 46. Completed soldering
Figure 47. Tabs crimped over the cable
Figure 48. Completed plug
Figure 49. Completed cable
Now you can crimp the tabs. See Figure 47. Clip any stray wires that could create a short.
Screw the jacket on to complete the connector as shown in Figure 48. The completed cable is shown in Figure 49.