Sound Activated Camera Flash

A quick and dirty and dangerous sound activated flash to catch moments in time

The First Thing You'll Need Is an Amplified Computer Speaker

The sacrificial victim here is a pair of harmon kardons from a garage sale $1

Crack the Case Open and Identify the Op Amp Used

then go to mouser and download the datasheet, in this case the chip is a ba4560. your looking for which pins are the amps +&- ins, there should be two pair. To determine which pair you need touch the leads (with power on) of a speaker to each pair of pins, one pair should give a much louder feedback than the other. Note those two pins.

In This Step We'll

disconnect the leads from the speaker, cut the traces to the RCA jack that the slave speaker connected to, and attach hookup wires to the op amp pins we identified.

Next Take the Hook Up Wires You Connected to the Op Amp and Attach Them to the Speaker.

They are attached in series with a 1 k pot and a 3.6 micro farad capacitor, the pot acts as a sensitivity control.

Now You'll Need an SCR

I used a 2n687, I tried a couple of diff ones before I found one that works, I hope you have a good junk store near by, mine came from Skycraft in Orlando. Anyways to hook up the SCR attach the the positive lead that originally went to the speaker to the SCR's gate. The negative lead to the speaker is attached to the SCR's Cathode. At this point a multimeter in diode mode across the SCR can be used to verify operation. So power up and test you'll get a variable reading across the SCR when you tap the speaker if it's working

Connect the SCR to the RCA Connector

This is easy, just jumper the anode and cathode of the SCR to the RCA connector

Now to the Camera

Cut the cord off the slave speaker and set it aside, get a disposable camera from a drug store or someplace. BTW CVS hooked me up, Walgreens gave me the Bum's Rush. Crack open the camera, remove the battery and short the big capacitor, getting zapped hurts, so be careful. examine the mechanism to identify the flash trigger switch and attach the end of the cable you set aside to either side of the switch.

At This Point Your Almost Done.

seal up the camera (put the battery back in), plug the cord from the camera into the modified amp, hook up power and tap the speaker, if it doesn't flash reverse the leads and try again, if it still doesn't work, I dunno? it worked for me. One thing about the power, use a battery, I used a nine volt, the 60hz hum from the transformer messed it up.

here's some pix These were taken with a Canonette film camera with ISO 400 film, you need absolute darkness, so set up, flip the lights off, open up the shutter, drop something, close shutter and turn the lights back on to reset. Sorry about the pictures I realise this is not the clearest of instructables, but i think with some though you can follow it. Remember EMP kills.