Graflex.org Forum Index Graflex.org
Get help with your Graflex questions here
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Graphlite Flash Trigger Voltage
Goto page 1, 2  Next
 
Post new topic   Reply to topic    Graflex.org Forum Index -> Flash Help
View previous topic :: View next topic  
Author Message
btvarner



Joined: 05 Oct 2017
Posts: 9

PostPosted: Thu Oct 05, 2017 11:57 pm    Post subject: Graphlite Flash Trigger Voltage Reply with quote

Was wondering if anyone knows the voltage that travels through the connector cable when triggering a Graphlite Flash?

I have such a flash. Works perfectly on my Speed Graphic. I want to try (Do not ask why) to use this flash on my Canon DLSR. I understand the limitations, but I would like to try anyway if I can find this answer.

Hence the question. Thanks!
Back to top
View user's profile Send private message Visit poster's website
Markus



Joined: 13 May 2015
Posts: 14
Location: MA, USA

PostPosted: Fri Oct 06, 2017 6:03 pm    Post subject: Reply with quote

I am certainly not an electronics expert ... but the Graphlite simply applies its battery voltage to the flashbulb to fire it. So when you add up the battery voltages (3 x 1.5V), that should be the most that can show up at the connector cable?

I would think the warning about using old flashes with new cameras would apply mainly to old electronic flashes which charge up their capacitors to a high voltage and may let that reach the connector cable.

You will have a sync problem with the flashbulb and only be able to use slow shutter speeds, but I guess you are aware of that.
Back to top
View user's profile Send private message Visit poster's website
btvarner



Joined: 05 Oct 2017
Posts: 9

PostPosted: Fri Oct 06, 2017 6:46 pm    Post subject: Graphlite Flash Trigger Voltage Reply with quote

I understand,
I believe that you may be correct. BUT !!!!!!!!!!!!!!! I am not sure I am willing to put the electronic circuitry of my Canon 5D Mk III on the line to test this theory until I receive some further confirmation on this subject. You know what I mean?
Back to top
View user's profile Send private message Visit poster's website
45PSS



Joined: 28 Sep 2001
Posts: 3558
Location: Mid Peninsula, Ca.

PostPosted: Fri Oct 06, 2017 7:25 pm    Post subject: Reply with quote

On pages 5 and 6 of the Graflite service manual http://www.southbristolviews.com/pics/Graphic/manual-pdf/GrafliteService.pdf
is the schematic of the Graflite. The shutter contacts are in series with the battery positive and will feel the full battery voltage + the full circuit current when triggered. The 2 cell Graflite will experience 3 to 5 amps of current and the 3 cell will experience 7 to 10 amps of current upon tripping the shutter.
Use a flash adapter such as https://www.bhphotovideo.com/c/product/89977-REG/Hama_HA_6950_Universal_Flash_Adapter.html
with your DSLR. M type flash bulbs have a 15 to 17 millisecond rise time to usable light output and burn for an additional 10 to 15 milliseconds.
http://www.donsbulbs.com/bulbs/g623/l/ge1954/08.gif
Visit the library at http://www.donsbulbs.com/cgi-bin/r/t.pl/library1954ge.html for more flash bulb information and the
site information at https://graflex.org/flash/technical.html and https://graflex.org/flash/

Use shutter speeds of 1/30 second or slower when using flash bulbs.
_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.
Back to top
View user's profile Send private message Visit poster's website
btvarner



Joined: 05 Oct 2017
Posts: 9

PostPosted: Fri Oct 06, 2017 7:51 pm    Post subject: Reply with quote

Thanks for the feedback. Great info!

On pages 5 and 6 of the Graflite service manual http://www.southbristolviews.com/pics/Graphic/manual-pdf/GrafliteService.pdf
is the schematic of the Graflite. The shutter contacts are in series with the battery positive and will feel the full battery voltage + the full circuit current when triggered. The 2 cell Graflite will experience 3 to 5 amps of current and the 3 cell will experience 7 to 10 amps of current upon tripping the shutter.
Ok, electricity is not my long suit. But as I understand it amps is the volume of current & voltage is the pressure of current? So I am not clear: 1.5v (D Cell) + 1.5v (2nd D Cell) + 5 amps = 3 volts + ? volts. This to me seems important because the DSLR camera rating using a PC connection is 250v Max on my Canon 5D Mk III. On the surface this seems well within the handling capability, but not sure I am calculating it correctly?

Use a flash adapter such as
https://www.bhphotovideo.com/c/product/89977-REG/Hama_HA_6950_Universal_Flash_Adapter.html
with your DSLR. M type flash bulbs have a 15 to 17 millisecond rise time to usable light output and burn for an additional 10 to 15 milliseconds.
http://www.donsbulbs.com/bulbs/g623/l/ge1954/08.gif
Understand. In fact I just received a Wein Hot Shoe Safe Sync from B&H for this purpose. It has a PC connection built right into this Hot Shoe. However it does not trigger the flash? I can go into that in more detail if anyone is interested.

Visit the library at
http://www.donsbulbs.com/cgi-bin/r/t.pl/library1954ge.html
for more flash bulb information and the site information at
https://graflex.org/flash/technical.html and https://graflex.org/flash/

Use shutter speeds of 1/30 second or slower when using flash bulbs.
Understood, thanks!
Back to top
View user's profile Send private message Visit poster's website
45PSS



Joined: 28 Sep 2001
Posts: 3558
Location: Mid Peninsula, Ca.

PostPosted: Fri Oct 06, 2017 8:49 pm    Post subject: Reply with quote

Current in a circuit equals the voltage applied divided by the resistance of the circuit. As metals get hotter their resistance decreases. 2 D cell batteries connected in series as in a flash case are 3 volts.
Copper wire at room temperature is .006 ohms for 18 gauge wire. Being a 2 cell flash uses copper strips of 3 to 4 inches the contacts and connecting strips provide about .002 ohms of resistance. I do not know the internal resistance of flash bulbs but suspect it to be 1 ohm or less.
3/1.02= 2.94. As metals get warmer their resistance decreases, and current will increase. When resistance gets low enough the laws get violated and thermal runaway occurs resulting in currents that far exceed the formula.

Now your camera may be designed to handle high voltages but it cannot handle more than a few milliamps of current.

Does your safe sync fire an electronic flash connected to the PC socket?
Electronic flash require only a very brief connection to fire. Leaf shutters provide a contact duration of .5 to 1 millisecond, an electronic flash will fire with a .1 millisecond contact.

Electronic flash work on high voltage, low current. Flash bulbs work on low voltage, high current. If the camera has a PC socket it will likely handle the Graflite, ask Cannon to be safe.
_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.
Back to top
View user's profile Send private message Visit poster's website
btvarner



Joined: 05 Oct 2017
Posts: 9

PostPosted: Fri Oct 06, 2017 9:13 pm    Post subject: Reply with quote

Thanks for the lesson. I do appreciate it.

Does your safe sync fire an electronic flash connected to the PC socket?
Yes. As a more detailed explanation: The Safe Sync will fire everything but the Graphlite. All possibilities on either side have been checked.

The Safe Sync will:
-When attached to the 5D it fires any flash (PC or hot shoe) I a place on it except the Graphlite
-The PC connections were using the same cord I normally use to fire the Graphlite flash

The Graphlite Flash will:
-Fire off as expected when attached to the Speed Graphic (Different cord)
-Fire off as expected when attached to my Kodak Medalist (Same cord)
-Fire off as expected when red test button is pushed on the Graphlite

So, for some reason the Safe Sync does not like the Graphlite. I had hoped that this would be the simple solution, since that is the purpose of the Safe Sync is to reduce the trigger voltage to below 6 volts. But maybe the amps is still too high and will cause it not to fire?


Electronic flash work on high voltage, low current. Flash bulbs work on low voltage, high current. If the camera has a PC socket it will likely handle the Graphlite, ask Cannon to be safe.
I agree. I think it will. I also did call Canon. They were very nice, but stated that such connections are not recommended. Would not give me a good enough feeling to be positive about it. The manual says that the PC connection on the 5D is rated at 250 volt max. However I do not know the rating for high current/amps. I just really hate to use a $3,500 camera to test the theory.........
Back to top
View user's profile Send private message Visit poster's website
45PSS



Joined: 28 Sep 2001
Posts: 3558
Location: Mid Peninsula, Ca.

PostPosted: Fri Oct 06, 2017 9:30 pm    Post subject: Reply with quote

Early electronic flash (1950's -1960's) applied 450 volts to the flash sync contacts. Modern flash still use 350-450 volts to the flash tube but the trigger circuit has a buffer so that a lower voltage is sensed at the trigger contacts.
Current was less than .1 amps in the early days and is now in the .001 amp range.

You can always use "Open Flash" with the 5D.
Open the shutter on B, trip the Graflite via its test button or a remote cord, close the shutter. Ambient lighting can be controlled to allow a 1 to 15 second exposure time easily and the trip the shutter-fire the flash-close the shutter can be done in 1 to 2 seconds with practice. You do not have to waste flash bulbs practicing either.
A remote trigger cord for the Graflite will have a household plug on one end and a push button switch on the other, easy to make.
_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.
Back to top
View user's profile Send private message Visit poster's website
btvarner



Joined: 05 Oct 2017
Posts: 9

PostPosted: Sat Oct 07, 2017 1:50 pm    Post subject: Reply with quote

Yes thanks, I know I can set the flash off independently. That just seems to limit creativity too much.

It seems the issue involves the way that any HSHSB triggers are constructed. They seem primarily meant to address early strobe flashes that produced high Voltage. The Graphlite instead produces high amperage which the devices are not designed to handle???

I am beginning to see why I have been unable to find a successful method to achieve triggering this particular type bulb flash anywhere on the internet. I do think it is achievable, but needs paid electrical engineer and some paid lab time to create the correct device to achieve the goal..............
Back to top
View user's profile Send private message Visit poster's website
45PSS



Joined: 28 Sep 2001
Posts: 3558
Location: Mid Peninsula, Ca.

PostPosted: Sat Oct 07, 2017 9:18 pm    Post subject: Reply with quote

I've been out of electronics tooooo many years to hazard a guess. A fast acting relay with the primary connected to the camera and the secondary contacts to the Graflite will do the trick.
http://www.mouser.com/
there might be a chip capable.
_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.
Back to top
View user's profile Send private message Visit poster's website
btvarner



Joined: 05 Oct 2017
Posts: 9

PostPosted: Sat Oct 07, 2017 11:53 pm    Post subject: Reply with quote

I have tried a couple of times with both Canon and Wein. Attempted to find out from Canon what the output volts & amps or milliamps were when the Canon 5D MkIII triggers a flash using the PC port. They said that was proprietary and would not provide. Attempted to find out from Wein what the input and output volts and amperage was for their Safe Sync trigger. The persons I spoke with did not seem to know and did not try to find out.

I am not going to attempt a direct connection via the camera PC port as I believe it will fry the camera circuit board.

So, yes I understand that a relay built in line with the PC cord should work. I assume it should be relatively simple to use an extra couple of PC cords to splice in the extra connections. The goal would be to just connect the PC cord from the Graphlite into the board with the relay output. Then another PC connector from the input side of the relay to the cameras PC port.

I have linked to a schematic. Please understand that I am not an expert on electricity, nor on schematics, so if you see mistakes please let me know. My biggest question is what size relay to obtain for this purpose.

I relay output needs to be able to handle the 3 volts (From my multimeter) and the approximately 2.94 amps of current. The relay input needs to be what the Canon camera uses to trigger the PC connection. I assume it is very low, but I do not know how low. Has to be under the Canon battery amount of 7.2 volts and 1800 m/Ah. But how much under. I would guess that I should go with the least a middle of the road input…….

So, do they even make relays with this type difference in input/output volts/amps? Looking for more feedback here. Thanks!

http://brucevarner.com/DLSR%20PC%20Connector%20to%20Graphlite%20Flash%20Schematic.jpg
Back to top
View user's profile Send private message Visit poster's website
45PSS



Joined: 28 Sep 2001
Posts: 3558
Location: Mid Peninsula, Ca.

PostPosted: Sun Oct 08, 2017 6:10 am    Post subject: Reply with quote

I haven't worked in electronics since the late 1980's. I'm not up to date on components currently available.
A flash socket connects the leads together to trigger the flash. In the case of PC sockets the outside sleeve is connected to the camera case which is ground or battery negative. Some cameras may connect battery positive to the camera case. The center contact of the PC socket is connected to the camera case via a mechanical switch or electronic switch by the shutter action. In the case of a hot shoe the center contact gets connected to camera ground via electronic switch while other contacts act as a thyristor cutting off light output as directed by the camera.

In place of a relay a SCR may do the trick. The SCR is a high current device controlled by a low current. Anode +, Cathode - (flash and camera), Gate to PC center contact.
Camera - and flash negative will have to be the same battery polarity.
There may be newer components that are better suited to the task.
_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.
Back to top
View user's profile Send private message Visit poster's website
btvarner



Joined: 05 Oct 2017
Posts: 9

PostPosted: Sun Oct 08, 2017 2:06 pm    Post subject: Reply with quote

Thanks! Makes sense. Another good idea to look at. I am going to wait a few days before diving into this. I have scheduled some electrical circuit training videos on

https://www.lynda.com/

to make sure I feel comfortable with the theories behind what I will be doing. I am sure I could successfully complete such a simple circuit, but want to know more about what is behind the process. I will pick it up quickly I am sure.

Anyway, as I will start to accumulate the parts necessary to accomplish this during this time frame, I do have a general question.

When I purchase a relay or SCR for that matter, I am confused as to what size is required. Meaning, do I:
Just ensure that the piece is rated something above the need? Or do I have to worry about buying a piece that is rated too high, and therefore may not be able to say trip the switch because too little current is actually coming from the camera?

Hope that makes sense. Thanks!
Back to top
View user's profile Send private message Visit poster's website
45PSS



Joined: 28 Sep 2001
Posts: 3558
Location: Mid Peninsula, Ca.

PostPosted: Sun Oct 08, 2017 7:23 pm    Post subject: Reply with quote

A relay may have to be powered by a separate battery with the camera completing the circuit and a resistor to isolate the camera/limit the current.
Similar for a SCR. The relay contacts and SCR should be able to handle at least 5 amps but more than 10 would be overkill. The lower the trigger current the better for the SCR and the lower the current to trip the relay the better. There may even be a solid state relay that is suitable.
_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.
Back to top
View user's profile Send private message Visit poster's website
btvarner



Joined: 05 Oct 2017
Posts: 9

PostPosted: Mon Oct 23, 2017 5:12 am    Post subject: Reply with quote

Ok,
This thread has gone quiet because I decided to take a break and learn more about electrical circuits before proceeding. Took a couple of online electronics courses and studied up on the subject. Here are the results.

I had 2 goals in mind:
1) Do NOT fry my Canon 5D Mk III DLSR camera.
2) Build (As there are none out there that I found) a small circuit that would protect the DLSR from high voltage & amperage when connecting a Graflite Flash Bulb flash to the DLSR camera.

Below is the link to an image of the proposed circuit for this purpose. I have completed proof of concept by using a common switch to serve as the DLSR PC port to successfully trigger a relay that in turn closes the circuit on the Graflite flash, successfully lighting the flash bulb. The relay serves to protect the flashes high current from the low current circuit used to switch the relay. While at the same time keeping the volts that will cross the cameras PC port to less than 5V and at about 70mA.

http://brucevarner.com/Final%20Graflite%20to%20DLSR%20Circuit.jpg

Please let me know if you see any discrepancies in my circuit design. I want to be absolutely sure that this will protect me DLSR. Canon freely gives the maximum voltage allowed at their PC port as 6V, but refuses to provide me with a maximum amperage allowed.......
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    Graflex.org Forum Index -> Flash Help All times are GMT
Goto page 1, 2  Next
Page 1 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group