Referencing Post #34 from FvM,
1) “Post #16”: You are absolutely correct. I took the last 2 images after removing the test bulb, but before moving the return (Black) wire to where it links to negative & completes the circuit. Sorry, but I do have this in place during testing with the flash unit.
2) “if there’s some circuit feature inside the flash unit maintaining current flow after the flash bulb is burned”: Absolutely! The circuit inside the Graflite flash unit is closed by two means. Number 1 is the positive & negative leads of the cord connecting from the flash unit into the breadboard as indicated in the images. Number 2, is a flash bulb being inserted into the flash unit.
This is why the setup functions correctly for the first “flash”, but not subsequently. The spent bulb still keeps the circuit closed at that point, which keeps the current flowing on the breadboard & through the SCR.
When the spent bulb is removed & replaced, the second the new bulb touches the contacts in the flash, it ignites the new bulb.
3) “hasn't been already solved by other photographs with better electronic skills?” I whole heartedly agree that I do not have much experience. In fact I have been trying to learn everything I can to solve the problem. There is a catch.
Ok, this is where the conversation always goes when I am discussing this with people. As best as I have been able to find out, no, it has not been resolved.
There are a few “solutions” out there for using an old flash, with a new digital camera. Everyone points to these, and says, this will do it. But it does not, and there is a very good reason why. This next couple of paragraphs must be fully read to understand that……..
Photographers are a small sub-set of the population. Photographers who wish to use OLD electronic flashes on new digital cameras is a very small sub-set of photographers. Photographers who wish to use old FLASH BULB flashes on new digital cameras is so small that it is almost non-existent. The solutions that are found online, are designed for use of OLD electronic flashes, not old flash bulb flashes. There are differences that apparently do not allow the solution for one to be used to solve the other.
OLD electronic flashes use electronics themselves to close the circuit. They in turn use capacitors or other means to produce high voltage for the flash. Sometimes 250V or more, but the amperes are relatively small. Devices on the market and online designed for these flashes work fine for them. They do not work on a Graflite flash bulb flash. I have tried them. I have even spoken with the companies that produce them, and have been told by them their products are not designed to work, nor do they work with a flash bulb flash.
A flash bulb flash such as the Graflite only has 3 volts. But as I understand, it produces maximum amperage to trigger the flash bulb. Designed a long time ago, when all switches/triggers were mechanical, the full volts & amps travels through the cord and thereby the switch that triggers the flash bulb.
So, this is why the many people, over many months have had difficulty understanding why this seems to be so difficult You add in the fact that I am far from an electrical engineer, and this is why I seem to not be able to resolve the issue.
I have an OLD electronic flash, several in fact. I have successfully used them on my Canon 5D Mk III, which is a professional level camera. I even paid an electronics shop with an oscilloscope to test my most powerful OLD electronic flash. There series of tests produced the following results:
2-3 Milliseconds = Event Duration
10V = Average Voltage
2.1A = Average Amperage (4A Max)
So I know that my camera can handle this amount directly because I use it. But with the old FLASH BULB flash supposedly putting out up to 9A of current?????? I have heard many horror stories about people ruining their camera trying to do this. I do not want to have my $3,800 camera go down the drain.
Sorry for being long winded. Just trying to get the details out there. I will answer the other questions a little later. Thank you all!
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Hi FvM,
4) “, if the flash unit keeps the SCR and/or MOC3010 in triggered state, one should better use a regular optocoupler and transistor switch in combination with a pulse extension circuit”. I think that also. How about something like this? I created this earlier and abandoned it before testing. Plus I have all the parts. Obviously the actual cord to the flash unit replaces the 9V battery, and the test lamp is not used at that point.
5) “Can we catch an exact circuit schematic of the flash unit?”. Here is the overall schematic, from the Graflite Service Manual.
The “N” Extension is an option I do not use. The opposite end of the cord described at “SHUTTER” connects into the breadboard.
Hi barry,
“Attached is the way I would do this” Thanks Barry. I will look into this and see. I believe I posted my last post before I saw your last post. Does that information change your suggestion any? Thanks!