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Assembly and Operating Instructions for Kits


Assembly Instructions for the Sound Trigger on a Breadboard (SK2-BB)


Note: These instructions are for v10 kits.


Assembly instructions for other kits


While these instructions are for the SK2-BB, the photos all include a delay unit. If you are building the sound trigger with a delay (SK2-DU-BB), see these instructions for building the delay unit as well as the sound trigger.


A video tutorial is also available for this trigger kit.


Parts List


The following parts are included with the SK2-BB kit.


400-V SCR (EC103D)
2N2222 transistor (or PN2222A)
Piezoelectric disc


1 5.1-kΩ (green-brown-red)
1 100-kΩ (
1-kΩ potentiometer (yellow knob)*


*For kits purchased after 12-1-16, a red 2.5--kΩ potentiometer is substituted.

2 3" pieces of hookup wire
9-V battery cable (A 9-V battery is required but not included with the kit.)

Preparing the Microphone Cable


Note: In June of 2016, we started providing a new piezoelectric disc. Photos of the new and old discs are shown the right. The new version 2 requires the addition of a cable. For this purpose, the following additional parts are included in the kit: 1-ft of 2-conductor cable, 3-in of heat-shrink tubing, 2 breadboard pins.


Prepare the cable first according to these instructions.

Piezo disc piezo disc deep
Version 1 Version 2

For tools (not included), you'll need the following:

  • Wire stripper
  • 15-30 W soldering iron, solder, wet sponge
  • Lighter or matches to shrink the heat-shrink tubing


Click on the thumbnails below in order to view full-size images of the breadboard with the components that have been added in each step.


Using the Breadboard


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The breadboard offers an easy way to build electrical circuits without soldering. The 2"x3" breadboard provided with your kit contains an array of holes where wires and components are to be inserted. The holes in the center portion of the breadboard are identifiable by row (vertical in the photos) and column (horizontal).  There are two sets of 30 rows numbered by 5's, and each set of rows has 5 columns labeled A-E and F-J. The 5 holes on each row are electrically connected to each other (but not across the center channel), so any components inserted into the same row would be connected just as if they had been soldered.  However, the components can be removed and replaced with other components at any time, without the hassle of unsoldering and resoldering parts.


On either side of the breadboard are two columns marked by blue and red lines. The 25 holes in each column are electrically connected, but the columns aren't electrically connected to each other.  The outermost column marked with the red line at the top will be used for all +9 V connections, while the outermost column marked with the blue line at the bottom will used for all ground (negative) connections.


Assembling the Sound Trigger


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Step 1: Adding the Piezoelectric Element


The piezoelectric element is the sound detecting component of the circuit.  Place one of the microphone wires into 4A and the other wire into the (-) column. Polarity does not matter.

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Step 2: Adding the Wires


Now you'll add the hookup wires. You can estimate how much you'll need to bridge across two holes before cutting, although it's always better to have longer wires than ones that are too short.


Strip about 1/4" of insulation off each end. The list below will tell you which rows and columns your wire ends should fit into.


5-7J 3A to (-) 11A to (-)
5E-8F 7A to (-) 15A to (-)


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Step 3: Adding the Potentiometer


The 1-kΩ potentiometer (yellow)* allows you to adjust the sensitivity of your sound trigger.  It has three legs, two in the front and one in the rear. Place the two front legs over 7F and 9F, and the rear leg over 8J. The front legs should be facing the center of the breadboard, while the rear leg faces the outside of the breadboard. Press the legs in firmly as far as they will go, but avoid bending them.


*If your kit came with a red potentiometer, insert it in the same way as described above.

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Step 4: Adding the SCR and Transistor

SCR pin diagram


A = anode (+)
G = gate
K = cathode (-)

Transistor pin diagram

E = emitter (-)
B = base
C = collector (+)


The silicon-controlled rectifier (labeled EC-103D) is the output stage of the sound trigger. Putting in the SCR is easy since all three leads go in consecutive rows along Column B. To identify the leads of the SCR, hold it as in the diagram to the right. Put the cathode into 7B, the gate into 8B, and the anode into 9B.


The transistor looks identical to the SCR but is labeled PN2222A (or 2N2222A). Its three leads also go in consecutive rows along Column B.  To identify the leads of the transistor, hold it as in the diagram to the right.  Put the emitter into 3B, the gate into 4B, and the collector into 5B.



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Step 5: Adding the Resistors


Locate the brown-black-yellow resistor (100 kΩ).  Insert one end into 4D, and the other into 5F. Next, find the green-brown-red (5.1 kΩ) resistor.  Insert one end into 5I; the other end should reach over to the nearest hole in the (+) column.

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Step 6: Making Output Connections


Option 1: Connecting the Sound Trigger Directly to a Flash Unit


If you built a delay unit previously, then you've already prepared a trigger cable to connect the flash to the breadboard. If not, see the information in the yellow box.


A trigger cable is needed to connect your flash unit to the breadboard. The trigger cable kit is purchased separately, since there are different connectors depending on your flash unit. If you need a trigger cable kit, see this page.


Follow the instructions for assembling the flash trigger cable from your kit. (For quick reference, select a link: PC or FA kit / VPC kit.)


Once you've prepared the trigger cable, connect the wires to the breadboard according to this table.


Note that trigger circuits can also be connected to a camera shutter or wireless transmitter. See this page for more information.


Option 2: Connecting the Sound Trigger to the Delay Unit


If you would like to use the sound trigger with a delay unit, add a wire from 9E (sound trigger output) to 18F (delay unit input). Having constructed a delay unit, you'll already have an output cable for your flash prepared. You should connect your output cable to one of the following delay unit outputs instead of the sound trigger output.


For the delayed output (Output 2) of the delay circuit, connect the red wire to 17A and the black wire to the (-) column.


For the undelayed output (Output 1) of the delay circuit, connect the red wire to 13A and the black wire to the (-) column.


Important: If you connect your flash to the direct output of the sound trigger, be sure to disconnect the wire from 9E to 18F first. If this wire is left in place, some flash units can burn out the 556 timer.


Step 7: Testing and Operating Your Circuit


With a 9-V battery connected to the battery clip and your flash unit connected to an output, you can now test your circuit.  Clap your hands about three feet from the piezoelectric element.  The flash unit should discharge.  It may be delayed slightly if you're connecting to Output 2 of the delay unit. If you don't get a discharge, one possible reason is that the sensitivity isn't adjusted correctly.


Adjusting the sensitivity of the sound trigger: If you have a yellow potentiometer, turn it all the way clockwise for normal operation. If you have a red potentiometer, turn it to the halfway position.


Another way to adjust your trigger’s sensitivity is to vary the distance between the circuit and your sound source. The closer your circuit is to the source, the more intense the sound will be when it arrives at the piezoelectric element. Move the circuit closer for fainter sounds and farther away for louder sounds.






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