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01-08-2010, 05:50 PM   #1
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What exactly is trigger voltage?

I'm looking for a technical explanation. Where does it come from and what does it do? I have a K7 an old sunpak 333D flash and Cactus V4 trigger. I figure I'm safe as long as I don't physically mount the Sunpak directly to the hot shoe. Am I wrong? I mean I can't fry my camera wirelessly, can I?

01-08-2010, 06:53 PM   #2
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When you trip the shutter with a flash attached to the camera, a circuit is completed to allow the flash to fire. The voltage of this circuit is the trigger voltage.
01-08-2010, 07:03 PM   #3
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The trigger voltage is when the flash is all charged up, ready to fire, on, is the measured voltage from the hot shoe center pin--on older flashes the ONLY pin--to ground, which is the side of the hto shoe. On older film cameras, the hotshoe was activated by a mechanically operated switch, very low current, but they would handle the high voltage--nearly 300V on some old flashes.

All modern film and digital SLRs use a solid state device of some sort to trigger the flash. To continue the long answer, "you are screwed" because none of the manufacturers typically bothered to care about you being able to use older, high voltage trigger type flashes.

EVEN WHEN A CAMERA is rated for HV, such as my Canon Xt and 40D, I DO NOT USE HV flashes because I figure that you are stressing that switch device , rating or no. The camera is expensive to repair, much more so that junking and old flash, or simply finding a used LOW volt. flash, which are prolific. Most Vivitars I've run across for example, are low volt. trigger

Even if you find a cheap flash that's dedicated for the wrong camera, it's easy--in most cases, to pull the hot shoe apart, and disconnect all but the center pin---turning the flash into a "non dedicated" unit that you can use on any camera.
01-08-2010, 10:37 PM   #4
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Most new digital cameras with a hot shoe use a thyristor capacitor switching circuit. They are typically spec'd to tolerate a 6V to 12V trigger voltage from the flash unit depending on the make/model of camera. Therefore, it's strongly recommended to avoid directly attaching an older flash unit if you don't know it's trigger voltage is in the range acceptable to the camera. If in your unawareness you attached a higher voltage flash, it may or may not permanently damage the camera's switching circuit, depending on how high the voltage and if used repeatedly. However, the end result is that it can burn out the thyristor capacitor. I've heard that some camera's can handle a higher trigger voltage if you use the PC connector socket on the camera meant for studio flash direct connection, if it has one, instead of triggering via the hot shoe.

If you want to use an old flash unit in the hot shoe, the best approach is to purchase a Wein Safe Sync module that attaches between the flash's hot foot and the camera's hot shoe. The Safe Sync has an optical isolation switching circuit built inside of it to buffer the camera's switching circuit from the high voltage of the flash. I've used one for years on several older Sunpak flash units and it works great with Pentax and Canon cameras. It also has a PC socket to use with studio flash or flash units requiring a PC cord connection and gives you the same "safe" optical isolation that way too.
For some weird reason, they don't seem to work consistently with Nikon digital cameras. (I guess there's the Nikon way and then everyone else...maybe they just want you to use their SB series flashes only...anyway, Nikons are not as robust as most other cameras in that regard)

BB

01-08-2010, 11:03 PM   #5
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To add to the confusion

QuoteOriginally posted by BB_Zone28 Quote
Most new digital cameras with a hot shoe use a thyristor capacitor switching circuit. They are typically spec'd to tolerate a 6V to 12V trigger voltage from the flash unit depending on the make/model of camera. Therefore, it's strongly recommended to avoid directly attaching an older flash unit if you don't know it's trigger voltage is in the range acceptable to the camera. If in your unawareness you attached a higher voltage flash, it may or may not permanently damage the camera's switching circuit, depending on how high the voltage and if used repeatedly. However, the end result is that it can burn out the thyristor capacitor. I've heard that some camera's can handle a higher trigger voltage if you use the PC connector socket on the camera meant for studio flash direct connection, if it has one, instead of triggering via the hot shoe.

If you want to use an old flash unit in the hot shoe, the best approach is to purchase a Wein Safe Sync module that attaches between the flash's hot foot and the camera's hot shoe. The Safe Sync has an optical isolation switching circuit built inside of it to buffer the camera's switching circuit from the high voltage of the flash. I've used one for years on several older Sunpak flash units and it works great with Pentax and Canon cameras. It also has a PC socket to use with studio flash or flash units requiring a PC cord connection and gives you the same "safe" optical isolation that way too.
For some weird reason, they don't seem to work consistently with Nikon digital cameras. (I guess there's the Nikon way and then everyone else...maybe they just want you to use their SB series flashes only...anyway, Nikons are not as robust as most other cameras in that regard)

BB
I believe that the PC sockets still use the old type points and may be able to handle old flashes.... don't blame me if they don't though.....
20D - flash sync circuit voltage limit - Pro Photo HOME
I believe this would be the orig ist-D and the k-7.
The rest (hot shoe) I probably wouldn't trust. Really annoys me that the camera manuf. are so tight lipped regarding such a simple spec.
Confusion reigns supreme:
20D - flash sync circuit voltage limit - Pro Photo HOME
01-09-2010, 06:17 AM   #6
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Original Poster
Good answers about the definition of trigger voltage. I suppose I should have asked this yes/no question more directly:

I have a K7 an old sunpak 333D flash and Cactus V4 trigger. I figure I'm safe as long as I don't physically mount the Sunpak directly to the hot shoe. Am I wrong? I mean I can't fry my camera wirelessly, can I?

WD
01-09-2010, 06:57 AM   #7
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You are safe with the wireless trigger. You could fry the trigger if that does not tolerate high voltages. Check with a multimeter.
01-09-2010, 07:06 AM   #8
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Or use a WienSafeSync.

I have te same problem, and bought me a WienSaveSync. It converts the high(er) voltage to a safe 6 volt. I use this as long as i don't know the hotshoe specs of my K7
https://www.pentaxforums.com/forums/pentax-dslr-discussion/85528-k7-maximum-a...r-voltage.html

Depending on you're flash you can use a cable version or a hotshoe version


Wein | SSPC Safe-Sync | W990515 | B&H Photo Video


Wein | Safe-Sync Hot Shoe to Hot Shoe (SSHSHS) | W990560 | B&H

I use the cable version with my Metz 45 CT-5 flash


Last edited by Sakura; 01-09-2010 at 07:14 AM.
01-09-2010, 07:39 AM   #9
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I'm surprised that a 45CT-5 requires this. I have a 45CT-1 that can be used directly (I have a so-called safe serial number above 534 000).

Or was it a matter of better safe than sorry.

Did some research (source FAQ: Metz )

QuoteQuote:
Can the mecablitz 45 CT-1 also be used with the new autofocus cameras?

Regretfully, the Metz mecablitz 45 CT-1 does not yet have the connecting capabilities of the Metz SCA adapter system. Consequently, no corresponding adapter is available for combination with autofocus cameras. The Metz mecablitz 45 CT-1 can therefore only be connected to such cameras with a standard synchronising cable.

Furthermore, it is necessary to note that Metz mecablitz 45 CT-1 units featuring a model number that is smaller than 534 000 are fitted with a so-called high-voltage ignition circuit. These flash units must not be directly connected to modern cameras as this could even damage the camera!

All other flash units of the Metz mecablitz 45 CT and 45 CL series feature a low-voltage ignition circuit in keeping with the current standard.
01-09-2010, 07:43 AM   #10
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You can probably forget about the Safe-Sync; according to the Big Reference Table of Strobe Trigger Voltages, the Sunpak 333D uses a paltry 2.0V to trigger. I think the max for DSLRs is about 6-12V; with older cameras using mechanical switches, there was pretty much no limit. Some flashes trigger at 300V+. Those old, classic Vivitar 283s can go as high as 600V!

So, yes, you can mount 333D on your K7, on the hotshoe. NOTE: I'm not legally responsible if anything goes wrong...
01-09-2010, 10:06 AM   #11
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QuoteOriginally posted by lithos Quote
You can probably forget about the Safe-Sync; according to the Big Reference Table of Strobe Trigger Voltages, the Sunpak 333D uses a paltry 2.0V to trigger. I think the max for DSLRs is about 6-12V; with older cameras using mechanical switches, there was pretty much no limit. Some flashes trigger at 300V+. Those old, classic Vivitar 283s can go as high as 600V!

So, yes, you can mount 333D on your K7, on the hotshoe. NOTE: I'm not legally responsible if anything goes wrong...
+1 agree.

(10 Char.)
01-09-2010, 02:20 PM   #12
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It is indeed a "better safe than sorry" because of total lack of info on the X-contact specs of the K7.
I don't even know or the relative low voltage of 24 volt of the CT-5 can blow the tyristor of the K7.
As i wrote in the other topic i started about the max trigger voltage, my former K100D could handle 300 volt (not enough for the old CT-1 but more than safe enoug for the modern Metz 45 series)

btw
Originally i owned a "low-serial-number" CT-1 so, no way i will connect it to my cam

I bought my present Metz 45 CT-4 and CT-5 at ebay for some 50 euro each
Replaced the original Nicad's in the accu with brand new ones, with triple the capacity of the original ones.
Really, the CT5 rulezzzzzz

Last edited by Sakura; 01-09-2010 at 02:26 PM.
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