LED Camera flash gun circuit ideas

Thread Starter

sirch2

Joined Jan 21, 2013
1,026
I think I am struggling with semantics more than anything on this one hence a lot of Googling hasn't turned up very much by way of examples. In the UK we call them "flashguns" in the US they seem to be called "strobes" or "speedlights", I am referring to the the bright, short duration lighting devices that are used in photography. I would like to build a number of these and I am not looking for anything special or exotic, my reason for wanting to build rather than buy comes down to size, I would like them to be fairly small but beyond that no special requirements. My thoughts are that I can just build as many as it takes to get a reasonable amount of light for taking photos, in terms of flash duration they only need to be fast enough to freeze the motion of a person at about walking speed so I guess tens of milliseconds would be OK.

I have found one online article with a circuit and I would be interested in your thoughts on that circuit and if anyone has any other circuit ideas or can find links to such things on the web.
 

Reloadron

Joined Jan 15, 2015
4,591
Years ago I experimented with this but using Xenon tubes for the light source. I also had an old GENERAL RADIO COMPANY STROBOTAC 1531-AB which was great for playing around with photography. A Google of LED Strobe Circuits brought up some interesting possibilities, most of the circuits would need some modification. Something else to look for is Flash Slave Circuits where a flash is slaved to the camera flash. The important part being to get the slave in sync with the primary or master camera flash.

Never having tried this with a LED I am not sure how much light (brilliance) you can get pulsing a LED but I have seen some pretty bright LEDs. In the link you provided the author used a uC micro-controller to generate his pulse(s) but also mentioned the limits on the pulse width he could get.

Anyway, there are a few phrases you may want to try with Google.

Ron
 

Thread Starter

sirch2

Joined Jan 21, 2013
1,026
Thanks for the replies, I was thinking that an LED would make a smaller unit (think smartphone camera flash) than a xenon with associated capacitors and transformer
 

Reloadron

Joined Jan 15, 2015
4,591
Thanks for the replies, I was thinking that an LED would make a smaller unit (think smartphone camera flash) than a xenon with associated capacitors and transformer
Oh it will make for a smaller package as long as it gives the needed light intensity.

Ron
 

Reloadron

Joined Jan 15, 2015
4,591
I came upon this article Camera White LED Flash Illumination. The article makes for a good read on the subject and also gets into using the Agilent LED Flash Module which is a pretty nice high intensity LED module designed for flash photography. A Google of "Agilent LED flash module" brings up plenty of hits including more simple circuits. Maybe as winter gets here and my bike riding and shooting range time diminish I will get into this a little and play with the camera. I see the bright LWT67C LEDs available made by OSRAM through several distributors.

Ron
 

Thread Starter

sirch2

Joined Jan 21, 2013
1,026
Oh it will make for a smaller package as long as it gives the needed light intensity.
Reading around the subject I have seen it suggested that something like 10 to 40J is needed to make a photo with reasonable camera settings. As a sanity check: it is possible to take a photo with a 100W bulb lighting a room with say a shutter speed of 1/30s so that would be 3.3J if I am doing the maths correctly. Having now done those calcs, I am dubious about the schematic I linked above which only has 3000uF of capacitance which would store 1.3J. But thinking about it some more the 100W bulb is an incandescent and an LED is much more efficient so may be the schmeatic is not too far off. The author of that article uses it for close up macro photos.

There are MANY schematics around for stroboscopes:
Thanks Bertus, that rather shows the issue I was having sorting the wheat from the chaff, a lot of those are for strobes in the sense of regularly flashing lights/LEDs rather than single high power bursts on demand.
 

Thread Starter

sirch2

Joined Jan 21, 2013
1,026
I came upon this article Camera White LED Flash Illumination. The article makes for a good read on the subject and also gets into using the Agilent LED Flash Module which is a pretty nice high intensity LED module designed for flash photography. A Google of "Agilent LED flash module" brings up plenty of hits including more simple circuits. Maybe as winter gets here and my bike riding and shooting range time diminish I will get into this a little and play with the camera. I see the bright LWT67C LEDs available made by OSRAM through several distributors.

Ron
Thanks again Ron, seem to have missed your later post whilst typing my response above.
 

bertus

Joined Apr 5, 2008
20,105
Hello,

As you might have noticed, a lot of the schematics use the 555 in the circuit.
This will allow you to disable the flashing using the reset input.

Bertus
 

Reloadron

Joined Jan 15, 2015
4,591
During the years when I was into playing around with strobing swinging golf balls. tennis balls and ping pong balls I also played with light color. An incandescent lamp will produce a warmer light while a while LED a cooler light. The LED being closer to a camera Xenon flash or daylight. The light color being measured on a Kelvin scale. Incandescent was warm, around 3200 Kelvin and flash was much cooler around 5500 Kelvin.The three primary types of color temperature for light bulbs are: Soft White (2700K – 3000K), Bright White/Cool White (3500K – 4100K), and Daylight (5000K – 6500K). The higher the Degrees Kelvin, the whiter the color temperature. This has an effect as to how the subject looks in an image.

Depending on the camera the user has a variety of controls. Things like shutter speed and aperture come into play. What I frequently would do is use what we called a B or Bulb setting simply holding the shutter open while I strobe the subject. Anyway, the links I posted will hopefully be of some interest.

Ron
 

RichardO

Joined May 4, 2013
2,268
What I frequently would do is use what we called a B or Bulb setting simply holding the shutter open while I strobe the subject.
You can get some very interesting effects by doing this in a dark room and selectivley "painting" the object in the photo with the strobe.
 

Reloadron

Joined Jan 15, 2015
4,591
You can get some very interesting effects by doing this in a dark room and selectivley "painting" the object in the photo with the strobe.
Yes, and another fun thing was using a dark room and literally painting a subject with light, anything from a flashlight to a pointing laser would yield some interesting results. This was also true of using human subjects.

Ron
 

Thread Starter

sirch2

Joined Jan 21, 2013
1,026
Just feeding back on initial tests. I built the circuit linked in the OP, here are the results from an initial test from a 7W COB LED driven at 12V. the flash is about 4' from the white piece of paper. In the first the flash fires, in the second it does not, camera settings kept the same in both.

IMG_6675.jpg IMG_6676.jpg

The point of this circuit though is really to drive the LED at much higher power, I just need to rig up a higher voltage supply.
 
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