shootfirst
New Member
First some quick background.
For studio photography, it is typical to use several flash units to illuminate the subject. One of the ways to syncronize all of the flash units is by using an optical trigger also known as an optical slave trigger. The setup works like this - you have one flash that is triggered by the camera - all other flashes are attached to an optical slave trigger so that they will go off in unison with the master (camera triggered) flash. This optical slave trigger simply shorts two leads from the flash when the flash of the master light is detected.
Now the problem/question.
Most of these inexpensive slave triggers reportedly use an SCR (silicon controlled rectifier) that acts as the switch or trigger. Apparently from what I've learned, this SCR must have the current brought to zero in order for it to reset.
This is not a problem for most flash units on the market. But, the top of the line Canon Flash units will not function properly with a standard optical slave trigger. It will flash once, but after that it cannot reset. My guess is that there is some residual current flowing that does not allow the SCR to reset.
My question - is there a circuit I can place between the flash unit and the optical slave trigger that will bring the current to zero long enough so that the SCR can reset without interfering with the general operation of the slave trigger and flash?
The flash circuit is a relatively simple DC circuit - just 2 leads from the flash to the optical slave trigger. When these two leads are shorted together, the flash goes off. I'm not really sure exactly how either the flash or the optical trigger works, but the theory seems simple enough.
There was an individual that I found online that reported that he had placed an RC circuit in the system, but my attempts to duplicate his efforts have been inconsistent and I am unable to contact him.
Any help would be greatly appreciated!
Please let me know if you need any additional information. I have a multimeter and can take some measurements as necessary.
Thank you,
shootfirst
For studio photography, it is typical to use several flash units to illuminate the subject. One of the ways to syncronize all of the flash units is by using an optical trigger also known as an optical slave trigger. The setup works like this - you have one flash that is triggered by the camera - all other flashes are attached to an optical slave trigger so that they will go off in unison with the master (camera triggered) flash. This optical slave trigger simply shorts two leads from the flash when the flash of the master light is detected.
Now the problem/question.
Most of these inexpensive slave triggers reportedly use an SCR (silicon controlled rectifier) that acts as the switch or trigger. Apparently from what I've learned, this SCR must have the current brought to zero in order for it to reset.
This is not a problem for most flash units on the market. But, the top of the line Canon Flash units will not function properly with a standard optical slave trigger. It will flash once, but after that it cannot reset. My guess is that there is some residual current flowing that does not allow the SCR to reset.
My question - is there a circuit I can place between the flash unit and the optical slave trigger that will bring the current to zero long enough so that the SCR can reset without interfering with the general operation of the slave trigger and flash?
The flash circuit is a relatively simple DC circuit - just 2 leads from the flash to the optical slave trigger. When these two leads are shorted together, the flash goes off. I'm not really sure exactly how either the flash or the optical trigger works, but the theory seems simple enough.
There was an individual that I found online that reported that he had placed an RC circuit in the system, but my attempts to duplicate his efforts have been inconsistent and I am unable to contact him.
Any help would be greatly appreciated!
Please let me know if you need any additional information. I have a multimeter and can take some measurements as necessary.
Thank you,
shootfirst