Hi All,

I am trying to set up a charging system for my wife's off camera flash units she uses in her home studio. She has three flashes that charge off 4 "AA" batteries that I have eliminated so they can be wired direct to the charger. The charger I am using is a 6 volt 1 amp trickle charger but when all three flashes are used the charger shuts down for about 30 seconds and then resets (overload protection). I have a 6 volt 6 amp charger that I can use but when the flash capacitors reach full charge the voltage increases to a point that the flash units get hot.

What I need is a schematic and parts list for a voltage regulator that will handle the draw from all three flash units and keep the output voltage at around 6 to 6.5 volts.

Any suggestions are welcome.

Thanks in advance,
John

 

Here's your easiest and least expensive solution.

Go back to using the trickle charger, but get these:
http://www.radioshack.com/product/i...1&filterName=Type&filterValue=Power+resistors
Two bucks. Take the two 10 Ohm resistors, and connect them in parallel.
This results in a single 5 Ohm resistor. 6.5v / 5 Ohms = 1.3A maximum current.
Your little charger should keep working with it's load limited.
Then connect the resulting 5 Ohm resistor in series with the connection to the flash units.

 

Sgtwookie,
Thanks for the reply and I will give it a try, but I guess I should have also said I'm trying to decrease the recycle time of the flashes by providing as much available amperage as possible. With the 1 amp charger with all three flashes the charge time is about 20 to 25 seconds and in the realm of photographers and women that's an eternity. I have seen some regulator schematics using 3 pin ICs which look fairly simple to put together but I'm not sure which one to use and how to calculate for the companion resistors.

The no load voltage on the 6 amp charger is around 9 volts.

Again thanks for the reply
John

 

Sure, there are really simple 3-terminal linear regulators available.

The most common versions are good for about 1.5A. You apparently want 6A output.

It's tough to do that with commonly available (Radio Shack) parts. You really need a switching regulator, with a large capacitor on the input.

However, you could build this from Radio Shack parts: (note: V1 and D01 are internal to your 6v charger)

Or this:

In either case, the 2N3055/MJE3055 transistor will need a large heat sink due to the power being dissipated in it as heat. A heat sink scrounged from an old PC would be a good candidate.

There are switching regulators available, but that would be an intermediate level project.

I don't know how much experience you have with electronics, but I can only assume that you are a beginner.

 

Sgt,
Thanks again for the quick reply and suggestions. There are readily available 1.5 amp chargers which might be better than what I am currently using, could you point me to a schematic for that size power supply. I have experience putting together circuits from schematics just never had time to get into designing my own.

Thanks
John

 

Well, now I don't really know what you want to do.

If you want to build something, then go ahead and build it.

You gave some requirements, and I thought you wanted to use what you had.

Why don't you state all of your requirements for what you want to accomplish, and then we can go from there.

You would be much better off to simply use an off-the-shelf 6v switching supply, or simply add a 6v lead-acid battery in the equation with your trickle charger.

 

Sgt.,
Sorry for the confusion. I did want to try and use what I had but I am not opposed to upgrade if the results would be better "Any suggestions are welcome.".

It never occurred to me to use a 6 volt battery inline with the charger, that may solve the problem very easily.

Thanks for the help.
John