Flash trigger for new and old flash units

Hello,

I know that the Arduino and flash trigger subject has been discussed many times but I could not find a solution to my problem.

I tried building http://www.glacialwanderer.com/hobbyrobotics/?p=10

Like many people that wrote in the comments section I could not get it to fire my flash. The circuit works because it can trigger my camera. So the problem is that my flash unit is not compatible with that electronics setup.

The next step would have been to try with a SCR but in the same comments someone mentioned that SCRs won't work with newer flash units. Me and my friends have many flash units both old and new and we would like a setup that can trigger all of them or most of them.

The only thing that I found that works are relays but those have big delays and can't really be used for high speed photography.

So, does anyone know of a flash trigger setup that works with Arduino and can trigger both new and old flashes?

Ideally I would like something that can trigger up to 400V but I would be very happy with 250V.

Thanks!

...I could not get it to fire my flash. The circuit works because it can trigger my camera. So the problem is that my flash unit is not compatible with that electronics setup.

Do you have a voltmeter or any way of checking the voltage across the trigger contacts, that is... check the voltage out of the trigger input with nothing connected. Maybe the polarity of the strobe and camera are opposite? Try reversing the output connections to the camera/strobe.

If reversing the connections works, a DPDT switch can be added to reverse the polarity as needed.

The REAL problem is, for any given strobe we have no idea what kind of voltage and current are being switched by the strobe contacts... All we know is that when you close a switch, the strobe fires.

The only thing that I found that works are relays but those have big delays and can't really be used for high speed photography.

You can try a solid state relay. A solid state relay is basically a high-powered opto-isolator and there are reasons why it will not perform like a mechanical relay...

  • DC solid state relays only work in one direction, like the opto-isolator. If you have a "polarity problem" that results in some flashes devices working and others not working, you will have the same issue with a DC solid state ralay.

  • AC solid state relays work in both directions, but they often use TRIACS which are similar to SCRs. An SCR/TRIAC will turn-on when triggered, but won't turn-off until the current reaches (near) zero. This is usually not a problem with AC, since the voltage & current pass-thru zero twice per cycle. But, if the strobe trigger circuit keeps current flowing as long as the switch is closed, the strobe will fire once and won't reset.

The only thing that I found that works are relays but those have big delays and can't really be used for high speed photography.

In your application, is there a possibility of delaying the camera several milliseconds to match the strobe? Or, is there a way to "look ahead" and trigger the relay in advance of the camera?

relays ... have big delays

Are you sure? What sort of delays do you need? I see some reed relay specs that say 0.5ms. That's long on the electronic scale, but pretty small for (say) flying insects...

Ideally I would like something that can trigger up to 400V but I would be very happy with 250V.

MOC3020

Take a look at the highviz flash triggers and their Faq http://hiviz.com/Faq’s/flash_trigger.htm#9

They have spent a lot of time testing basic flash triggering circuits with a wide variety of flashes.

westfw:

relays ... have big delays

Are you sure? What sort of delays do you need? I see some reed relay specs that say 0.5ms. That's long on the electronic scale, but pretty small for (say) flying insects...

For high speed photography delays of the order of a few microseconds are desired-even shorter if possible. It is also vital that the delay be very consistent-something I wouldn't expect from a physical relay.