1. Where can I get a piezoelectric microphone for a sound trigger?
2. Can I trigger my camera's electronic shutter with a photogate or other trigger?
3. Where can I get a sensitive sound trigger?
4. My flash doesn't have a PC cord.  How do I connect it to the trigger?
5. Can I use a visible light or other emitter for the photogate trigger?

1.  Where can I get a piezoelectric microphone for a sound trigger?

These are often carried by electronics wholesalers and catalog outlets.  Keep your eye on surplus outlets, too. If you have a Radio Shack nearby, the following part works fine for a sound trigger microphone:  piezoelectric buzzer element 273-073. You can also purchase one from the HiViz store.

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2.  Can I trigger my camera's electronic shutter with a photogate or other trigger?

This is a useful thing to be able to do if you're, say, photographing insects, birds, or other unpredictable subjects.  You simply can't hold the shutter open waiting for the subject to do its thing. Our triggers and delay unit will trigger either flash units or camera shutters that have electronic shutter cables. In order to do the latter, you'll need to cut your remote shutter cable in order to splice it to the trigger or delay unit output. The remote cables usually have 3 wires. Shorting 2 of them together performs the autofocus and exposure operations of the camera. Shorting the 3rd wire to the other two closes the shutter. You would use the output of the trigger or delay unit to perform the latter function.

Some cameras have shutter cables designed especially for DIY projects. An example is the Nikon MC-22 remote cord which works with the Nikon D series cameras with the exception of certain models (see below). The cable ends of the MC-22 are blue, black, and yellow. Shorting the blue and black ends together does the autofocusing and exposure operations. Shorting the yellow cable to the other two actuates the shutter.

Cameras with infrared remotes such as the D70/70s aren't well-adapted for use with our triggers. While you might be able to wire a trigger directly to the remote, the shutter lag may be unacceptable for high-speed applications. See this link for a discussion.

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3. 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 ~$17).  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.  The total cost including all parts (not the flash unit!) is ~$25.

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4.  My flash doesn't have a PC cord.  How do I connect it to the trigger?

If your flash unit doesn't have a cord, it must have connections on the foot for triggering it. You can get an adapter shoe that fits on the flash foot and has an output PC cord.  You should be able to find these in camera stores or purchase one from the HiViz store. More information on making connections is found here.

5.  Can I use a visible light or other emitter for the photogate trigger?

The photogate trigger circuit described on this site normally uses a small infrared emitter.  We've used it successfully, however, with the light from a flashlight.  It may also trigger on laser light. This requires precise alignment of the laser beam with the sensing element of the phototransistor.  For greater sensitivity, the infrared phototransistor can be replaced with a visible-light phototransistor such as the one shown on this page.

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