camera controller?

Forum 2005-2010 (read only) Hardware Development
1

Hej,

I am a photography student and I'm looking for hardware to build a flash/camera controller.

I want to use my iphone and sensors(temperature, luminocity, sound, touch, humidity) as triggers.
In case of the iPhone I need a solution to use an electric sound signal through earphones as an input for the Arduino.
The other sensors, I believe, are easily build into the Arduino system, and I think I will find that info on this forum.

For the Output I need a secure system that fires the camera/flash.
These devices are triggered by remotes that simple just close the circuit.
So I need to keep the electricity from the Arduino seperated from the camera/flash (the higher voltage/amp would fry the Arduino)

These are alot of questions and I'am new to this. The software is no real issue since my brother is a C/C++ master. But I really need to know if I can build this thing with the Arduino hardware (I think so since I saw examples) but I just don't have a clue of what parts I need to buy.

Any help or comment is welcome.

Thx alot

2

Most people use something called a Silicon Controlled Rectifier or SCR to short two contacts on the flash hotshoe, which triggers it. This is not without dangers as wiring it up wrong can kill the Arduino pin the SCR is connected to. Example here.

It might be a good idea to add an opto-isolator between the SCR and the Arduino just to be safe, depending on budget and how important the chance of burning out a pin is.

Alternatively, you can get a pro strobe with a isolated 5V trigger input already built in if you have Lex Luthor's gadget budget.

::slight_smile:

3

That was really helpful, thx.
I was also thinking of a delay to program into the Arduino, but I would like to have a hardware controller for the amount of delay. Is there a part for these things?

This way you can drop a glass and trigger a flash in a dark room by the sound this causes, but with the delay you can choose the amount of breaking and shattering you want.

4

Yes, and another handy accessory is to be able to detect passage of the object at one point, than at another at a known distance, calculate speed and set off the flash so that the object is at a known position in the frame. Often used with bullets from air guns since their speed varies from shot to shot, not needed with falling object since they always fall the same way.

Some comments on timing delays on arduino:

  • there will be a fixed minimum delay for the sequence detect-event/set-off-flash which will have to do with the time it takes arduino to measure things and change values on pins. This will be small (a few microseconds) and more importantly, won't change much from shot to shot.
  • you can produce additional and controllable delays with good accuracy to the microsecond with arduino as long as this additional delay is more than 3 uS or so (just consider that 3uS part of your minimum delay, in other words)
  • you can produce ultra short delays (62.5 nS on a standard Arduino, this is processor clock dependent) by using a special operation which waste exactly one processor cycle.

If you need more accurate delay control than that, or a smaller minimum delay, than yes, you would need a hardware timer, which you could build yourself in a variety of ways (google timer circuits and prepare to be flooded) but keep in mind that unless you get a special flash you will have a hard time getting a flash duration under, say, 50 uS, so your Arduino will be plenty accurate enough!

50uS is 1/20,000 in photography parlance, just as a reference.

5

Yes these are exactly the things I'm looking for.
I want an all around flash/camera trigger that is capable of capturing any event autonomically.

Maybe you guy's should post any way to trigger a camera/flash here
as well as possible uses for this device.

At the moment I'm focussing on connecting the iPhone to the Arduino.
The iPhone could be used to trigger at certain time, time intervals, sequences or any combination of these things.

The iPhone also has a seismometer app and the mapping app, these could also be used as interesting inputs.
(sound travels faster as a vibration in solids than in gasses, so the seismometer could be better than a mic)

6

What opto-isolators or triacs you recommend?

In my application I think the biggest external power source I will use is 12v 500mA.

Would a 4N28 be enough?

An Arduino output pin would connect to 1, 2 on ground, should I put a resistor?
And on 3-4 is the 12v 500mA.

7

Check out this site Hobby Robotics » Triggering a Camera’s Flash with Sound and Light for some examples of using the Arduino to trigger a Cannon 30D and flash.

8

An Arduino output pin would connect to 1, 2 on ground

Yes, the Arduino would set the output pin to high, causing the LED to light up the phototransistor, causing current to flow thru the opto-isolator.

should I put a resistor?

Depends what the datasheet of the opto-isolator recommends as forward input current (the current thru the LED). If in doubt, treat it as any old LED and yes, put a resistor in series.

And on 3-4 is the 12v 500mA.

Not sure I understand what you mean by that, the idea is to use the opto-isolator to control the flow of current into the gate of the SCR while protecting the arduino side from any large voltages and/or current which occur on that side. The SCR should be set up to short two contacts on the hot-shoe when it goes conductive, and its gate or control input is the thing you want connected to the opto-isolator.

You could do what ericski's link (glacialwanderer.com) is suggesting here, and use the opto-isolator itself to short the flash contacts, but I believe that's a bit much for such a part and the SCR will serve you longer and better. Happily, the opto-isolator should fail without passing the damage on to Arduino in any case.

As for picking the opto-isolator, if you are using it with an SCR, it only needs to survive any nasty surprises coming out the SCR gate, so the SCR datasheet will tell you the minimum ratings you need. The one you pointed to should be fine, but do check with the SCR ratings.

If you are using the opto-isolator to short the flash hotshoe directly like glacialwanderer.com seems to be doing, you need something beefy that will stand a few hundred volts. Glacial wanderer's opto-isolator's datasheet seems to suggest the PS2532 is a rather macho part. The collector to emitter voltage is 300V and the isolation voltage is 5,000V, compared to 30V and 5,000V for the part you pointed to.

The collector and emitter are the bits which will connect the gate of the SCR to ground or the two flash contacts together (shudder) so for the latter, 300V is a good thing while for the former, 30V might be enough depending on the SCR. The isolation voltage is how much voltage can be applied to the flash side of the isolator without making it to the arduino side, so either part, at 5,000 volts, should be fine for protecting your I/O pins.

9

Hi Mathieu,

For triggering the flash, the 4N28 or the stronger PS2532 suggested by Glacial should be enough, modern flashes are not high-voltage on the hotshoe.

I'm actually thinking a similar use to activate a solenoid for the water dropper, and that needs 12v and 350mA, I think the SCRs on the optoisolators won't handle that much, I will look for a relay...

10

I have a healthy respect for the amount of joules a flash packs in its capacitors :wink:

Well, it won't hurt the flash or the arduino, and opto-isolators are not expensive parts, so heck, why not? Get a couple spares, if your supply chain is a bit on the long side, perhaps.