DIY - Flash PC Cord for cameras without hotshoe / PC cord jack using fiberoptics - General Chat - CHDK Forum

DIY - Flash PC Cord for cameras without hotshoe / PC cord jack using fiberoptics

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Offline PhyrePhoX

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for offcamera lighting (this means the flash is NOT directly under or above or near the lens) and subsequently way more beautiful pictures it is neccessary that one can "ignite" an external flash even though it is not directly connected to the camera. DSLRs all come equipped with a hotshoe and a PC Cord Jack, which enables you to either mount a flash on the hotshoe ("external flashes" normally are huge, so they arent really that near the lens when mounted on the hotshoe) or use a PC cord to sync it remotely. Some more expensive Bridge/Compact cams from canon feature at least a hotshoe, for example the g9 and the s5is. There also are adapaters you can use to mount on the hotshoe that emulate a pc cord jack - for cameras that dont sport one natively.

neither my s3is nor my a620 have a hotshoe or pc cord jack. What am i to do?

You can either buy flashes that have a built-in optical trigger that triggers when you internal flash fires, or you can buy a small gadget that will give your external flash this capability. I happen to have such a small gadget and an old slave which triggers fine. The Problem is - you need to have "optical contact" between your cameras flash, which sucks when for example you have the external flash BEHIND your subject and your interal flash set to low output - the external flash will most likely not trigger.

So here's the fun part: I happen to work in an IT-department, and we had some spare optical-fibers in the trash bin yesterday and i had the idea to use that as a "pc-cord". Works flawlessly, and i didnt even affix it to the camera and flash firmly, i just held them together with my hand. the flash was set to low output, the optical fiber around 5 meters long - the external slave fired!
This has two advantages: I can completely cover my internal flash (i only want to use the external one on my subject!) and the external flash ALWAYS sees the internal flash. Also, i can connect several flashes this way.
Disadvantage: optical fibers are quiete expensive (unless you work in an IT dept, dunno the exact prices though) and they are quiete easily destroyed when bent too far or stepped on. Also, 5 meters arent that long (will buy maybe 10 meters soon).

But all in all, this is a very reliable solution for us cheapskates who dont own expensive cameras to begin with :D

Pics will follow, dunno when though, as i didnt assemble anything yet (wont be very sophisticated as well).

ps: triggering an external flash only works when you can set the flash power manually, not automatically (as the camera will always fire a preflash, which will trigger the external flash - camera sees the external flash, recalculates exposure and leaves you with a WAY TOO DARK picture, funny, huh :D)

p.p.s: explanation of pc cord: Flash connections

by the way, check out Strobist - a VERY good resource when it comes to good lighting, tutorials etc.
« Last Edit: 11 / September / 2008, 08:51:02 by PhyrePhoX »


Offline Pauls9

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Re: DIY - Flash PC Cord for cameras without hotshoe / PC cord jack
« Reply #1 on: 10 / September / 2008, 07:04:01 »
That's a really cool idea.




Re: DIY - Flash PC Cord for cameras without hotshoe / PC cord jack
« Reply #2 on: 10 / September / 2008, 07:05:05 »
PhyreFox; good idea.
You may want to have a look at this link:
DIY Live  » DIY Archive   » DIY Disposable Camera Flash Slave
The constructor uses a programmable PIC chip as a delay trigger.
The software is on the web page.
A 3 metre fire optic audio cable may be ideal.
A slave hood design is at this site:
Michael McGraw Photography Online Galleries : photos : Foam Flash Diffuser- powered by SmugMug

I found a lighting trigger at: 
Lightning Activated Camera Shutter Trigger
The circuit could be used as a fibre optic amplifier if the light level is too low.

ePanorama has some interesting information on fibre optics - Links

This web site has a lot of information on camera flash units and modifications:
Notes on the Troubleshooting and Repair of Electronic Flash Units and
Strobe Lights and Design Guidelines, Useful Circuits, and Schematics

« Last Edit: 10 / September / 2008, 11:53:46 by databoy »


Offline PhyrePhoX

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Re: DIY - Flash PC Cord for cameras without hotshoe / PC cord jack
« Reply #3 on: 11 / September / 2008, 08:40:06 »
thanks for the links!

1st link: i hate soldering, as my chubby hands always seem to break something :D
2nd link: flash diffusor is cool, will probably build one soon.
3rd link: soldering again, yuck :D
4th link: solid gold, thanks :)
5th link: not too bad as well, much to read there, but for now i will experiment with my fiber optics

i found me a longer cable, thinner and MUCH longer, i think it is 20 meters or longer. i still havent assembled anything sophisticated, i just did this small test:

turn on camera, pop up flash, set flash to "always".
load chdk, load intervalometer script, set to "shoot once every 10 seconds"
take one end of the optical cable, somehow "lean" it into the flash of the camera (taping would be better, but i just made this simple test)
take the other end of the cable, go to another room with it, or leave the flat if your flat isnt big enough (well you can also stay in the same room, but then the test isnt really proving that the cable was used)
hold the end to the slave flash's "trigger diode" - now watch a burst of flash triggered every 10 seconds. i didnt even have to hold it directly above/in front the diode, it was even working holding it like 5 cms away from it, just pointing it in the general direction.

- it doesnt really matter how long the cable is, my guess is that you can even use 50 m or longer. now you may ask: what would i need that for? well for example you are shooting using zoom, and you want to light your subject - there is NO way the built-in flash will reach the subject, so you either need one of those radio controlled pocketwizards (which wont work with our cheap cams) or a pc cord (which also doesnt work with our cheap cams, plus they come in like 5 meter long - too short!) or the optical fiber cable. also you sometimes need a long cable when for example you are shooting someone with a wide lens and the flash is behind the subject - where to hide the cable? having a long cable allows you to go "outside of your cameras radius", if you catch my drift.
- since i just made a short test with "holding in the general direction of the trigger", i can safely assume that once i build a construction that allows me to attach the cable to both camera and flash securely, tightly & "unbreakable", there is no way the flash will NOT trigger, also my construction will not have to break anything in the shell of the flash or my cameras body (since i dont have to affix the cable directly IN the camera's flash or directly ONTO the trigger of the external flash)
- it is cheap and reliable (just checked for prices of optical fibers - like 5 bucks for 10 meters on ebay, which will be sufficient i guess)
- using this construction will put an end to the firing of MY external flash because someone elses camera is using flash.
- using this construction you can make sure your subject is lighted by the external slave flash and the ambience only, not by your camera's flash.

will post video + pics here soon i guess.

by the way: after some research i found something that MIGHT be of use for us cheapskates: radiopoppers. These "transfer" the optical signals from the expensive wireless TTL flash/cams via radio signals over a great distance. here's the catch: 180 $ each and also the radiopopper jr. (which will be the gadget helping us) is not released yet, but are supposed to weigh in 25$ only (the normal radiopoppers most definitly only work with expensive lighting gear/cameras). here's an article about the "normal radiopoppers": Strobist: RadioPoppers: Not Just For Wireless TTL
« Last Edit: 11 / September / 2008, 10:07:15 by PhyrePhoX »



I can solder and read circuits, but I cannot program to save my life. In most cases it is the board layout which kills the project.

I have been thinking about a similar system for a while. The length of the fibre optic cable would not be a problem as long as there is some light. A photo transistor amplifier circuit will do the rest. If you know anyone who is throwing away defective DVD players, grab them as there are some useful components in them. In some players the fibre optic board is a small sub-board with a photo transistor and sometimes a line amplifier. Defective PIR security sensors are another source of components; especially mains types used to switch on lighting. They usually use a capacitor as a voltage dropper. The actual circuit runs of 12 volts. It is a matter of removing the mains wiring and wiring 12 volts to the unit.

I tried 555 timers but found the common variety are not stable on switch on. CMOS varieties are stable but for people who lack soldering skills a PIC chip or a PICAXE kit PICAXE is the way to go. Minimal soldering and very simple board layout. Also PICAXE have BASIC software which can be adapted.

A 3 metre audio optical cable would be ideal. All you need is the flexibility of using a camera without anything getting in the way. The control unit could even fit in your pocket. Cabling used to wire security alarms is small and inexpensive. Relay outputs on the unit could be used to control whatever lighting is necessary for the photo session.

My camera is a S3IS. As I understand it; in the flash mode, the camera pre-fires the flash to measure the level of lighting to set the ISO level. Can CHDK be programmed to fire the pre-flash only. If it can, it opens the possibilities of turning on mains halogen lamps located elsewhere. I am thinking of pressing the shutter, fire the pre-flash, that would give enough time to switch on halogen lamps, then 2 seconds later take a shot. After the shot the halogens would switch off.

I have an oscilloscope, digital multimeter and prototyping board. I have downloaded most of the PICAXE technical and software manuals. I have a 3 metre audio fibre optics cable. Thinking about it; all I need is a light sensor, an amplifier chip, a PICAXE chip and a relay. I live in Australia; there are a number of companies which have pre-packaged kits. I will look through the catalogue and see if there is a simple kit which is easily adaptable.               

I have to do some more thinking; I will post back with my ideas/results.


Offline PhyrePhoX

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well i figured that the length of the fibreoptical cable really isnt an issue, so i wont be needing a light amplifier, after all - the flash is an really strong light source. if 100 meters is too long (for the light - let's leave the use for a photog out of this) i assume it is because i didnt really "catch" all the light of my cameras flash and sent it into the cable (same applies to the other end). so the only construction i will need is "how to affix the cable to both camera flash and slave flash".
i think i will buy one of those cheap optical triggers - i can cut it, open it, i can basically do anything with it becoz it is cheap. i could use that to have a cable attached to it forever, so i dont have to care about that end of the job (literally).
For the cameraflash i have to make something i can take off and put on without problems, but it must always remain steady and should not fall off itself. hm.
well, using preflash to fire all the stuff only makes sense if all the stuff would light up instantly - and stay lit for a further 1/1000 second, because after the preflash there is a "realflash". this would give us basically TTL (through the lens), which would totally rock - but i doubt it is possible, as with most flashes they cant recharge that fast.
the preflash is fired so the camera can calculate exposure and/or flash strength. if you use auto-flash, the camera flashes preflash, looks at the output and then fires the real flash, all in an instant. If you fire your slave flash on the preflash, your picture will actually become darker, as the camera sees the slave-flash, uses that into calculation (cranks exposure way DOWN) and by the time the "real" photo is taken, it is way too dark because your slave-flash hasnt recharged in that 1/1000 second (i dont know if that the actual time, but it must be somewhere around that value). I just noticed my cheap slave flash has a setting that ignores a preflash and only fires on the realflash (nothing fancy, the trigger only triggers on 2nd flash, no matter how stronge etc).
One thing i learnt from - automatic settings are bad when it comes to lighting. You want light that is highly reproducible, and you can only get this when you set the flash to manual (which mine unfortunately cant do - means that if the ambience light changes - which i cant control - the flash output changes) AND the camera to MANUAL mode. fun thing is, you control your final lighting of the picture with aperture (flash & ambient light) and shutter speed (only ambient light), a thing i have not taken into consideration before reading up on Strobist. it's all clear to me now - the flash fires so fast, that the shutterspeed almost is of no concern to it, you can control the flash only by changing aperture (or dial down the power on the flash manually, or use a diffuser, or back up the flash from your subject).
So what it boils down to is that we dont wanna use the preflash, instead you have to set your camera to manual flash mode (only available in m, tv & av mode) and use yourself and the histogram as a lightmeter. since we are talking cables, this method isnt for snapshots in the wild anyways, so you can afford taking some testpops, right.
anyhows, let's see who builds something first :D



I do not know if the project below has been posted before.

AI-1 ("All-in-one") Remote

It looks interesting. Maybe someone can adapt the project for CHDK use.



I have another method which may be of interest. I was playing around with the half shutter press in a semi-dark room. It occurred to me that when the shutter is half pressed, the camera makes the shooting sound. The AV connector is next to the camera speaker. The S3IS 4 pin AV connector is available. If I heat shrink a small microphone to a blank AV connector and wire it to a voice operated relay, the unit should operate on a half press. A ready to assemble kit is available in Australia. Details are at Sound Voice Activated Relay Switch. The actual circuit diagram is on the bottom of page as a download PDF. K126.pdf   


Offline PhyrePhoX

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well but what would you need it for? so that at half press the slave flash goes off? please explain.?

the AI-1 sounds interesting, but as far as i can tell suitable for the expensive range of cameras only?



I like the fibre optic idea; I could not any find suitable components, locally, to try the fibre optic approach. The local electronics suppliers do not stock the components I required and I did not want to go mail order at this stage. Also, I could not find a good way of adhering the fibre optic cable beside using velcro stuck on the camera.

I have all the vox components in my electronics kit. I thought I would have a go at the vox approach. That way if the concept works other people could replicate it. 

I have built a vox prototype to prove the concept. The unit I used was a small 12volt anti-shake device used in vehicle alarms. The circuit design works similar to the vox details I posted. I removed the tamper sensor and wired in an electret microphone in its place. The audio trigger works reliably every time. I monitored the signal on an oscilloscope. Voice can be picked up from half a metre but the camera speaker tone can only be picked up when the microphone is directly mounted over the camera speaker. The pulse out works well. The next step is, I will build a prototype of the vox unit and compare the results.

The av jack is an unsuitable mount; it turns off the display. The next step is to build a camera adapter bracket; built a self contained unit which activates a wireless remote, and mount all the electronics on the bracket.

My application is for indoor photography. I have tried shooting photos at a number of indoor functions with the S3IS. The flash on the S3IS is useless in a lot of applications. I want the unit to switch on mains operated halogen lamps conveniently located in the room. The shutter half press is suitable for my application. The lights will switch on for a predetermined amount of time. Take the shots and then switch off the lights.

I am a qualified electrician; therefore working with mains equipment is not a problem. In Australia, twin 1000 watt halogen lamps with a stand can be purchased for around $30. The lights can be located at convenient places in a room. Leaving the lights switched on permanently is inconvenient; therefore activating the lights with the camera is a good way of getting the necessary shots.

I realise that there are many people who have no experience with mains equipment. 50 watt, 12 volt halogen lamps are quite affordable. It is quite easy to built a similar 12 volt system operating off a sealed 250 volt to 12 volt garden lighting transformer.

The unit can also be used for portrait or glamour shots. I have seen easy to built light curtains posted on various sites on the net. A light wall to diffuse the lighting can be made from cheap cloth.

I know I am crossing the line into professional photography. In my case I do not have the disposable income to buy pro equipment. This way is a cheap cost effective way of experimenting with indoor lighting and indoor photography.     
« Last Edit: 14 / September / 2008, 00:29:39 by databoy »


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