Direct-Drive 445 Host

[LarryDFW]

Pyro;

Ran it for a solid 15 minutes last night doing a light show on the grass in the back yard.

The finned heatsink was barely warm to my hand.

Seems to be dissipating the heat effectively.

Here is a photo of the nylon belt case & charger:

LarryDFW

 

[Wallydraigle]

Can you expound on the direct drive thing, or link to somewhere that explains it? You're just connecting the laser diode directly to the battery and that's that?

 

[qumefox]

If I had to hazard a guess. I would say it's not really direct drive, but that he's using the LED driver that came in the host instead.

I was planning on trying it with the tank007 hosts I ordered whenever they and my 445's show up, since according to website for them, those particular LED drivers are constant current at 1000ma. I just don't know what kind of voltage compliance range they have or how clean the output really is, so i'll probably check one on a dummy load watching it with a scope before I try a real LD.

 

[Cenobite9]

I've never tried using the existing host drivers but I have run a LOC red directly off a RCR123A battery in a Dorcy host before. It worked without any problems... I guess these 445 diodes could be run the same way but they are a bit more expensive than the LOC Red diodes should it not work I had always wondered if the LED drivers in the flashlights could actually run these diodes effectivley.

 

[Wallydraigle]

I don't know, in another thread I think he said he was just using a resistor to drop the voltage a little or something.

 

[qumefox]

I don't know, in another thread I think he said he was just using a resistor to drop the voltage a little or something.

Oh.. Well, resistors don't limit voltage, they limit current, but how much depends on the voltage. So as the batteries die, the current limiting changes too. It's why direct drive really isn't advised with batteries.

 

[Wallydraigle]

Well, I'm just going by what he said here, which is why I wanted more info. What makes this not go *poof*?

 

[qumefox]

The casio 445's are pretty tough to begin with, and as long as you seriously underdrive the diode, they'll usually live.

 

[Cenobite9]

The casio 445's are pretty tough to begin with, and as long as you seriously underdrive the diode, they'll usually live.

Hope that statement goes for A130 diodes as well... I'm driving an A130 at 600mA so I hope I get good life out of it.

 

[CrazyMonkey]

Direct drive should mean using only a resistor to limit current.

 

[qumefox]

Hope that statement goes for A130 diodes as well... I'm driving an A130 at 600mA so I hope I get good life out of it.

Well if your using a real driver, you can go a lot higher than that. The problem with direct drive is that you never know what what current it's running at since it changes with the battery voltage. Plus there's nothing to stop voltage spikes from the switch, etc.

 

[LarryDFW]

My "direct-drive" has no resistor at all ...

other than some small resistance in the host.

It has been operating happily for several hours.

There is absolutely no reason it should not continue to operate for many more hours.

While it most likely has the highest efficiency of any 445 build...,

it just happened to come together that way.

I have been using it for a "lumia" projector effect recently.

LarryDFW

 

[qumefox]

You sir, are very very brave then. heh.

 

[Wallydraigle]

Wow. I really want to try that, but I don't want to blow my diode.

 

[plexus]

Wow. I really want to try that, but I don't want to blow my diode.

yeah. that can be messy without a towel

 

[LarryDFW]

Wally;

As long as you have a good heatsink,

the diode will be fine.

I've checked several 445nm diodes, and all of them were fine for direct drive.

LarryDFW

P.S. No voltage spikes from a DC battery.