*Updated Photos* $16 DIY 200mW 650nm [Pic Heavy]

[Spyro]

One more question XD Does this laser need a heatsink? Cuz i think its pretty :lasergun:

 

[Hiemal]

Yes, your laser module will need a heatsink. My PHR-803T build runs at around 90 mA and gets a tad warmer than I'd like. I'm sure that at 300-500 mA it's gonna heat up a lot more.

 

[Fretwrecker94]

One more question XD Does this laser need a heatsink? Cuz i think its pretty :lasergun:

Before I sold the last one i made, also figured out the duty cycle is about 30 seconds on and 30 seconds off. 330mA for an LOC type diode is nothing to overkill with a heatsink.

 

[SparkyHt]

I thought I'd take a crack at this build...seemed cheap enough. Of course when I tried to remove the little driver pill, the leads going to the LED just popped off the circuit board and rendered the driver useless. I examined it to see if I could repair it, but the little traces snapped where they go into the epoxy blob. I tried to be gingerly about it, but it just disintegrated in my hands. The host is perfect though, I'll just have to pop a little more for a driver to fit behind everything.

 

[Fretwrecker94]

I thought I'd take a crack at this build...seemed cheap enough. Of course when I tried to remove the little driver pill, the leads going to the LED just popped off the circuit board and rendered the driver useless. I examined it to see if I could repair it, but the little traces snapped where they go into the epoxy blob. I tried to be gingerly about it, but it just disintegrated in my hands. The host is perfect though, I'll just have to pop a little more for a driver to fit behind everything.

Yeah I was lucky enough to get 3 of these in a row with intact drivers. The last 2 I got in my order both came with broken drivers. They wouldn't turn on. But they're cheap enough so its no big deal

 

[dlipford370]

I'm having a go at this one. We all need to try and find drivers that work for our lasers like you did, maybe even start a database of all the "flashlight/led drivers" that work for lasers!

I'm curious, because I really don't fully understand everything about drivers, why do you say it will only work for red lasers? Isn't 330mA to a red diode, the same as 330mA to another?

Thanks for sharing!!

 

[Fretwrecker94]

I haven't played around with the drivers in these for awhile so I don't know if they have changed.

The problem is that I assume the Vf is lower than 4.5V diode needs. Red diodes have a lower Vf and can be run off of the driver. So I assume the driver puts out <3.3V

But again, I haven't tried. If someone wants to try, go for it. Although when I checked, the driver was really just an inductor and a resistor and a capacitor. Not the best driver by a long shot. But my personal one of these lasted me quite a bit before it died. And I mean a while. It was my "go to" laser for about 2 months and had heavy use. So maybe my duty cycle testing killed it or maybe the driver didn't protect it as well for a bit and it suffered.

 

[dlipford370]

Ah ok! It's the Vf thing that always screws with me, still don't fully understand it. What is forward voltage? Or if you want, instead of hijacking your thread, you can post in the one I made:

http://laserpointerforums.com/f44/driver-ma-mw-73216.html

 

[Fretwrecker94]

Ah ok! It's the Vf thing that always screws with me, still don't fully understand it. What is forward voltage? Or if you want, instead of hijacking your thread, you can post in the one I made:

http://laserpointerforums.com/f44/driver-ma-mw-73216.html

Meh, since this one's already at the top of a list, I'll just post it here.

Vf is the voltage the diode needs. IIRC, It changes as the current supplied is increased. But anyway, I think that when people talk about drivers, like the DDL Driver for example, they usually give the driver's required input voltage and then say "+Vf" so something like "3V + Vf"

So if you know the diode's Vf is 3V, you could determine you need 6V.

So in summation, as far as I know (but don't quote me), Vf is the voltage drop through a component. And in almost every case on LPF it is referring to the LD.

 

[jordan]

Thanks for all of the information, Fretwrecker! I'm looking forward to this being my first build!

I ordered some 10440 TrustFires, a charger, and a slightly more expensive housing with a heatsink + AR coated lens so I'm hoping this build will last for me

 

[Oceansoul]

Ah ok! It's the Vf thing that always screws with me, still don't fully understand it. What is forward voltage? Or if you want, instead of hijacking your thread, you can post in the one I made:

http://laserpointerforums.com/f44/driver-ma-mw-73216.html

Heh, if it makes you feel any better, you're not alone. It's something most of us have issues with. Heck, it took me longer to understand Vdrop than it did to understand phase.

Anyway.

Vdrop (voltage drop) or Vf (forward voltage) is the voltage consumed by a load as current passes through it.

Traditionally, our circuits would always have a load with a very high Vdrop. Say, for example, a light bulb.

If you have a light bulb connected to the battery, and you measured the voltage across the two terminals of the light bulb, you'd get the voltage of the battery.

Why? Because the light bulb 'consumes' all the voltage the battery supplies -- at one terminal, you've got the full battery voltage, and at the other, you've got more or less 0V after it leaves the light bulb.

Voltage drop in conventional resistive loads is determined by something called Ohm's Law.

In short, V=IR where V is voltage, I is current and R is resistance.

In other words, the voltage across the load is the product of the resistance of the load, and the current flowing through it. If the voltage increases but the resistance does not, then naturally the current through the load will increase.

That's how voltage drop works in a 'conventional' circuit with resistive loads.

Now, it gets a little confusing when you apply it to laser diodes. If you understand how a 'normal' diode works, then you'll understand that it isn't designed to consume current; rather, it's designed to pass as much current as possible in one direction only.

Now, in an ideal world, a diode would be perfectly conductive. There would be no voltage drop across it; what you put in would be exactly what you get out. Except when you reversed the direction of current flow, in which case you'd get nothing out. In reality a diode isn't perfectly conductive. Semiconductors aren't perfect, and what that means is that a tiny portion of the voltage that goes through the diode disappears.

That's what the whole 'forward voltage' affair is about. It refers to the voltage drop across the diode.

Take the common 1N4007 rectifier diode, for example. It's rated for operation up to 1kV, and it also has a voltage drop of 0.7V. What that means is that when you put a current through it, the voltage at the end would be 0.7V less than what you put in. Going back to the light-bulb analogy -- if you were to throw a voltmeter across the diode's leads, you'd read 0.7V, which is the potential difference across the diode. The thing about the 1N4007 diode is that it has a fairly stable voltage drop throughout its operating range. Put 3V through it, and you'll get 2.3V out. Put 1000V through it, and you'll get 999.3V out.

The reason why we use the term 'forward voltage' is because the voltage drop through the diode stays fairly consistent. Unlike a resistor (or light bulb) which can have a massively fluctuating voltage drop depending on the voltage being fed to it, a diode's forward voltage changes very little.

A similar deal applies to laser diodes. Not exact, but similar. Laser diodes are diodes (you don't say?), except they have the quirk of emitting coherent photons when a current flows through them.

Unlike a rectifier diode, though, a laser diode needs at least its forward voltage for optimal operation. Just like how if you put 0.5V through a 1N4007 you'll get nothing out, if you put something well below a diode's forward voltage, you won't get much out in the way of photons.

The other confusing thing that leads to laser diodes being compared to resistive loads is the change in forward voltage as the current through the diode is increased. Depending on the type of diode, this variation can be fck-all (when we're talking about 660nm diodes), up to 2V (with high-powered 405s).

For example, 12x Blu-Ray burner diodes usually sit at 4.5V, but can drop as much as 6V when running above 500mA. It depends on the diode, really.

To have a laser diode working optimally, though, you're going to need to give it its forward voltage. All of it. That's where this whole deal with boost drivers (and the FlexDrive) come in. Boost drivers can 'boost' (increase) the voltage going to the diode. That's how you can power a 12x diode (Vf of 6V) with a single 18650 battery (nominal voltage of 3.7V).

Linear drivers can't do that. They just regulate current and current only; that's why they're called 'linear' (they're linear with respects to the power supply). In fact, they actually consume some voltage themselves.

Using the ever-popular LM317 as an example, we can see (through a comparison of the minimum input voltage versus the minimum output voltage, or the maximum input voltage versus the maximum output voltage) that the LM317 has a voltage drop of 3V. That means if you put 3V into an LM317 you'll get nothing out. Put 6V into it, and you'll get 3V out.

And that's where Fretwrecker94's '3V+Vf' comes into play. The supply voltage must be able to deliver 3V (the voltage consumed by the regulator) as well as the voltage consumed by the diode.

The other thing to be aware of is that you don't need to exactly nail the Vf. If you fed a 12V lightbulb 24V, it'd burn out very quickly.

The same doesn't apply to laser diodes (within sane limits). If you hook up a diode to 110V with a constant current driver, you'll blow it up. Now, if you, say, powered it through a linear driver at 12V, you'd be absolutely fine. In fact, most linear drivers for 2xCR2-powered red lasers feed the diode up to 4V on a full charge, dropping down to 2.2 as the CR2s hit empty. That fits in nicely with the 2.3V median operating voltage of a 660nm diode.

I have a FlexMod-driven 445nm diode running at 600mA for approximately 500mW out after glass. The diode takes 4.2V, the FlexMod takes 1.5V and the rest of the 12V is 'spare', so to speak.

In the end, if you, say, are short of the Vf by 0.3V, it's not a dealbreaker. You'll still get coherent light out, at the expense of some efficiency.

And if you're using any form of boost driver (this includes most '3V' 445 and 405 drivers, as well as the popular FlexDrive or MicroBoost drivers), then you don't even need to worry about Vf, because the driver takes care of that for you.

Hope that clears up Vf for you.

 

[SciFacts4YOU]

This build is pretty sweet. Cool, yet cheap. I think I am going to try this.

 

[Gofilord]

Great build!
You gave me an idea for my next one, using this host and the stock driver!
Thanks :beer:

 

[Spyrius]

Fretwrecker, how exactly did you get the pcb and led setup out of the host without breaking anything?

 

[SciFacts4YOU]

My friend and I both tried to build this laser. After 3 attempts, all we got was 3 dead diodes, I think. My friend tried twice and failed. When I built it, it turned on real bright for a good second, then it turned dim. But it never completely went out. If I turn it on right now it will still turn on, but there will just be a dark red dot emitted from it, like less than 1mW. Do you think that my diode is fried, or do you think there is something wrong with the laser?

-SciFacts4YOU

 

[Moistenator]

This is a sick idea, I'm going to try this. Thanks.