Assembly Instructions for the Lightning Trigger (LT2)
Building the control box
Parts guide (opens in new tab or window)
Operating instructions (opens in new tab or window)
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These instructions show how to prepare a lightning trigger (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
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.
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.
- 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 Color
Hole to Hole
white 1 to 6 white 7 to 8 yellow 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||Figure 12. Red wire added to board||Figure 13. Orientation of 555 timer|
|Figure 14. PS2501 optocoupler||Figure 15. Both ICs seated in the socket|
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 Color
black lug 1 of 3.5mm stereo jack blue lug 3 of 3.5mm stereo jack yellow lug 3 of 3.5mm mono jack red center lug of pot white 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.
- 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.
- 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.
- Twist the red wire around the longer leg of the phototransistor and the black wire around the other leg as shown in Figure 39.
- Solder the two legs as shown in Figure 40. You may wish to use a heat sink on each leg as your solder or else solder quickly to avoid excessive heat build up.
- Slip the heat-shrink tubing over the bare wires. Use a lighter to shrink the tubing. See Figure 41 above.
- Slip the 3/16-inch heat-shrink tubing over the cable from the opposite end. Cover the section below the phototransistor and shrink the tubing in place as shown in Figure 42.
- 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 43 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 44. Don't crimp the tabs around the gray insulation until after soldering. The soldered connections are shown in Figure 45.
- Now you can crimp the tabs. See Figure 46. Clip any stray wires that could create a short.
- Screw the jacket on to complete the connector as shown in Figure 47. The completed cable is shown in Figure 48.
Go on to the operating instructions.