Let's Make Robots!

Picture-Axe, Sound trigger to camera flash

Triggers a camera flash when a sound occurs. The divice is used for taking high speed images.

Photography is one of my many interests. I bought my first DSLR 12 months ago, and have experimented with it a lot.

I came across some nice high speed pictures and wondered how they managed to take them so I did a little research.

Because of the limitations of the moving parts in a DSLR high speed images are commonly taken with a long shutter speed in a dark environment with a fast flash.

First I tested this technique with a mechanical switch (microswitsh) mounted to a plate. I fired a soft air-gun trough a light bulb so that the bullet hit the switch (after passing trough the light bulb)  and fired the flash.

mechanical switch flash trigger















(soft airgun bullet fired trough a light bulb on to a micro switch witch triggers the flash. You can see the bullet when it bounces back from the switch befor the switch has ben fully triggerd)

I got a satisfying result, but I wanted to be able to trigger the flash on other events such as water balloons bursting, objects hitting the ground or colliding in air etc.

Sound seemed to be the logical choice, and google led me to some basic circuits for triggering flashes with sound, but I wanted to be able to control the delay and sensitivity and have different modes and functions. Thanks to LMR I new the solution. Microcontroller!

So I started boarding and building. Thanks to Frits "start here"-link and picaxe 28x1 wiki I was familiar with the 28x1 and happened to have a spare so I was off to breadboarding.

breadboarding SDC

I just copied the Sound detection circuit from picaxe's webpage and added some small modifications. (http://www.rev-ed.co.uk/docs/picaxe_sound.pdf)

Added a serial LCD. And started working with the code.


I hacked a cheap camera flash shoe so that it has a 3.5mm cable jack insted of a pc-sync cable. A 10 cm ling Pc sync cable is 10 times the price of a 150 cm 3,5mm cable.

There is a unused 3.5mm jack on the box for future comming functions. Might be a optical switch or a laser switch (gate) or then a camera shutter relese so that I for example could use this box for making timelapses. Currently Im using a graphical calculator for that.


inside pictureaxe

inside Picture-Axe

I have a Brain circuit, a Sound Detecting Circuit and a sensitive gate SCR to trigger the flash. The picaxe is not overclocked (running at 8MHz). The box has a 3.5mm jack for a picaxe USB download cable so it is easy to program more. The code is now about 400 rows (basic) with alot of white space. alot of code is taken up by the menu system. I will try to make some kind of strobe funktion to,






Hitting a cup as hard as I can (0 delay).


bouncing buttles

Another testshot


Me and my friend had a greate time playing with Picture-Axe



Smashing apples. (Eliminateing all signs of atumn)

bang bulb

End of lightbulb

pictureaxe red

My Picture Axe.

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

Dude, what's with all the astetics? Just hammer some apples and stuff, man! :D

Looks like I will be doing some tests whenever I have some time for it :)

Really cool pictures you took there! And this box looks neat as well. Do you have estimate of reaction time? Recently I've been thinking of similar project, but using uC and LDR to capture lightnings, but I'm not really sure it will be fast enough...

Geir, maybe you already have some info with ergards to this??

I don't dare to estimate how fast it can trigger the flash, or even where the bottleneck is but its pretty fast. If you want to make small delays you can always move the mic a couple of inches so it takes a longer time for the sound to travel to the mic.

Good work and really nice pictures.

Keep it up!


Great post and good build.

I built something similar only I used an Arduino as I had never heard of the PICAXE then. That was the first thing I ever built with a microcontroller. I used photo transistor and a laser pen as the trigger.
Sins then I have built different things related to photographic work, like this one http://letsmakerobots.com/node/16230 or this one http://letsmakerobots.com/node/16315

Great work Renkku!