Use Old Flashes on New DSLR Cameras.


Introduction: Use Old Flashes on New DSLR Cameras.

This instructable shows you how to make a really easy and simple circuit, that protects your new camera from high trigger voltages in old flashes. It is completely safe and will not damage the cameras circuits!

It is better than those slave adapters that "look" for a flash, and then quickly activate the flash, since those adapters can be set off by other cameras. If you're at a party, that can be quite annoying.

Step 1: What You Need:

- general soldering equiptment
- a sense of electronics
- an Optocoupler with triac output (i.e. MOC3062)
- 2 capacitors ( 10 µF )
- 3 resistors ( 500, 1M, 30...80 ohms)
- a casing (optional, I got mine on ebay)
- a battery

Step 2: The Circuit:

The circuit is pretty simple and streight forward.

-The Optocoupler in the middle isolates the camera from the flash. If you don't know what an optcoupler is or what it does, check out wikipedia first

-R1 and C1 form a highpass. this is in case the output of the camera is a triac. with out the highpass, the current folwing through the led and the camera could keep the cameras triac open.

- The same goes for R3 and C2

- Now R2 is to limit the current though the LED of the optocoupler. you will have to adjust this depending on you optocoupler and battery you are using. Also keep in mind, that there could be a voltage drop inside of the camera which you have to consider! (it took me like 2 hours till I figured that out!)

Step 3: The Case:

I got my self an adapter, that would give cameras that only have a hotshoe an PC cord connector.
I got in on ebay:

I hoped, there was enough room inside to fit the circuit and the batteries.
Well the circuit barely fit, but the battery had to go outside...
if you squeeze everything into the case, please make sure that none of the highvoltage contacts or cables from the flas get to close to those that go towards the camera.

Also after everything is done, measure the voltage on the contacts that go to the camera before connecting it! Better safe than sorry!

Step 4: The Result:

ofter squeezing everything inside, I got a battery clip from an old motherboard and glued it to the side of the adapter.

And that is it. you can now connect pretty much any onld flash to you camera and don't have to worry about triggervoltages or anything!

Step 5: How to Use:

now you just put the adapter on the camera and either mount the flash on the adapters hotshoe or use the PC cord.
I like the PC cord alot, because it gives you alot of new lighting possibilities!

I hope you enjoy. If you have any questiones, just ask!



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    19 Discussions

    which pad to connect where.. please mention.. even the polarity of the capacitor..

    Thanks for the instructable, however I have a problem with my circuit. For the first 3 shots, it worked wonderfully, but after the 3rd flash, it is no longer working. Could you suggest something? I used an EL3021 optocoupler and the trigger voltage of the flash is 170V.

    1 reply

    turns out it was my fault because i had a chip with a maximum rating of 1A. I built in a thyristor and now it works perfectly :D

    Nice instructable!

    Looking at the circuit diagram, I think it could be unclear to some people which contacts on the hotshoe should be connected to where on the circuit diagram. If you can it might be nice to add a couple of diagrams showing exactly what goes where on the pad layout.

    I'm sure most folks will successfully work out that the centre contact and the outer shoe contact are the correct connection points, but it would help to clarify what the correct polarity is. Even if it doesn't matter, say it doesn't matter!

    Anyway, those are my thoughts. Hopefully you understand that I'm trying to be helpful; and not intending to knock you. It's a good project, but I'd rather nudge it towards being a *great* project.

    I would also love your circuit diagram to be sharp, but I'm not sure how to get this website to leave things in the right format myself. Whatever I upload it always seems to convert to JPEG and then compress it to within (or beyond) an inch of it's life ;)

    1 reply

    Thanx for the input! I will add the info on where to connect the contacts on the hotshoe!

    If you have a flash and you are wondering if it is safe to use, you need to know two things.

    1. What is the allowable trigger voltage on your camera (some may be has high as 24 volts but many are in the 5 volt range - old flashes can be in the 100+ volt range!)


    2. what the trigger voltage of your flash is,

    You can measure the trigger voltage with a multmeter. Let the flash charge and read the voltage that is between the center post and the ground on the side when you press the test button.

    Someone has created a chart of many common flashes and their trigger voltages.

    old flashes arc when fired .....which dolulob has mentioned it can and will most likely damage the cameras circuits......its a good idea but it should have a safe converter in it or some sort of arc protection as to not damage the camera

    1 reply

    the circuit has the optocoupler, which is probably the best device to seperate to circuits....

    Thanx! it's always nice to know your work is appreciated. I like your design.... gives me ideas.. maybe I'll have to get out my soldering iron once again! :)

    Nice! I've got an older Canan flash that I'd like to use on my new Canon S5. I think I'll try this.

    For those less electronically inclined, you can get the Wein device that imotor is referring to from eBay, sometimes for less than $50. It's call the Safe Sync.

    If you don't have an old flash already, you could buy a used one from eBay and apply this instructable for less than half. There are lots of used flashes available. See what I mean?

    A company called Wien makes a device like this, but it doesn’t require a battery.

    1 reply

    Righ i remember seeing it somewhere! Thanks for the info...but it costs 50$... mine is about 2$... there are ways to do it without a battery... however, they either don't use an optocoupler, and/or reduce the voltage of the flash using a zener-diode to power an optocoupler or fire a thyristor. I specifically wanted both circuits to be totally independant!!! I didn't feel comfortable reducing the flash's voltage with a Zener, because if a solder-connection comes loos, or the zener fails, it would expose the camera to the full voltage of the flash.

    Nice job, this is a great circuit, and technically worth alot of money, see new flashguns aren't as powerful and made of lower quality materials, but they're also obscenely expensive, the old ones are cheap at the minute due to their uselessness with new cameras...

    2 replies

    I think I have seen an adapter like this in an online store somewhere and it was like 60 bucks... so building it yourself is quite alot cheaper!

    Yeah, you could seel these in the 'ibles marketplace, there are a lot of camera users out there but not everyone is comfy with the electronics...

    well that's the thing, they probably DO work and everything seems fine at first, but you can and probably will, over time, seriously damage the camera's circuits.