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Assembly and Operating Instructions for Kits


Instructions for Building the Sound Trigger 4 (ST4)


Assembly instructions for other kits


Photo Gate 28




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 these instructions, 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.

  7. A drill motor and these drill bit sizes: 3/32, 1/8, 1/4, 5/16 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. Small, round file
  11. Stencil or razor knife and a straightedge
  12. Hole punch such as that used for punching paper for binders
  13. 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.


Adding Components to the PCB

Step 1. Adding the IC sockets to the PCB


Photo 1a: This photo shows the upper side of the PCB for the project.


Photos 1b,c: Three 8-pin sockets will be soldered to the board. Note in Photo 1b how the notch in the end of a socket corresponds to the notch in the corresponding figure on the PCB. Seat all of the sockets in their respective locations on the board as shown in Photo 1c.


Photo 1d: The photo shows the underside of the PCB. Crimp the pins of the sockets over in order to hold the sockets in place and prepare for soldering.


Photo 1e: Solder the pins, being careful not to bridge solder between pins. If this happens run the tip of the soldering iron between the pins to remove the bridge. This may take several tries.


Photo 1a Photo 1b Photo 1c
Photo 1d Photo 1e  


Step 2. Adding the resistors to the PCB


Photos 2a,b: Cut a 1-in length of yellow wire. Strip 1/4 inch from each end. Bend over the stripped ends as shown in Photo 2a. Insert the ends of the wire into the location labeled R5 on the board as shown in Photo 2b. Then solder the legs on the back side of the board.


1k-ohm resistorPhoto 2c: Start with the 100k resistor (see photo to the right). The resistance value is indicated by the sequence of band color, brown-black-yellow in this case. 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. In a similar way, insert one of the 1k resistors into location R2. Then solder the legs of the resistors to the back side of the PCB.


Photo 2d: Clip off the excess leg lengths for the yellow wire and the two resistors. The completed solder connections, surrounded in yellow circles, are shown in Photo 2d.


Photo 2e: There are 8 remaining resistors. (Two of these will be soldered on the lid in a later step.) Solder the following six resistors to the board as given below. No resistor will be soldered in location R9.:

  • R3 = 1M (brown-black-green)
  • R4 = 22k (red-red-orange)
  • R6 = 1k (brown-black-red) yellow-violet-brown
  • R7,R8 = 680 (blue-gray-brown)
  • R10 = 10 (brown-black-black)

Photo 2a Photo 2b Photo 2c
Photo 2d Photo 2e  


Step 3. Adding the capacitors to the PCB


Photos 3a,b: There are two kinds of capacitors, ceramic and electrolytic. The ceramic capacitors have a disc shape, are orange or tan in color, and are non-polar. The latter means that it doesn't matter whether the legs are switched when inserted into the holes on the PCB. A number on the disc identifies the capacitor. The capacitor in Photo 3a, for example, has the number 473. From the Parts Guide, you can determine that this is a 0.047-μf capacitor. The electrolytic capacitors have cylindrical, blue cases, and they are polar. So you have to be careful of the orientation in which they're inserted into the PCB. The negative leg of an electrolytic capacitor is the shorter one. The value of the capacitance is written on the side. Photo 3b, for example, shows a 10-μf capacitor.


Photos 3c: Photo 3c shows the 2.2-μf capacitor in the location C1 on the PCB where the capacitor will be soldered. The "+" sign printed on the board indicates where the longer, positive leg is inserted. Insert the legs of the capacitor into the holes but leave about 1/8" of the legs protruding as shown in Figure 14. Bend the legs over on the back. Then solder the legs on the back and snip them.


Photo 3d: Photo 3d shows a 0.0047-μf capacitor (472) inserted in the location C6. Solder and clip the legs as you did for the previous capacitor.


Photo 3e: There are 7 remaining capacitors. Solder these capacitors to the board as given below. The board with all capacitors soldered is shown in Photo 3e.

  • C2: 10 μf (electrolytic)
  • C3: 0.1 uf (104; ceramic)
  • C4: 470 μf (electrolytic)
  • C5, C7: 0.047 μf (473; ceramic)
  • C8: 4.7 μf (electrolytic)
  • C9: 100 μf (electrolytic)

0.0047-uf capacitor

10-uf capacitor

Photo 3a Photo 3b Photo 3c
Photo 3d Photo 3e  


Step 4. Adding the SCRs to the PCB


Photo 4a: Insert the SCR (labeled EC103D) into the location labeled D2 on the PCB. Align the flat side of the SCR with the corresponding shape on the board. Push the component down to seat the legs firmly. Solder the legs on the underside of the PCB. Avoid overheating the SCR as damage could be caused to the component. If you take too long soldering on a particular leg, wait for the SCR to cool before moving onto to another leg. Be careful to avoid bridging the solder between legs. Clip the protruding legs when finished.


Photo 4b: Slip the SCR (labeled TYN408G) into the location D2 on the PCB. Note the orientation of the SCR in Photo 4b. Seat the legs as far down as possible and solder. This SCR has a backing which serves as a heat sink; nevertheless, avoid heating to component too much as you solder. Clip the protruding legs when finished.


Photo 4c: This photo shows a view of the board with all components in place with the exception of the ICs, which will be added later.

Photo 4a Photo 4b Photo 4c


Preparing the Project Box

Step 5. Drilling the lid and the bottom of the box


Note that Photos 5a-c show the veiw from the underside of the project box lid.


Photo 5a: Cut out the drilling template and place it in the underside 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 holes on the template.


Photo 5b: Remove the template. Drill 3/32-in starter holes at each of the locations that you marked.


Photo 5c: Drill the starter holes to the sizes indicated on the template. Note that the hole for the Test button is slightly larger than 1/4 inch. If you have a 9/32-in bit, use that. Otherwise, use a small, round file to enlarge the hole so that the pushbutton will fit.

Photo 5a Photo 5b Photo 5c


Step 6. Adding the label


Photo 6a: 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 6b: 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 6c: 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. Use a stencil or razor knife or sharp scissors to trim the excess laminate from around the label.


Photos 6d,e: Use a 1/4-in hole punch to punch out the 1/4-in and 5/16-in holes on the label as shown in Photo 6d. If you don't have a hole punch, the point of a sharp knife can be used to carve out the holes. Don't worry if some edges are ragged. These will be covered by the components later. The label with holes punched is shown in Photo 6e. The 1/8-in holes will be punched later.


Photos 6f-h: Now it's time to glue the label to the top of the lid. For glue, use rubber cement or other repositionable adhesive. First cut the 2-in section of plastic tubing into two 1-in pieces.Then spread the adhesive over both the lid (Photo 6f) and the underside of the label (not shown). Place the label in position on the lid, and align it using the two pieces of plastic tubing. Push one piece of tubing through the On-Off hole and the other through the Flash hole as shown in Photo 6g. 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. When completed, the lid with label should look like Photo 6h.


Photo 6i: Use a knife to expand the punched holes for the Sensitivity pots to 5/16 in. Then check the underside of the lid to see if portions of the label overlap any of the 1/4-in holes. In particular, the Test hole may need to be enlarged. Uuse a stencil knife, razor, or knife blade to trim the label back to the boundaries of the holes. This will make it easier to insert components later.


Photo 6j: Use a small screwdriver or pencil point to push through the 1/8-in holes. It's not necessary to clean the paper out of the holes. This will be covered by the bolts later.

Photo 6a Photo 6b Photo 6c Photo 6d
Photo 6e Photo 6f Photo 6g Photo 6h
Photo 6i Photo 6j    


Adding Components to the Lid of the Project Box

Step 7. Adding the jacks and LEDs


Photos 7a,b. Photo 7a shows the underside of the box lid. Mount the pushbutton and the two RCA jacks in the locations shown. Note the orientation of the tabs of the jacks.While this orientation isn't essential, it will help in wiring later Photo 7b shows the upper side of the lid with the three parts added.


Photos 7c,d: Mount the two 3.5mm mono jacks (cream colored) and the 3.5mm stereo jack (black) in the locations shown in Photo 7c. Orient the tabs as indicated. Next, push four of the steel bolts through the 1/8-in holes on the upper side of the lid. Then screw the four standoffs to the protruding bolts. Photo 7d shows the upper side of the lid with the components mounted so far.


LED holder

Photos7e-g: The LED holder has two parts shown to the right. The first step in mounting an LED is to snap the collar of the LED holder into the hole from the upper side of the lid. Do this for the Power and Trigger LEDs. Then, from the underside of the lid, insert the Power LED into its collar as shown in Photo 7e. Note that one leg of the LED is longer than the other. Orient the LED so that the longer leg is the one nearer the outside of the lid. 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. Next insert the Trigger LED into its collar but, this time, orient the LED the opposite way. See Photo 7f. Screw the rings onto the collars to complete the assembly. Photo 7g shows the mounted LEDs from the upper side of the lid.

Photo 7a Photo 7b Photo 7c Photo 7d
Photo 7e Photo 7f Photo 7g  

Step 8. Adding the switches and variable resistor


Photos 8a-c: The switches will be mounted next. In Photo 8a showing a 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 underside of the lid, the tab will slip into the 3/32-in hole, serving to prevent the switch from turning. Photo 8b shows the underside of the lid with the two switches mounted.The upper side of the lid with both switches mounted is shown in Photo 8c.


Photos 8d-g: The final component to mount is the variable resistor, also known as a potentiometer or pot. Note that there are 2 washers under the nut. Remove the nut and one of the washers. Note also that there's a metal tab beside the shaft. We recommend snipping off about one-third of the tab so that it doesn't create an indentation in the lid label when mounted. See Photo 8d. Slip the pot through the underside of the lid as shown in Photo 8e. On the upper side of the lid, place the remaining washer and the nut on the shaft and tighten. See Photo 8f. Before adding the knob, turn the shaft of the pot all the way counterclockwise. This is the 0 position. Loosen the set screw on the knob and mount on the shaft with the white indicator mark pointing to zero. Tighten in place. Photo 8g shows the lid with the knob mounted.

Trimming the height of a tab
Photo 8a Photo 8b Photo 8c Photo 8d
Photo 8e Photo 8f Photo 8g  


Wiring the Project Box Lid

Step 9. Wiring resistors and wires to the lid


Refer to this graphic to identify pins and part IDs in wiring the lid. Note that the black wires shown in the graphic are white wires in actual use.


Don't solder any connections until instructed to do so.


Photo 9a: You ahoul have two 1k resistors left. These are wired on the lid.In order to prepare the resistors for wiring, wrap one end of each resistor around a small nail or brad as shown in Photo 9a. Slip this spiral for one of the resistors down over the shorter leg of the Power LED (LED1) as shown in Photo 9a. Then connect the other end of the resistor to lug 1 of the Mic In (J1) jack. For the other resistor, slip the spiral end over the shorter leg of the Trigger LED (LED2). Connect the other end of this resistor to lug 1 of the Sensitivity pot (P1).


Photo 9b: The white wires will be connected next. Cut and strip the needed lengths (1/4 inch on each end) to make the following connections.

  • Lug 3 of the Power switch, SW1, to lug 1 of the Sensitivity pot, P1
  • Lug 1 of P1 to the side tab of the Pulse Out jack, J4
  • The side tab of J4 to the side tab of the Flash jack, J2
  • The side tab of J2 to either lug of the Test pushbutton, SW3
  • The side tab of J2 to lug 1 of the Aux In jack, J5
  • Lug 1 of J5 to lug 1 of the Mic In jack, J1

Photo 9c: Cut and strip a blue wire to make the following connection: Lug 3 of J5 to the free lug of SW3. Then cut a 2-in length of green wire. Strip one end back by 1/4 inch and the other by 1/2 inch. Spiral the latter end around a nail as you did for the resistors. Slip this spiral end down over the longer leg of LED2. Then connect the other end to the center lug of J4.


Photo 9d: You may now solder some of the connections. Solder the connections circled in yellow in Photo 9d. Next, you'll add jumper wires to the unsoldered connections.


Photo 9e: Here you'll add wires that will connect to the lid on one end and to the PCB on the other. When you strip the wires, strip one end back by 1/4 inch (for connection to the lid components) and the other end back by 1/8 inch (for connection to the PCB). You may solder these wires to the lid components as you add them or wait until you've added all of them. The chart below indicates the color, length, and connection point on the lid of each wire. Photo 9e shows all wires connected but unsoldered, while Photo 9f shows all wires soldered.


Color Length Connection point on lid   Color Length Connection point on lid
blue 2 Lug 3 of switch, SW2 green 2 Lug 2 of SW2
yellow 1.5 Lug 1 of SW2 green 1 Center lug of Pulse Out jack, J4
green 1 Lug 3 of Mic In jack, J1 yellow 1 Lug 3 of Shutter jack, J3
blue 2.5 Lug 3 of Sensitivity pot, P1 blue 1 Lug 2 of J3
white 1 Lug 1 of J1 green 1.5 Lug 1 of J3
yellow 2 Lug 2 of P1 blue 1.5 Lug 3 of Aux In jack, J5
yellow 2 Center lug of Flash jack, J2      
Photo 9a Photo 9b Photo 9c Photo 9d
Photo 9e Photo 9f    


Connecting the Wires to the PCB

Step 10. Connecting the wires to the PCB


Continue to refer to this graphic to identify pins and part IDs.


Photo 10a: In preparation for connecting wires to the PCB, place the PCB on the standoffs as shown in Photo 10a. Don't bolt the PCB down yet. Now make the following connections. Insert wires from the underside of the PCB and solder them to the upper side as you go.


Color Connection point on lid Hole on PCB
blue Lug 3 of switch, SW2 A
yellow Lug 3 of Shutter jack, J3 K
blue Lug 2 of J3 L
green Lug 1 of J3 M
blue Lug 3 of Aux In jack, J5 O


Photos 10b,c: Photo 10b shows a side view of the connections to holes A and O, and Photo 10c, shows a side view of connections to holes K, L, and M.


Photo 10d: Now connect wires to these holes. Note that this is no connection to hole N. Also, the connection to hole G will be made later.


Color Connection point on lid Hole on PCB   Color Connection point on lid Hole on PCB
yellow Lug 1 of SW2 B yellow Lug 2 of P1 F
green Lug 3 of Mic In jack, J1 C yellow Center lug of Flash jack, J2 H
blue Lug 3 of Sensitivity pot, P1 D green Lug 2 of SW2 I
white Lug 1 of J1 E green Center lug of Pulse Out jack, J4 J


Photo 10e: Cut a 2.5-in length of red wire. Strip this back by 1/8 inch on one end and 1/2 inch on the other. Spiral the longer end around a nail. Solder the shorter end to hole G on the PCB. Drop the spiral end over the longer leg of the Power LED, LED1. You may solder the connection, but don't clip the leg yet, as there will be one more wire to add in the next section.

Photo 10a Photo 10b Photo 10c Photo 10d
Photo 10e      


Wiring the Battery Holder and Completing the Box Assembly

Step 11. Wiring the battery holder and completing the assembly


Photos 11a,b: Cut 1-in sections of black and red wire. Strip each wire back half an inch on one end. Also strip the red and black wires of the battery holder by the same amount. See Photo 11a. Twist the black battery holder wire around the short, black section. Do likewise for the red wires as shown in Photo 11b. Then solder the connections.


Photo 11c: Cut two 1-in sections of the 3/32-in heat shrink tubing and slip over the soldered connections. Use a lighter or match to shrink the tubing. Note that the purpose of these extensions is to make the wire ends less likely to break when the lid is removed for battery replacement.


Photo 11d: Connect the black wire of the battery holder to lug 2 of the Power switch, SW1. Form the stripped end of the red wire into a spiral and connect it to the longer leg of the Power LED, LED1. This completes the wired connections.


Photo 11e: In order to avoid having the wires connected to holes B and M of the PCB coming into contact with the nearby standoffs, you can wrap some electrical tape around those standoffs.


Photo 11f: Bolt the PCB to the standoffs. Use the 2 plastic bolts for the right side of the PCB. Again, this is for electrical insulation from the nearby wired connections. Next, insert the two PS2501 chips into the lower of the 8-pin sockets. The white dots on the PS2501 chips are located to upper left as shown in Photo 11f. Once the pins are aligned, push down, applying as nearly equal pressure as possible on the surface of the IC to seat all pins. Repeat with the 555 timer in the upper left socket and with the LM386 chip in the upper right socket. Note that the notch in one end of the socket aligns with the notch on the chip.


Photo 11g: Position the battery holder in the bottom of the project box as shown in the photo. Use the supplied hook-and-loop tape to affix the battery holder securely to the bottom of the box.If the power switch of the box is on, turn it off. Then insert a fresh battery into the battery holder.


Photo 11h: Place the lid on the box, being sure to seat it completely without any wires being pinched. Then the screw down the 4 corners of the box, or, if you wish, leave the screws off until after you've tested the box.

Photo 11a Photo 11b Photo 11c Photo 11d
Photo 11e Photo 11f Photo 11g Photo 11h


Wiring the Microphone Cable

Step 12. Wiring the microphone end of the cable


Photo 12a: You'll first prepare one end of the gray, 2-conductor cable with connections for the microphone. Strip back the gray insulation by 2 inches on one end only. Then strip the red and black conductors by 1 inch each. Cut two pieces of 3/32-in heat-shrink tubing and slip over the red and black conductors.


Photo 12b: Strip each of the pin receptacles back by 1 inch on the wire ends. (Note that the colors of the wires may be different than red and black in your kit.)


Photos 12c,d: Twist the bare wires of the 2-conductor cable and the pin receptacles together as shown in Photo 12c. Then solder the connections (Photo 12d).


Photo 12e: Slip the heat-shrink tubing over the twisted wire connections. Then shrink the tubing with a heat source such as a lighter or match.


Photo 12f: Slip the 3/16-in heat-shrink tubing over spliced connections as shown in Photo 12f. Then shrink the tubing.


Now you'll move to the other end of the 2-conductor cable to connect the 3.5mm mono plug.

Photo 12a Photo 12b Photo 12c Photo 12d
Photo 12e Photo 12f    

Step 13. Wiring the 3.5mm plug


See the instructions below for connecting the 3.5mm mono plug to the other end of the gray 2-conductor cable.


3.5mm mono plug

Photo 1


See Photo 1 for the 3.5mm mono plug that you'll connect to one end of your cable.

Photo 2

Remove the jacket from the plug and slip it over the cut end of the cable. The threaded end must be toward the cut end of the cable. Strip back the gray insulation on the free end of the cable about 1/4" and then strip the insulation on the red and black wires about 1/8". See Photo 2.

Photo 3

Insert the stripped wires into the holes on the terminals of the 3.5mm mono connector. The red wire goes in the shorter terminal as shown in Photo 3. Don't crimp the metal tabs around the cable yet, as this will cause the insulation to melt when you solder.


Photo 4

Solder the connections. Since there's so much metal, it will take some time for the soldering iron to heat the metal. Tin the tip of the soldering iron with solder first. Then hold the tip of the iron flat on the metal to heat it up in the vicinity of where you want to solder. Touch the solder to metal and wait for it to start flowing. This is the way to ensure a good electrical connection rather than a cold solder joint. The completed solder job is shown in Photo 4.

Photo 5

Clip off any stray wires and then crimp the metal tabs around the gray cable as shown in Photo 5.

Photo 6

The completed connector is shown in Photo 6.

Step 14. Completing the cable


Photo 14a: On the microphone end of the cable, connect the red pin receptacle to the pin labeled M on the piezo disc. Connect the black pin receptale to the pin labeled G. There is no connection to pin F.


Photo 14b: The completed microphone cable is shown.

Photo 14a Photo 14b    


This completes the assembly of the Sound Trigger 4. Go to Operation of the Sound Trigger 4.




Assembly instructions for other kits




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