A Simple Home Made Sound Trigger

in Tutorials
By stainedglass/Kevin (5,556) Send mail to this user on February 16, 2010 1:58:27 AM CST

A simple sound trigger that you can build yourself without spending $100's

My hobby is getting expensive, hahah - I am so 'in to it' that everytime I see a great picture on SIG or elseware I want to try it. Recently I read up on high speed photography, freezing very fast moving things and wanted to do it myself. One needs some kind of device to trigger a remote flash unit in a dark space to capture the moment. These timers and trigger's are commercially available but seemed too expensive for me, to justify playing around with the concept. So I decided to make my own.

The net has a huge amount of IP to do this, and this is where I got most of my ideas, this is what I did, and hope that it will add value to someone wanting to try it as well.

There are many DIY ways to do this, but I settled on purchasing an electronics kit for the primary component of the sound trigger and build it up from there. This is what I did;

1. I bought a Voice Activated (VOX) Remote Tape Recorder Switch kit, (uses Schmitt timer IC) called KIT13 costs about ~$10. I am in South Africa, got it from a electronics store called Communica. I am sure RadioShack must the same kit. This kit senses your voice (sound) and turns on a tape recorder via it's remote port, so it's a switch, and that's what you need to start. It uses a condenser microphone (electret type) which appealed to me as this is a very sensitive device.

2. Build the circuit, very easy just need small soldering iron and very thin solder. A multimeter is recommended in case you have problems getting it to work (which I did). One can get a cheap one of these for less that $10 as well. I got one and it works fine. It uses 6V power source.

3. The circuit closes a switch for the tape recorder remote plug. So instead of that I use the switch to turn on a IR LED when activated.

4. Ask for any 5mm 3.2V IR LED (emitting) and a 330 Ohm resistor. I use a 9V source for the IR LED, the resistor drops the voltage to around 3V. The correct resistor is important as a higher voltage will fry the LED. An example formula to calculate the resitor needed:

- Source V - LED Voltage = V

- V/LED Max A = R ohms

Such as:

- 9v-3.2v = 5.8

- 5.8/20mA = 5.8/.02A = 290 ohms (get the closest higher value resistor)

5. Connect the resistor in series to the LED and to the switch to close the circuit when the sound activates. I.e. Use the remote plug wires and the voice activated sound trigger as a simple switch to turn the IR LED on and off.

6. The IR LED fires my flash, a Nikon SB-800 in remote mode (off camera). From there the flash fires other flash units in commander mode, if multiple flash units are required.

7. You can use the switch to close a PC cord or a hot shoe if you flash does not have an IR port. Then you will need a Sensitive Gate SCR (Silicon-Controlled Rectifier) minimum 400V for a switch as some flash units emit a high voltage back on the line which will fry the sound trigger.

One can adjust the sensitivity of the electret mic, to extremely sensitive sounds and vibrations such as water drop sounds, all the way to over voice level sounds such as air rifle or ballon popping loud sounds.

One can read up on the 'net on how a sound trigger setup works, there is a lot of info on the subject. This one works just as well as any. The cool thing about this sound trigger is that after 6s of silence the device re-sets itself (IR LED go's off) and ready for the next shot

I am no electronics bof or photography bof but it is easy enough if you have the time to read up and do this. It took me two evenings to get it to work including the first photo.

This all costs a little time and less than $20!!

Please don't hesitate to contact me if you need help or more info...

Regards, Kevin Padoa - Stainedglass on PhotoSIG

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From cmsturgeon/Michael (2,934) Send mail to this user on July 25, 2010 10:10:41 PM CDT

Can you tell us of any photos that have come from your successfully building this ?


From stainedglass/Kevin (5,556) Send mail to this user on August 26, 2010 9:34:39 AM CDT

Hi Michael yes, have a look at my photo's under the portfolio 'high speed' was taken using the trigger.


From deleted22692269/deleted (2,209) Send mail to this user on December 29, 2011 8:43:00 AM CST



From mussa/Mussa (0) Send mail to this user on September 2, 2010 6:11:11 AM CDT

wow man..if its working than its a great discovery from you... please show us some of the photos that you have taken... i would like to see them.. keep up the good work


From gbomfim/Gilberto (36) Send mail to this user on February 16, 2011 9:32:53 PM CST

Very nice idea Kevin. I was try some devices without sucess, but it is good.


From diespook/Johan (716) Send mail to this user on August 14, 2011 10:36:18 AM CDT

I have been wanting to build myself a sound triger for a while now, thanks I will pop into comunica in the week and get me the kit, hope to show some pic's here soon where i used your idea.


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