For a long time I had an old photo flash FIL 11M manufactured in USSR by local factory Norma.
There was a high-voltage synchrocontact on the flash, which suited ideally with a film cameras Zenit.
Now, film camera times have passed and they were exchanged by digital cameras. However photography principles are left the same and there is a still need in the light, including flash light. After playing enough with my Canon EX420 flash, I have decided to add a second flash into my lightning schemes. Buying original flashes is an expensive joy, buying chinese – is a lottery. So I thought I could use an existing old flash somehow.
After googling for a while, I have found out, that contemporary cameras have low-voltage contacts, and therefore some adapter is needed. However, wires is not the convenient way of connecting camera and the flash, and there are other means of synchronizing them using light, when the second flash is triggered by the light received from the first flash. As soon as the light reaches the synchronizer almost immediately, but working time and exposure time are long, comparing to this, we can say, that both flashes will trigger concurrently.
Further search got me to an excellent website osipoff.ru, where different photo flash related electronics is being discussed and where are the lots of synchronizer schematics.
I quickly found the simple schematic “Mercedes”, by Veryutin with lots of positive feedback. This schematic can withstand high voltages up to 300 V, which is according to FIL 11M specs. I tryed to made the schematic from the components I had and trying to make it as small as possible. So SMD parts were the primary choice. I had only 0805 sized resistors and they can hold only up to 150 volts, so I had to make a large 22 ohms resistance of several serially connected resistors.
Synchronizer started to work from the first time. Unfortunately it immediately came out, that this schematic is not suitable for synchronizing with contemporary consumer cameras, because they do flash two times. The first one is so-called pre-flash to check the exposure value and set the right values for the main flash and for the aperture. The second one is the main flash with correct parameters. With “Mercedes” synchronizer, the second flash was triggered during pre-flash and so the photo was underexposured as a result.
After some research, I have found couple of second-flash capable synchronizers. This time I did not take Veryutins’ schematics, because it has odd values on it and there were no few of the required parts left. But I have found another schematic, which was essentially the same and started to assemble it. It took twice the time to get the device assembled, but it did not worked right after that. I have checked it with the multimeter and found an unsoldered contact. After soldering it together, the schematic started to work properly.
Tried it in both modes. It synchronized perfectly after first and after second flashes.
Now it is time to make a photo set with the new lightning schemes.