Anybody care to help me understand about making an LED flash unit for a camera?

[musiclear]

I'm needing to rework a flash system for a project I am working on and want to use a LED for a flash unit triggered by the hot shoe on a Nikon camera.

I understand most LED flash units use 3-5volts and I plan on using two AA batteries which will produce about 3v.


I also understand that the shoe is not a voltage supplier, but completes a circuit to ground allowing flash unit voltage to travel through the camera.

The 3v I intend to use will be no problem.

I am wondering if I need any circuitry at all? In other words, have the batteries connected to the led all the time and use the ground in the camera shoe to complete the circuit and fire the LED when I take a picture?

Am I thinking about this OK or am I missing something?

[Æ]

I'm needing to rework a flash system for a project I am working on and want to use a LED for a flash unit triggered by the hot shoe on a Nikon camera.

I understand most LED flash units use 3-5volts and I plan on using two AA batteries which will produce about 3v.


I also understand that the shoe is not a voltage supplier, but completes a circuit to ground allowing flash unit voltage to travel through the camera.

The 3v I intend to use will be no problem.

I am wondering if I need any circuitry at all? In other words, have the batteries connected to the led all the time and use the ground in the camera shoe to complete the circuit and fire the LED when I take a picture?

Am I thinking about this OK or am I missing something?

Wouldn't it just be simpler to buy a flash? Buy a cheap one and take it apart? Personally I don't think that LED flashes are fast enough, but then again what do I know. You might try inquiring at a few of the more technical photography websites.

[tomzarbo]

The thing with LED's is that they are all over the place as far as color temp output. Some are bluish, some greenish, some bright white and others are more daylight looking. Every LED flashlight I own has a slightly different look. I don't think your pics would have much of a chance of looking normal unless you really did some research on what types of LED's had the most natural output.

Are there any LED flashes on the market now? (I'm not a camera guy) I see a few video lights, but not really any flashes during a 20 second quick search.

Also, I think the output of LED's diminish with lesser voltages, with a normal flash the batteries charge the cap which does the lighting, but with what you're contemplating, the batteries would be the only power source... I would imagine that the color temp would change as the batteries loose power.

Maybe this is one of those things that it's pretty hard to DIY? Seems like LED's would be a good candidate for flashes, but maybe there is a good reason they're not used....Keep digging, though maybe you can MacGyver something together!

TomZ

[Sydney]

I don't think that LED flashes are fast enough,

My understanding as well, compared to the commonly used Xenon.

[musiclear]

I agree and have heard that LED flashes are a little slow. But, take a look at your cell phone? They all use them and to a pretty weak degree, but I don't need a lot of strength. Also, you can choose your color spectrum. 6k is natural and can be compensated for by the settings on the camera. I am sure it can be done simply and without a lot of costs. It's just a matter of finding the diagram and board and parts and making it. Simple right?

[wogg]

I agree and have heard that LED flashes are a little slow. But, take a look at your cell phone? They all use them and to a pretty weak degree, but I don't need a lot of strength. Also, you can choose your color spectrum. 6k is natural and can be compensated for by the settings on the camera. I am sure it can be done simply and without a lot of costs. It's just a matter of finding the diagram and board and parts and making it. Simple right?

In your phone, the LED is compensated for in timing, the LED flash is on well before the shutter is opened. On a typical hot shoe camera it won't have that timing built in so it's likely to be too late for the LED's.

On the technical side, there are a couple things to consider:
First you will have to know what kind of current that shoe can sink. You'll be attempting to dump the LED current into it, which it may not and probably will not like at all. It's likely intended for a small TTL or logic signal, so you'll need a current buffer or isolator circuit, possibly a pull up resistor, all of which I can't confirm because I'm not familiar with the details.

Second, you'll need current limiting resistors in series with the LED's calculated with the battery voltage less the LED voltage drop divided by the desired LED running current.

[Whitneyville1]

Is this a film camera or an electronic camera? In either case, the shutter sync contacts are made to take up to about 1000 volts but at micro-amps. You'll cook the shutter contacts with the current even a low-power LED will draw. Also, your shutter sync speed will be extreamly low because the the "lag time" it takes the LED to come to full brightness. So you're probably limited to an 1/8th second or even slower. KEH camera has used electronic flash units from about $10.