Problema con Flashes CANON 430EXII y
CANON 580EXII
Como ya sabeis, estos modelos de flash de canon no funcionan correctamente con photoduino. En la ultima revisión añadi un parametro para alargar el pulso que dispara los flashes, pero parece que no soluciona el problema, al menos en el 430EXII.
Recientemente un usuario de photoduino me consulto sobre como solventarlo y le comenté lo del parametro. Como no le funcionó estuvo investigando sobre el problema y encontró alguna información interesante sobre como solucionarlo.
Yo no tengo ninguno de los dos modelos, por lo que no puedo hacer pruebas, pero os pongo a continuación el texto de su mail (en ingles) para ver si podeis hacer alguna prueba. Parece que de las 3 soluciones que encontró, la mas sencilla de implementar con photoduino seria la 3, pues solamente hay que poner una resistencia de 10k y un condesador no-polarizado (ceramicos) de 10uF en paralelo con el flash y la conexión de photoduino para el mismo.
El resto de soluciones supone modificar el hardware actual, cosa que me parece dificil
Espero vuestras pruebas
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I've tried to change the value of DEVICES_FLASHES_SHOOTING_PULSE with bigger value but nothing has changed. The flash continue to lamp only once.
I've been gone a little in deep with this problem and I've found this is a common problem with all devices that use SCR to short flash contact. This affect not only canon flashes but also Yongnuo (chinese low cost flashes).
Below some snippet found googling:
* Most Canon EX-series Speedlites do not work well with most battery-free slave triggers from Fotodiox, Hama, Kaiser, Seagull and Wein. The flash will fire, but only once. The flash need to be power-cycled before it will fire again. The reason for is that the complex electronic circuits in these newer flashes prevents the Silicon Controlled Rectifer (SCR) used in these slave receivers from resetting. The Speedlite 580EX II, however, will work with such slave triggers if you connect it to the slave trigger through the built-in pc-sync port (it is just as uncooperative with these optical slaves as any EX-series flash if you connect through the hotshoe). When buying an optical slave to use with a Canon Speedlite, you should check that is compatible first.
* The problem is that old-style flash units use very high voltages for the trigger, and an SCR (thyristor) is by far the best way of triggering them. The problem with thyristors is that you can only turn them on - there's no way of turning them off other than stopping all current from flowing through them. Older flashes discharged the flash circuit completely, so this happened automatically each flash. Newer flashes don't work like this, which is why the trigger only seems to work the 1st time.
To solve this issue I've found a lot of theory...and I would like to hear also your thought.
Solution 1
The really easy way to fix this would be for Canon to design the flash differently - personally I think this is all part of the great Canon own-brand conspiracy. On a more practical level you can probably simply use a small 2n7000 instead of the thyristor as an earlier poster suggested. I designed my own flash-unit, and this is what I used. So I'm 99% sure it would work.What part-number is the thyristor? I can probably work out which way round to put the 2n7000 for you. Just don't connect your modified unit to an old-style flash, or it will break. A simple npn transistor (e.g. bc549) would also probably work as it would probably have a similar activation voltage and current to the thyristor.The thyristor issue is a common problem.
Solution 2
I simply replaced the SCR with a simple resistor (think it was 2N2222A) and it is now working perfectly. If you have a modern, low-voltage trigger you'll probably have to do the same.
Solution 3
Connect a 10k resistor and a 10uF nonpolarized capacitor in parallel. Connect this combination in series with one of your trigger wires. It shouldn't matter which one.
First two solutions (not checked yet) involves a change in photoduino board, last one just a resistor and capacitor on the flashes output.
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