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Frequently Asked Questions

 

Questions about Sound Triggers

  1. Where can I get a sensitive sound trigger?

  2. Can I replace the piezoelectric microphone in the SK2 with an electret or other microphone?

  3. Is the SK2 sound trigger sensitive enough to capture a water splash with the sound of the splash?

  4. How can I keep the sound trigger from going off two or more times in rapid succession?

  5. I'm using the SK2 sound trigger to actuate my camera shutter when the space shuttle launches. However, the trigger is too sensitive for this application. What can I do to reduce the sensitivity?

1. Where can I get a sensitive sound trigger?

 

If you want to make your own, details are given here, or try the following. (This idea comes from Brian Kelly, a mechanical engineer from Flint, Michigan.)

 

Use Radio Shack's Audio Amplifier-Speaker (part no. 277-1008, price ~$14.99 online). Connect a microphone to the amplifier input with a 1/8" 2-conductor phone plug. Connect a 400-V SCR to the external speaker output, also a 1/8" phone plug port. (Click on the link above for the method of connecting the SCR to the speaker output and also to your flash unit.) This sound trigger works great. With the volume turned high, it responds to a whisper up to a foot away and to a normal speaking voice at 3 feet. We were able to get the unit to trigger on a finger snap between two widely-separated rooms in a house. With the volume turned very low, the trigger doesn't respond to the spoken voice (useful when you don't need the sensitivity and don't want the flash going off whenever you speak), but it does trigger on finger snaps up to 6 feet away. The results probably depend on the battery and the microphone. We were using a fresh 9-V battery (a 9-V DC adapter can also be used) and an electret condensor microphone. 

 

2. Can I replace the piezoelectric microphone in the SK2 with an electret or other microphone?

No. The sound trigger isn't designed to be used with such microphones. If you need a sound trigger with a wider frequency response and greater sensitivity, see the previous item. Also, the sound trigger built into the Multi-Trigger 2 provides a wide frequency response.

 

3. Is the SK2 sound trigger sensitive enough to capture a water splash with the sound of the splash?

 

The SK2 is designed to trigger on loud and sharp sounds such as that of a balloon burst, hand clap, or finger snap. In order to capture water splashes, a photogate with delay is the recommended trigger. The drop passes though the photogate and starts the delay timer. After a preset delay, the delay unit triggers the flash unit or camera.

 

4. How can I keep the sound trigger from going off two or more times in rapid succession?

A method that works with some flash units (the Vivitar 283 is one) is to put a 100 microfarad capacitor across the output wires to the flash. If the capacitor is polarized, experiment with the polarity. If neither orientation works, then this method won't work with your flash unit.

 

I'm using the SK2 sound trigger to actuate my camera shutter when the space shuttle launches. However, the trigger is too sensitive for this application. What can I do to reduce the sensitivity?

There are a couple of things you can try. Replace the 100k fixed-value resistor with a smaller one, say 68k. Or replace the 1k pot with a larger one, say 2.5k or 5k. Turn the resistance up to decrease sensitivity.

 

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