photo flash connectors

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pankau42
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photo flash connectors

Post by pankau42 » Sat Dec 17, 2005 1:47 pm

Hello, new to the forum, love Nuts&Volts.
Anyone know where I can get "pc" type photo flash connectors, male and/or female? I am building a safe sync for a friend with a D-Rebel that can only handle 6V on the hotshoe. I'd like to find something that is mountable in a small enclsure rather than tear apart some cables and throw something together. I've looked in Newark, Digikey etc... but those places don't seem to carry these types of connectors.

thanks.

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jwax
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Re: photo flash connectors

Post by jwax » Sat Dec 17, 2005 7:51 pm

Welcome nerdy.
Perhaps if you described what connector type you were looking for, instead of "6 V on the hotshoe" for your D-Rebel, someone could offer assistance. (Personally, I'm not following your banter!)
Describing what you're after is the key to getting solutions here.

jimandy
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Re: photo flash connectors

Post by jimandy » Sat Dec 17, 2005 8:08 pm

Googling turns up that ”D-Rebel” is a camera and “hotshoe” is the means of attaching a flash unit on top with a slide like mount that provides the contact to supply the trigger voltage to fire the flash Other flash units get their trigger voltage from a cable that plugs into a small jack on the camera body. I thinks he’s looking for a source of that type of connector. I still can’t figure “safe sync”.
"if it's not another it's one thing."

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jollyrgr
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Re: photo flash connectors

Post by jollyrgr » Sun Dec 18, 2005 8:34 am

I'll throw in a couple observations; some speculation as well....

Cameras (the "professional style") have several connector styles that trigger the flashes. A HOT SHOE (that also holds the flash itself) is usually on top of the camera and has two or more connections available. The center connector and "shoe" holder are what trigger the flash. The other connections can be used to alert the camera to the flashes settings, control the flash intensity (duration), and a host of other parameters. A SYNC connector is one that is used to control flashes not attached to a camera. When you see a photographer with a camera and a cable coming from it to the "umbrella" lights, the cable is usually connected to the SYCH port of the camera. There are a couple styles of this connector. The PC SYNC connector is a small "coaxial" style connector that a cable plugs into. On other cameras it resembles an AC plug. At the flash end it is common to see a standard 1/4" phono plug.

The xenon flashes used in photography are high voltage (200V to 400V) discharge tubes. To "activate" the tube a very high voltage (4000V to 8000V) pulse is developed on the outside of the glass tube. This pulse is generated by use of a step up transformer or trigger coil, sort of like an old time igition coil. In some cases the same 200V to 400V used to power the flash tube was also used to pulse the trigger coil directly. Thus you'd have 200V or so present at the hot shoe or sync port.

This was fine when cameras were strictly mechanical; but digital cameras this high voltage could be a problem. (Yes, the high voltage COULD cause arching in the metal mechanical contacts.) In modern flashes there is a low voltage (24V or less; mostly 6V) trigger circuit. But for modern cameras to work with classic flashes, you need some sort of isolation device; i.e. a "SAFE SYNC". It is this device I believe that Nerdy is trying to build. Here is an example of what one type of these devices looks like:

<img src="http://www.bhphotovideo.com/images/larg ... 227625.jpg" alt=" - " />

These devices are not cheap (over $50) so you can understand why Nerdy wants to build one. These are probably not much more than an optoisolator or some sort of thrystor. In bulk they could be built for about $5.

As far as where the parts come from, good question. My guess is that they are custom designed and there is not a huge market for what you are doing. You could try someone like SWITCHCRAFT and see if they have a line that is not published in their catalog. (I designed a aviation intercom. The headphones have a standard 1/4" mono or stereo phono jack. The microphones used in aviation have a 3/16" stereo phono plug. Switchcraft was able to supply me with that special jack. I still had to go through one of their resellers but at least they were able to provide me with the part numbers so I could special order the plugs and jacks. While Switchcraft made the parts and they were available, this was not something any vendor had listed in their catalogs nor was it something that was listed as a standard part. When I called a product support tech she knew right away what I needed and looked up the part numbers with ease.)

Quantum Insturments ( http://www.qtm.com ) might be willing to tell you where they get their parts, but I highly doubt they will be of much help.

I hope this is helpful.
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pankau42
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Re: photo flash connectors

Post by pankau42 » Sun Dec 18, 2005 9:28 pm

Mr Roger.. whew.. yes I think you see where I'm coming from. I have a circuit prototype that uses MOC3012 Fairchild triac driver as the isolator. Works very well with flashes since most are SCR (half of a triac) for the trigger circuit.
Like you say these "PC connector" parts are in low demand.
I'd really like to make something that is more reliable than the safe sync made by Wein. It uses a bit of parasite voltage from the flash to power the camera side. If the impedance seen by the flash is not very high it may not fire on cue. Case in point... I connected my fluke scope meter to the flash terminals and it refused to fire after the first flash. Input impedance to the meter was too low and the flash would not reset. Evidently an "open" condition must be very close to infinite. When I added a 10Meg resistor to the scope lead, it worked.

I'll check out SWITCHCRAFT for parts.

thanks.

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