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Sound Trigger PCB

SK3 updated version is available here.

The SK3 Sound Trigger is completely redesigned from the SK2 model. The SK3 is our answer to customer requests for a more sensitive trigger in a project box enclosure. The SK3 responds to a wider variety of sounds than the SK2 and can be actuated by a finger snap at a distance of 30 feet or more.


While dynamic and condensor microphones can be used with the SK3, the best response is obtained with the included piezoelectric sensor (shown to the right).


The kit includes all the parts for the trigger control box and the microphone cable. Soldering is required for assembly. The circuit is assembled on the PC board shown to lower right. The board is bolted to the underside of the project box cover and is connected by jumper wires to the parts mounted on the cover. The photos below show two views of the interior.

Parts list

Assembly instructions


A cable is needed to connect the SK3 to your flash unit. You may already have a flash trigger cable from a previous kit that will work. If not, see the cable kits below.

Sound Trigger SK3

SK3 Sound Trigger Control Box

after assembly

Microphone cable
Microphone cable
after assembly
PCB assembled PCB SK3
Interior views of the box and PCB assembly

Here are other features of the SK3.

  • The trigger can be powered either with a 9-V battery or an optional 120-240 VAC to 9VDC adapter (neither are included).

  • There is an on-off switch and an LED to indicate that the trigger is on.

  • The 3-ft microphone cable is connected to the box through a 3.5mm mono jack.
  • The sensitivity is adjusted with a knob on the box.

  • There are two outputs. The switch output is used for flash units that are triggered by a simple circuit closure (such as units designed for synching with a camera), while the pulse output is used for flash units that are triggered with a low-voltage pulse (such as some studio units).
  • While delay is typically adjusted by changing the distance from the microphone to the source of the sound, another method is to connect the switch output to the input of a delay unit in order to adjust the delay electronically.

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