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

Comments

[vricsi94]

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.

[vricsi94]

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

[LoonyLander]

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 ;)

[dolulob]

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

[Closer]

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!)

and

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.

http://www.botzilla.com/photo/strobeVolts.html

[kinekt]

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

[dolulob]

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

[robglinka]

Great work. I used your concept to build a disposable camera ring flash.

Here's some pictures from my flickr photo stream

Also, I stole the circuit from this guy: Optoisolated Circuit

[dolulob]

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! :)

[Josh_B]

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?

[imotor]

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

[dolulob]

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.

[killerjackalope]

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...

[dolulob]

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!

[killerjackalope]

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...

[LinuxH4x0r]

Very nice. I didn't know the old ones don't work

[dolulob]

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.

[LinuxH4x0r]

oh, ok