How To Build A Flash (With An Optical Slave)
Usually where danger is involved we simply say something like "please know what you're doing" or "If you need to ask how this is done, this is not for you", but for this particular piece, I thought a bigger warning should be in place. And I darn well mean it.
WARNING: This article involves dealing with High Voltage, up to 300v, which is stored in big capacitors. THIS VOLTAGE CAN KILL YOU. Never touch any of the components and always discharge the capacitor before working on it. Always keep in a well insulated project enclosure.
BY FOLLOWING THESE INSTRUCTIONS YOU AGREE TO BE THE ONLY RESPONSIBLE FOR ANY DAMAGE THAT MIGHT BE CAUSED BY DOING SO. WORK CAREFULLY AND FOLLOW WARNINGS.
If you think this warning was not bold, big or strong enough, please read it again. (I do realize this may end up in a loop for folks who think this is as easy as a learn how to solder project. That's the point)
This article will help you understand the basics of how a flash circuit is working, and the second part will show you how to build your own optical triggered portable flash rated at 50 watt/seconds!
How Does A Flash Work In A Nutshell?
There really is no explanation of electronics without a scheme, so we placed a scheme below. While it does not go in depth about each of the parts it explains in a nut shell what's its name and what it does. The magic of it, of course, is that you can create quite an effective burst of light, from a few 1.5V AA batteries.
The power from a low voltage battery (1) is fed into the inverter transformer (3) through a transistor (2), that is switching the current on-and-off, in a few Kilo-Hertz frequency (thousands of times per second).
The transformer (3) outputs high voltage of about 300 volts to a big capacitor (4) which will charge during a few seconds and serves as an energy storing device.
Meanwhile (as they say in comic books), the small trigger capacitor (5) is being charged. As soon as a burst of light is detected (from firing another flash) the photo-transistor (6) is translating the light-burst to a small voltage, that will trigger the Trigger Coil (7). The coil then produces a short pulse of very high voltage (6000 volts), which will ignite ionize the Xenon gas inside the Flash tube (8). Once ionized, it will draw all the energy stored in the big capacitor (4) and will output this energy in the form of light (the final flash).
What Are The Steps To Building A Strobe?
The first step is to go back and read the warning at the top of the post.
Then, start with deciding how much power (or how much light) you want your flash to output. Since the power to the flash tube is derived from the big capacitor (4 in the previous drawing), you control the power by controlling the size of that capacitor. Here is how to calculate the capacitor size.
As all things energy, flash output works kinda like exposure on P mode. You start with a base value for flash power, say 100w/s flash (or 100 Joules). To get this kind of flash you need to feed the bulb from a 2000uF capacitor at 330v.
Cut the capacitor in half, and you get half the power: a 1000uF capacitor will give you about 50w/s.
Actually, as a thumb rule, every 1000uF capacitor added will give you about 50w/s of energy.
Of course, once you have the power calculated you need to decide on a bulb capable on carrying that amount of power without exploding (yes Exploding).
Unlike incandescent lamps, flash tubes are rated for their MAXIMUM energy.
That means that a flash tube that is rated 200w/s MAX, can be fed with energy anywhere from 0 to 200 w/s. This exact lamp with a 1000uF capacitor will output 50w/s, and with FOUR(4) 1000uF capacitors will output 200w/s – its maximum allowed energy per flash.
So to recap, the capacitors are defining the flash energy, and the lamp has to have a compatible rating.
The rest are fixed components that have little dependency on the flash output which you wouldn't have to change, we are listing them here as a reference.
We like to use the XFT-1610 as the inverter transformer, and TC-36 as trigger coil. They are very compact and always work great.
The following circuit diagram shows an exact basic circuit. It works reliably and gives good results, accepting 4xAA batteries as a portable power source, or a 5v transformer for external power, and delivering 50 w/s of light.
This basic circuit is great, because you can easily modify it – add more capacitors for higher flash power, change the flash tube to fit in reflectors, or even connect several flash tubes in parallel to place them in a circular reflector and create a Ring-flash.
Just a small reminder, the most important of course is, staying alive. Please take great care when trying to assemble this high voltage circuit.
After powering it, never touch any of the soldering or the components, always use an insulated plastic project box, and always use a volt meter to verify that the big capacitor is EMPTY before you are working on the circuit.
GOOD LUCK !
About The Author
Avner Richard is a fashion photographer and an electronics tinkerer. You can find his photography here, and his tinkering here.
Get the DIYP greatness via RSS, newsletter and Twitter
Connect with the community: Facebook Page, Discussions
Share Ideas, Setups, Images and Projects on DIYP's Flickr, visit Readers Photos
Comments
capacitor safety
from "The Technicians 10 Commandments" -
"Beware the lightning that lurketh in the undischargeth capacitor least it rise up to smite thee and cause thee to sit down in a most untechnician like manner!"
OMG
ROFL
Great article, but...
How would someone go about wiring it to be triggered from a hotshoe or PC connection?
Hotshoe or PC connection
You would need to replace or add to the Optical Trigger circuit. On the Schematic where you see the "TOPS-050", that is the Photo Transistor circuit. You would need to insert into that part of the circuit a trigger which pulls up the transistor on the MCR100L. This would in turn fire the Trigger Circuit (the TC-36) which would fire the flash. Same goes for if you wanted to add a manual momentary push / fire button. You would jumper the transistor to pull that leg up when the momentary button was pushed and POP goes the flash.
"which will ignite the Xenon
"which will ignite the Xenon gas inside the Flash tube"... I think you might have meant "will ionize the xenon gas."
Is this a kit or did the
Is this a kit or did the author fab the circuit board?
http://www.xenonflashtubes.co
http://www.xenonflashtubes.com/optical-flash.html
XFT-1610??
I cant find the XFT-1610 trafo... any substitution or specification of it?
Cool kit
Its a cool kit. But I am a bit confused on the Flash Tube power.I want to make a 200 w/s flash by adding 3 more capacitors to the kit. My questin is, is the kit's flash tube capable of 200 w/s? Or do I need to use a bigger tube?
The http://xenonflashtubes.com/strobe.html site says it is 25W. Not sure how it translates to MAX w/s.
Thanks,
VV
Answers
ERIK:
actually shorting the MCR100's gate leg (G) to the Cathode (K) will trigger the flash.
but you have HIGH VOLTAGE THERE. (low current though)
you would need to add an optocoupler for example
BIEL:
Here you go: XFT-1610 (click)
VV:
The kit's lamp won't take 200 w/s.
you need the FT-R50. also consider charging time will be 4 times longer.
you can rather use 4 kits in parallel, with 4 of the stock lamps, total will still be 200w/s, with the same charging time. (or 2 kits @ 100ws each)
Does that mean the kit lamp
Does that mean the kit lamp takes 100 w/s?
And how much does FT-ST-S40w take? It says 40W.
Thanks,
VV
The spiral lamp could take
The spiral lamp could take 100w/s.
the U shape lamp (stock lamp of the kit) would take 50w/s
Thanks!!!
Thanks!!!
I almost died because of this
I almost died because of this shit!!!!!!
It shook me seriously until the flash stopped. Damn, what a fool I've been!
You have to be extremely
You have to be extremely careful when dealing with high voltage.
I'ts not complicated at all. very easy.
you just need to know what you are doing and always stick to the safety rules.
they are all written. if you got high voltage juice - you did something wrong.
The coil then produces a
The coil then produces a short pulse of very high voltage (6000 volts), which will ignite the Xenon gas inside the Flash tube (8). Once ignited, it will draw all the energy stored in the big capacitor (4) and will output this energy in the form of light (the final flash).
I'm sure you mean ionize/ionized, right?
right
right
Substitute photo transistor
Can you substitue the photo transistor with a small jack so it can be fired by radio/PW? Would it also be possible to install a switch to choose between the photo transistor or radio.
Please get the units right...
Hey, this is a highly technical project. And an exceptionally cool one! And we have to trust you that you got the numbers right so it does not blow up in our face. So please get the units right or you won't earn my trust (and I will have to calculate the numbers for myself...)
There is nothing like W/s (watt / s)... this would be like an acceleration... because P (Power in the unit Watts) is w / t (work, in Joule divided by time in seconds). So W/s would be J/s^2...
The formula P = w/t can be rearranged to W = P*t which is in units: J = W*s or short Ws (Wattseconds). Maybe this sounds like nitpicking... And I know that almost no journalist on this world can get the Energy / Power stuff right. But you're not the common journalist, are you?
that flash . . . .
Have read the comments, with interest. One, in particular, had me rolling with laughter- "been there, done that" (fat smack from a loaded capacitor - Oooops!). I found the circuit diagram and explanation of working very interesting - but I will stick with my Yongnuo 460-II speedlite, and I'm happy that I now understand how it works. Great article - and the warning is fine. Thanx
BOM for build???
Would it please be possible to get a BOM with the part numbers for the components from a supplier like Mouser.com (or some other location) for these items to do the build? I've spent the better part of the morning searching and have found many of the items, but some I just can not seem to locate! :( The TC-36 / Trigger Circuit for example seems to not match up to any sort of ISO part that I can find whatsoever. Perhaps I'm just looking in the completely wrong place, or Mouser.com doesn't carry the part (I'd be shocked as they seemed to have stocked everything else electronics wise I've ever built but it's certainly possible) but a search for the part seems to only point back to www.xenonflashtubes.com/tc-36.html for the part sourcing.
I'd like to fab my own boards to create a number of flashes, as well as a ringflash, and would prefer to also use this as a good project for teaching how to do board fabrication with a few members of my photog co-op... and having the scematic really helps, but a few of these parts are key and seem to be missing direct lookups to local suppliers. :-(
Unique components
Hello,
Thanks for your interest, TC-36 and XFT-1610 are unique components that are used for Xenon flash application only. it's quite rare to com across such unique components at local suppliers, as most of them are only sold to manufacturers of eqipment, etc...
you could use any trigger coil and any inverter transformer with similar specification.
we didn't invent anything. but it is still the cheapest and easiest source available for those unique ones
mouser.com + trigger coil
mouser.com + trigger coil
Control and housing
1. Is there a way to house this so there's no exposed parts?
2. Is there a way to add controls so you can get 1/2, 1/4, 1/8, 1/16 and maybe even 1/32, 1/64 and 1/128?
Cascade of capacitors
This possibility exists. And it can be done in different ways. The easiest would be to install a cascade of different capacitors. Take a 470uF instead of 1000uF and you have about 1/2 of the power. 220uF would be about 1/4 power and so on.
So for example have 22uF, 22uF, 47uF, 100uF, 220uF, 470uF. And have a switch to connect them/disconnect them parallel.
the 22uF gives you about 1/50 Power, two of them about 1/25. Add the 47uF you you get about 1/10. Add the 100uF and you're on about 1/5. Add the 220uF and you have about 1/2. And together with the 470uF you're on full power (for your flash). I know, that if you add up the capacities you won't get 1000uF but 881uF. But in my oppinion it's close enough.
Keep in mind that the power should be switched when all the capacitors are empty. Otherwise there are high currents over the switches when switching the capacitors on or off which can short the life of the switches.
Another possibility is to do it like most modern flashes are doing it by switching off the flash lamp after a certain time. But this would take some more parts and a lot of thinking to get it right.
Is there a kit for a more
Is there a kit for a more powerful flash setup? I figure if I were to build something I might as well build something absurdly powerful. That is not to say 50ws is weak but from a quick google 50ws is roughly something between a 430ex and a 580ex and it would be nice to have some cheap maybe... 100ws strobes
More power!
The Power is linear to the capacity of the main cap. Which means, that you would just have to double the capacity (i.e. putting a second one in parallel to the first one) to get doubled power output. But keep in mind that this will only give you a bost of 1.41 (sqrt(2)) in the guide number.
So with a simple formula that only gices you a rough estimate I get about GN 28 out of the 50Ws version and about GN40 from the 100Ws ( sqrt(w)*4 ) (metric). If you wanted to double the GN you would need to quadruple the capacity (and take a lamp that can handle that power). And also keep in mind that the loading times are rising linearly with the capacity. So quadruple the capacity to get dpubled GN and you have also a four times longer loading time. Better take 4 of the kits and use them in parallel. This gives you more flexibility.
I'm planning on building a few cheap halogen floodlights to use them as case with a reflector for the flashes. You get these floodlights for about $10. Plus the kit and battery holder for about 30$ and you have a nice portable flash unit. Than put something that transmitts some ir light on the hot-shoe of my camera and you can start to play strobist...
working on it too ! you can
working on it too !
you can use the same kit meanwhile, adding a second 1000uF capacitor and a second flash tube in parallel, this gives you 100ws
Powering with higher voltage
Is it possible to be modified so instead powering with 6 v DC to power with 220v AC , wouldn't capacitor loading time rises down ??
This would require circuit
This would require circuit re-designing. And the capasitor is being charged at 300V DC allready. I think it would be possible to do 230V -plug to this flash, it would just require correcty fitted trasformer and rectifier.
220v conversion
to convert this to a 220v project one would require a 220v to 12v transformer a rectifier and a 5volt 3 amp regulator and its not that difficult at all .. the down time of the flash will be seriously less but one also needs to take into account the heat generated when taking multiple shots in quick succession thus choice of housing the unit in a box with ventilation is of importance ... just a suggestion :) wicked project tho .. thanks
almost forgot one would need
almost forgot one would need a smoothing capacitor before the 5v regulator which is of the 7805 series :)
joules and watt-seconds
I was quite confused by the use of the "w/s" unit in this text. I believe it's a typo.
The abbrevation for watt is an uppercase W, and 100J = 100W·s (100 joules are 100 watt seconds and certainly not 100 watts *per* second).
Strobe using a 750W linear flash tube
I wish to build my own strobe using a 750W linear flash tube,working on mains (230V), triggering with an external TTL pulse, for a variable flashing rate. Need help bulding the circuit and deciding about the components.
Drawing above
Would someone mind showing me the numbers on the transformer pins in the drawing above? Thanks.
XFT-1610 datasheet
please check the datasheet for pins and diagram
http://www.xenonflashtubes.com/XFT-1610-6v.html
Charging time??
Someone know charging time for a 50 W/s kit??
Post new comment