First project: Laser tripped flash gun

I got my arduino yesterday having not messed with electronics since I was at school (over a decade). I decided to see if I could rig a flash gun so I could do some high speed photography.

I ended up with a laser (cheap laser pen) powered by the arduino and pointing at a photoresistor. When the light level drops it fires the flash via a relay. I added a couple of buttons (stop/go) and a couple of LEDs for good measure.

Rather pleasingly, it all worked. I need to improve the stage for taking photos, but all the kit works:
(I can’t post images or links as this is my first post, so you’ll have to copy/paste for a pic) cowjam.co.uk/arct/drop.jpg

More details including a rough circuit diagram (again not drawn one in over a decade, so sorry if it’s rubbish) and the code on my site: cowjam.net

I have no idea if the resistors are the right values. I based it on the ones used in the examples given in my starter pack.

CowJam

Here's the pic:

And the link: http://cowjam.net

Nice project. Be careful not get the breadboard electronics wet. How are you triggering the camera?

At the moment I'm using a pocket digital camera (an olympus mju 8000), which has a maximum shutter time of four seconds. I open the shutter then set everything going - the speed of the flash dictates the length of exposure.

I'm doing all this in the cupboard under the stairs as there are no windows. The process is - half press the camera button to get it to focus, keep my finger half pressed (or it'll change focus). Turn the light out. Press Go on the arduino. Fully press the camera button. Drop something.

With a bit of luck I'll drop whatever it is through the beam (not that easy in the dark). It's quite frustrating getting a good shot - my aim has to be right, I have a small window of time to get it done in and the autofocus has to be right and I have to have the camera aimed at the right section of the water.

I've changed the way the flash is fired now - once the the laser is shining it takes a light reading and fires the flash when the light level changes from that (with a sensitivity variable built in as I wasn't sure how sensitive it needed to be).

The next step is to put it in a box, rig the sensor and laser up so they're stable and build some kind of frame for dropping drops/marbles/whatever so they reliably go through the beam. Once I'm sure it's all sound and reliable I'll get my old SLR out, but I don't want to waste film getting crap shots like I am at the moment. I can manually focus the SLR, set the aperture and lock the shutter open, so it should be a little more relaxed then.

Sam

Hmm, maybe you could extend it a bit?

If you want to hack the camera too, then try and hook the shutter button up to the arduino too, along with the light in the room. Almost full automated then, and a buzzer to tell you when to make a drop. :slight_smile:

If your camera has an IR sensor or remote, you could trigger it that way by flashing an IR light at the same time as the flash. I'm sure you have already herd of Doc Edgerton, but if not, check him out too. http://en.wikipedia.org/wiki/Harold_Eugene_Edgerton

Thanks for the info.

The digital one might have IR, but from what I’ve read the response time is too slow for what I’m doing.

bld, I've contemplated using a servo for the physical remote trigger on the SLR (it's not digital, it's an Olympus OM2).

I might get another light - I don't really fancy dabbling with mains - it's a good idea though.

Okay, but if you change your mind

http://www.glacialwanderer.com/hobbyrobotics/?p=9 or http://www.emartee.com/product/41852/Arduino-5V-Relay-Module

It is pretty easy to do :)

Very tempting bld. Will those components work with 250v 50Hz? I'm British.

http://www.emartee.com/product/41852/Arduino-5V-Relay-Module

This relay output driver shield adopts Omron G5LA relay to supply 1 channel control, the max can link to equipment with 250V AC/DC, therefore it can be used to achieve so many effects,such as electric lamp control.

Yep ;)

Can't seem to that in a British shop. I'll have to call in to my local electronics store, I've little idea what I'm doing yet.

Awsome! I'm making photo gate measurement systems. I use a photo gate as a trigger for speed measurement but the principle is the same and the photo gate is supposed to be faster in response than the photo reisistor that comes with the starter kit. I think if you set up your laser trip wire at a fixed height from the water surface, say 50cm above water and out of the way of your camera's view, you can trigger the flash at 0.32 seconds after the trigger fires, which is the time it takes any object to fall 50cm from rest, then you can choose when exactly to snap the shot, the object just entering water or say 0.1 seconds after that. Might be good enough to get a few shots at different dropping of the object and stitch into a video.

luidr, having the laser/sensor just above the surface of the water (about 1cm) is plenty fast enough. I've had to add a small delay to get anything other than the object just touching the water :)

The video is a good idea.

I've improved the setup somewhat - mainly adding black material at the bottom and behind the stage, using a little 'helping hands' thing with a weighted base and clip on an arm to hold the laser in place.

Anyway, I just took this: Full size shot (5MB): http://cowjam.net/images/dolly_mix_full.jpg :D

Did you say you powered the laser diode directly from the arduino? I've been looking some info on this for ages, as I like you haven't played with electronics for a good while and would very much like to build a trippy laser light show too! :)

Yes, I did.

I used a cheap laser pen. It's not a particularly bright laser but it does the trick in a dark room.

Just an idea (I've read about it somewhere on the net a few months ago): you could also trigger the shot via a microphone capsule. When the object hits the water you have a sound, and the capsule emits a signal. If you capture it with an analog pin and are polling it fast enough you could catch the moment where the water jumps up after the object sinks.

I've read about that too, but haven't got round to it.

I've got a hall effect switch and some rare earth magnets pulled from old optical drives - I was going to try use that at some point. I reckon it's likely to be more reliable than the laser/light sensor and adding a delay so you capture the right moment isn't difficult.