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Assembly and Operating Instructions for Kits


Instructions for Building the Sound Trigger 2 (ST2)


Assembly instructions for other kits


Control side Sensor side






For individual photos of the parts supplied in the kit, see the Parts List.


If you would like to refer to a circuit schematic while you work, download one here.


In the instructions below, click on any image for a larger view. (In order to open the image in a new tab or window, right click and select open in new tab or window.)



Tools that you'll need


Having the right tools will make the job easier. You'll need to provide your own. Here's what we recommend.

  1. 15-30 W soldering iron and solder
  2. Wire stripper (photo below)

  3. A small diagonal cutter (photo below) makes it easy to trim stray wires, but other kinds of snipping tools such as scissors may work.

  4. Needle-nose pliers (photo below) make it easier to handle wires, especially if you have big fingers.

  5. A magnifying glass is useful to inspect solder joints.

  6. A lighter or matches to shrink heat-shrink tubing, if the project requires it. (The ST2 kit does not require this.)

  7. A drill motor and these drill bit sizes: 3/32, 1/8, 1/4 in

  8. Rubber or contact cement to affix the label to the project box lid

  9. Hammer and a pointed instrument such as a large needle or a punch
  10. Stencil or razor knife and a straightedge
  11. Hole punch such as that used for punching paper for binders
  12. Mild solvent such as denatured or rubbing alcohol and soft, clean cloth
Wire strippers diagonal cutter needle-nose pliers
Wire stripper Diagonal cutter Needle-nose pliers


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.


Soldering Components to the PCB

About the printed circuit board (PCB)


Note the photos of the PCB below. In the instructions, we'll use the terms top side and under side to refer to the two sides of the PCB. This will be important, as some components are mounted on the top side and soldered to the underside, while one component (the piezo disc) is mounted on the under side and soldered to the top side.

Top side of the PCB Under side of the PCB


Step 1. Adding the resistors to the PCB


Photo 1a: Start with the PCB and one of the 1k resistors (see photo to the right). The resistance value is indicated by the sequence of band colors. Brown-black-red indicates a 1k resistor (brown = 1, black = 0, red = 00). Insert the legs of the resistor into the location labeled R1 on the PCB. Note that the resistors aren't polar and can be placed in either of the two possible orientations.


Photo 1b: Solder the legs to the back side of the PCB and then clip off the excess. The completed solder connections, circled in yellow, are shown in the photo.


Photo 1c: There are 3 remaining resistors. Solder these as follows: 100k (brown-black-yellow) into position R2, 1k (brown-black-red) into position R3, 5.1k (green-brown-red) into position R4.


Photo 1a Photo 1b Photo 1c


Step 2. Adding the semiconductors to the PCB


Photo 2a: The transistor (PN2222A) and SCR (EC103D) look alike. Be careful not to interchange them. Insert the transistor in the location labeled Q1 on the PCB. Note that the flat side of component aligns with the flat side of the outline on the PCB. In a similar fashion, insert the legs of the SCR into the location Q2 on the PCB. Push the components down to seat them securely.


Photo 2b: Solder the legs on the underside of the PCB. Try to solder quickly, as the components may be damaged by overheating. You may wish to wait a short time after soldering one leg before moving to the next. The completed assembly is shown in Photo 2b.

Photo 2a Photo 2b


Step 3. Adding the piezo disc to the PCB


Photo 3a: Note the three holes labeled G, F, and M inside the large circle on the PCB. These are for the corresponding pins on the piezo disc. Note, however, that the piezo disc will be inserted on the under side of the PCB and soldered on the top side. Photo 3a shows the top side of the PCB with the pins of the piezo disc inserted. The pins are circled in yellow. Solder the pins now.


Photo 3b: The completed PCB assembly is shown from the under side with the piezo disc mounted.

Photo 3a Photo 3b


Preparing the Lid of the Project Box and Affixing the Label

Step 4. Drilling the lid


Photo 4a: Place the drilling template in the under side of the project box lid. Using a hammer and a sharp, pointed instrument such as a large needle or a punch, mark the centers of the 7 holes on the template.


Photo 4b: Remove the template. Then drill 3/32-in starter holes at each of the 7 locations that you marked. Then drill the holes to the sizes as marked on the drilling template.

Photo 4a Photo 4b


Step 5. Adding the label


Photo 5a: Trim around the black border of the lid label. A stencil or razor knife with a straightedge will help to get straight cuts, but sharp scissors will also serve.


Photo 5b: Pull the backing off one of the laminate sheets, and lay the sheet, sticky side up, on a table. Carefully place the lid label, label side down, onto the sticky side of the laminate sheet. In order to avoid getting air bubbles, apply the shorter edge of the label first and gradually push it down onto the laminate with a finger.


Photo 5c: Remove the backing from the other laminate sheet and carefully apply it, sticky side down, to create a sandwich of the two laminate sheets with the label in the middle. Use the technique described above to avoid getting air bubbles. When the laminate is in place, rub a finger over the laminate and around the edges of the label to ensure a good seal. Finally, use a stencil or razor knife or sharp scissors to trim the excess laminate from around the label. The completed label with laminate applied and trimmed is shown in Photo 5c.


Photo 5d: Use a hole punch to punch out the two 1/4-in holes on the label. If you don't have a hole punch, the point of a sharp knife can be used to carve out the holes. Ragged edges will be covered later when the components are mounted.


Photo 5e: Cut the 2-in section of plastic tubing into two 1-in pieces. Align the label with the two 1/4-in holes in the top of the lid of the project box. Then push the two pieces of tubing through the holes to force alignment. Next, use a sharpened pencil to push through the 1/8-in hole. Don't worry that these holes aren't cleanly cut out. When you push bolts through the holes later, any raggedness around the edges will be covered.


Photo 5f: Now it's time to glue the label to the top of the lid. First remove the plastic tubing and label from the lid. Then use rubber cement or other repositionable adhesive for this. Spread the adhesive over the lid as shown in Photo 5f. Next spread the adhesive over the under side of the label (not shown). Put the label in position on the lid and use the plastic tubing and the point of a pencil as before to make sure that the holes are aligned. Flatten the label by rubbing a finger over it and hold in position for a minute or so to insure adhesion. Then carefully remove the plastic tubing to avoid shifting the position of the label. Any glue that extends beyond the edge of the label can be rubbed off with a finger. If there is glue smeared on the label that can't be rubbed off, use a mild solvent such as denatured or rubbing alcohol and a soft, clean cloth to clean the label. Finally, place the label under a stack of books or other weight to press it for a few hours.


Photo 5g: When completed, the lid with label should look like Photo 5g. Check the under side to see if portions of the label overlap the two 1/4-in holes. If so, use a stencil knife, razor, or knife blade to trim the label back to the boundaries of the hole. This will make it easier to insert components later.


Photo 5a Photo 5b Photo 5c Photo 5d
Photo 5e Photo 5f Photo 5g  


Adding Components to the Lid of the Project Box

Step 6. Adding the switch and the LED


Photos 6a-c: In Photo 6a showing the switch, notice the ring with the tab pointing toward the base of the switch. When you mount the switch on the lid of the project box, point the tab the opposite direction. Then when you insert the switch through the 1/4-in hole on the under side of the lid, the tab will slip into the 3/32-in hole, serving to prevent the switch from turning. See Photo 6b showing the switch mounted from below with the tab inserted in its hole. Now place the washer and nut on the switch on the upper side of the lid and tighen. The completed assembly is shown in Photo 6c.


LED holder

Photos 6c-f: The LED holder has two parts shown to the right. The first step in mounting the LED is to snap the collar of the LED holder into the hole from the upper side of the lid. See Photo 6c. From the under side of the lid, insert the LED into the collar as shown in Photo 6d. Note that one leg of the LED is longer than the other. Orient the LED so that the longer leg is toward the switch. Now you'll need to push the LED into the collar until the LED snaps into place. This may require quite a bit of force, depending on how tight the fit is. You can use a small, blunt instrument to push on the base of the LED until you hear it snap into place. The final part of the LED assembly is to place the ring over the collar on the under side and push it into place. Photo 6d show the ring in place. When the LED is correctly seated, it will appear from the upper side as shown in Photo 6e.


Photos 6f,g: The last part of the lid assembly is to add the standoffs. First, insert 4 of the 1/4-in bolts into the holes on the upper side of the lid as shown in Photo 6f. Then screw the 4 standoffs onto the bolts from the under side as shown in Photo 6g.

Photo 6a Photo 6b Photo 6c Photo 6d
Photo 6e Photo 6f Photo 6g  


Wiring the Project Box

Step 7. Adding the RCA jack and connecting the lid to the bottom of the project box


Photos 7a,b: The bottom of the project box has been predrilled as shown in Photo 7a. The large hole is for the piezo disc to pass through. The small hole on a long side is for the battery holder wires. The 1/4-in hole in a short side is for the RCA jack. Mount the jack now with the side tab on the inside of the box as shown in Photo 7b.


Photo 7c: Connect wires to the lugs of the RCA jack in preparation for connecting to the lid of the box and the PCB. Connect a 4-in green wire to the center lug and a 2-in white wire to the side lug. You can solder the connections now or wait to solder the remaining connections at the same time.


Photos 7d,e: In order to connect wires to the legs of the LED, first strip the wires back half an inch on one end. Do this for 2-in lengths of red and blue wire. Wrap the stripped ends around a brad or small nail as shown in Photo 7d. Then you can slip out the nail and slip the spiral wrap over the leg. Place the red wire on the longer leg of the LED and the blue wire on the shorter leg as shown in Photo 7e. When you solder these connections, solder near the base of the LED and snip off the protruding legs. This minimizes the chances that the legs will touch each other when assembling the box.


Photo 7f: Now it's time to connect the bottom of the box with the lid. Lay the two pieces out as shown in Photo 7f. Connect the white wire from the RCA jack to the center lug of the switch. Also connect the remaining 2-in length of white wire to the same, center lug of the switch. If you have connections left unsoldered, solder them now.

Photo7a Photo7b Photo 7c
Photo 7d Photo 7e Photo 7f


Wiring the PCB

Step 8. Wiring the PCB to the project box


Photo 8a: Next you'll connect the PCB to the components on the lid of the project box. Orient the PCB over the lid as shown in Photo 8a. Then solder the free end of the white wire from the switch to hole E on the PCB. You can solder on the under side of the PCB, the side on which the piezo disc is mounted.


Photo 8b: Solder the red wire from the LED to hole C on the PCB and the blue wire to hole A.


Photo 8c: Solder the green wire from the RCA jack to hole B on the PCB.

Photo 8a Photo 8b Photo 8c


Connecting the Battery Holder and Final Assembly

Step 9. Final assembly


Photo 9a: Prepare the battery holder by removing the plastic strip from of side of the hook and loop tape and sticking to the under side of the battery holder.


Photo 9b Thread the red and black wires from the battery holder through the 1/8-in hole in the long side of the bottom of the project box. Then remove the remaining plastic strip from the hook and loop tape and stick the battery holder to the side of the box.


Photo 9c: Solder the red wire from the battery holder to hole D on the PCB, and solder the black wire to the switch lug nearest the LED.


Photo 9d: Bolt the PCB onto the standoffs. Arrange wire positions as needed so that they won't be pinched when the lid is placed on the bottom of the box. Also make sure that the leads of the LED are far apart in order to avoid a short circuit.


Photo 9e: Fold the lid over onto the bottom of the box. The piezo disc should fit through the large hole in the bottom of the box. You can screw the lid in place now or wait until after testing of the unit.


Photo 9f: This shows the view from the opposite side of the project box.

Photo 9a Photo 9b Photo 9c
Photo 9d Photo 9e Photo 9f


This completes construction fo the Sount Trigger 2. Go on to Operation.



Assembly instructions for other kits




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