Best Diodes for RGB

[HydroSean]

So I have bought three dichroic mirrors for an RGB build I am going to make. I need some really good beam specs for the three diodes I am going for this project. I think I have some good ones narrowed down but I figured I would get some extra input as to which combination you guys would recommend. I am going to use a 445, 520, and 638.

 

[diachi]

I think I have some good ones narrowed down

Which ones would those be?

Define "really good" beam specs. My definition and yours may vary. Do you mean single mode?

How much power are you looking for...?

 

[10fenny]

Do you plan on using corrective optics? Is this for a projector build or just rgb beams?

 

[HydroSean]

Which ones would those be?

Define "really good" beam specs. My definition and yours may vary. Do you mean single mode?

How much power are you looking for...?

When I say really good beam specs, I want to use the minimum amount of corrective lens' like only a G-2 or element lens and not see any "halos" around the mixed beams. (i.e. I want to avoid things like that red "halo" around the yellow color)

I would like to have the most power possible but I have found that the more power you go into the worse your beam specs become.

I have narrowed it down for the red between the Sharp GH0631IA2G(single mode) and the Oclaro HL63193MG(multi mode). I'm pretty sure the Sharp is single mode and the Oclaro is a line beam spot. My question is do you think I can just make a circular tube to put in front of the diode+lens to cut it off and make it a circle and still be more powerful than the Sharp?

For the green I am pretty much set on getting the OSRAM PL520B, unless you think there is a better 520nm tight beamspot diode out there over 100mW.

For the blue I have narrowed it down between the PLT5 450B(single mode) and the PLTB450B(multi mode) from OSRAM. My questions are the same as for the red diodes. Would it make sense to put a circular tube in front of the PLTB450B to cut it off to more of a point and still have more power than the PLT5 450B?

Do you plan on using corrective optics? Is this for a projector build or just rgb beams?

I would like to use as little corrective lens' as possible other than the stock G-2 or element lens, I will be getting those for each of the diodes. It is going to be bench tested and then put into a handheld laser for pointing.

 

[diachi]

I would like to have the most power possible but I have found that the more power you go into the worse your beam specs become.

That is generally correct, at least for diode lasers.

My question is do you think I can just make a circular tube to put in front of the diode+lens to cut it off and make it a circle and still be more powerful than the Sharp?

It doesn't work like that, you can't just mask a beam and get better beam specs. You need to correct it.

I don't have many suggestions on which diodes will go well together. 10fenny will likely be able to offer more assistance.

 

[CurtisOliver]

High powered RGB's have less desirable beam specs due to the diodes being multimode and the specs differing for each diode. For the cleanest rgb you need single mode lasers at a lower power. If you want high power, then you need to use beam correction. If you go down the DPSS route, expect a large bill however, but the specs will be better.

 

[HydroSean]

Okay yeah I think I'm set on getting all three to be single mode. So these are the ones I am going to get;

Sharp GH0631IA2G
OSRAM PL520B
PLT5 450B

sound good?

Also this maybe sound like a noob question but in order to adjust the output power of each diode would it make sense to put a potentiometer between the battery and driver and have the driver set to the max current? (each diode has its own independent driver and battery)

 

[CurtisOliver]

All three options seem good. You want to do some research into the beam diameter and divergence, but all are good diodes. Don't laser drivers usually have a potentiometer on them already? :thinking: Especially if you opt for one that specifically states 'adjustable current'.

 

[HydroSean]

All three options seem good. You want to do some research into the beam diameter and divergence, but all are good diodes. Don't laser drivers usually have a potentiometer on them already? :thinking: Especially if you opt for one that specifically states 'adjustable current'.

Yeah the nano drivers that DTR puts on them are adjustable. The problem is they are adjusted with this tiny screw which doesn't make it very easy to adjust when I put it into a host. My end goal is to put it in a host and have three knobs which I adjust to change the power of each diode.

 

[CurtisOliver]

Yes they are small, if you want to be able to keep adjusting then honestly I don't know myself. I'm no good with electronics. I just wire up go usually.
I'm sure Diachi or someone else will know. I would probably go to the hassle of making a custom adapter to turn the screw.

 

[Chrisbee]

The only drivers that I know of right now where you can add an external trim pot to, is those BlackBuck 8M drivers. Unfortunately, they are for high power diodes, and have a range of like 1-8A.

 

[HydroSean]

Yeah which is why I was asking if I should put the pots between the batteries and drivers... I don't know if that will work because the drivers are that buck/boost kind which I vaguely understand, won't they buck the current up even when the battery voltage is weakened by the pot?

 

[Chrisbee]

I don't think that'll work. As far as I know, more voltage = more heat, and less voltage = voltage cut.
I would just get a jeweler's screwdriver and call it good. If you strategically mount the drivers, you can access the trim pots when needed. That's what I did for my lumia build that I'm working on.

 

[10fenny]

Lpc 826 is a great red diode as well. As for adjustment you will need need analog modulated drivers which you don't really see in handhelds. If your use the pot on our handheld drivers you run the risk of current spikes and blowing the diode. You might want to look into building small analog drivers

 

[HydroSean]

An analog driver like an LM317?

 

[diachi]

An analog driver like an LM317?

No, that's a linear regulator.

An analogue driver is a "constant" current driver that takes a 0-5V analogue signal and uses it to modulate the drive current to the diode, with 0V being just below diode threshold and 5V being full current.

You can make an analogue driver from an LM317, but you need some more components, a couple Op-Amps for a start.

You'll want an analogue driver so that you can change the colours on the fly. :beer:

The BlackBuck 8A has this functionality. Or at least to some level - you can control drive current with an external pot on that. You never want to use the current set pot to set output on the fly.