The 445 General Zod Quad

[CDBEAM]

A new project is being hatched in the Terrawatt Labs !!! Since ALL projects need a good name !!! This one will be identified as the “ General Zod Quad “…A 445nm Quad unit using bits mainly from Dave at Laser Show Parts. I plan on the final home for this unit to be a stand alone, one (1) color, mainly beam show projector. I want to use the very nice Brass mounts from Dave, P1t8ull’s prisms and PBS…Lava’s FlexmountP3 and a ½ waveplate GB…also from Dave. Collimination lenses are from O-like and four (4) A130 445nm diodes from Laserbee. Knife edge mirrors/mounts also from Dave.
The goal is to utilize minimal machining and existing prefab components when possible. A detail not yet fully worked out is how to mount the waveplate optic ?? For now….I want to use another LD mount…with the waveplate set with epoxy to a M9 threaded tube. This tube/WP unit to then be screwed into the LD mount. Once the optimal radial position is determined…the tube/M9 unit can then to be locked in place with a set screw.
As far as thermal management….I would use a hefty slab of Copper as a base…approx 15mm thick….with a cooling fan to remove internal heat from the diode mounts. Perhaps I will need TEC to dissipate approx 20 Watts of heat?? Dunno. To start with….I will mount a small temp meter to the base….and see what happens @ full PO over time. We will see !!!
As far as wiring up four (4) diodes…..I seem to see multiple LD’s wired up in series ??? As far as using resistors to “ balance “ the current load ??? Perhaps some PL’er could further explain this ???? These four (4) diodes will NOT be electrically isolated. Wire them in parallel ????? I thought in series ?
Anyway…see the attached drawing.
Happy New Year…
CDBEAM and Terrawatt

[dnar]

Looks good and sound. Pretty much what I did for my quad red, although by staggering the LD heights I managed to knife edge a pair stacked vertically.

I paralleled my 4 x LOC with 1ohm resistors to balance, although you can wire your 4 x 445's in series as they are case isolated, much easier. Just make sure you provide the P3 with 24V.

[CDBEAM]

Thanx !!! Yea....I forgot the 445's are case isolated !!!! So ...they will be wired in series !!

Terrawatt wanstah know...." But will 4.8 watts cut thru a Milk Bone ??????? "

CDBEAM

[LaNeK779]

i suggest you don't measure the temp of the base plate, but place the sensor as close to the diodes as possible

maybe by the time the baseplate hits 25 degrees, the diodes will be well over operational specs

[dnar]

i suggest you don't measure the temp of the base plate, but place the sensor as close to the diodes as possible

maybe by the time the baseplate hits 25 degrees, the diodes will be well over operational specs

Sensor placement really comes down to the control algorithm employed. With proportional only, you want the sensor as close to the TEC as possible. PID is more forgiving and generally the sensor is placed near the component to be cooled. This is all about thermal time constants.

I think generally we are all using mounts and base plates that have sufficiently low thermal resistance that temperature differential between base and diode is fairly minimal.

[LaNeK779]

that's good to know wayne, thanks. so to be safe at all times, try and stack the sensor the diode and the tec as close as possible

in my blue and red modules (if i ever finish them) they will all be within a 1,5cm radius

[dnar]

that's good to know wayne, thanks. so to be safe at all times, try and stack the sensor the diode and the tec as close as possible

in my blue and red modules (if i ever finish them) they will all be within a 1,5cm radius

Yes, you can do this. My point is this, once you mount a 445nm in a block or housing, and then mount the housing to an ali plate, the temperature rise is not that fast in my experience. For me, I don't even see the need for a TEC, based on my results at CW. Consider that when running a show with modulation, the duty cycle is reduced significantly also.

In general I think some are over-paranoid about cooling the 445 diode. You need to understand thermal dynamics too, with a heat source (LD) mounted in a relatively small housing mounted to a larger thermal mass (base plate) the heat will be transferred from the mount to the base plate. The small mount will not be much hotter than the larger base plate.

I stay away from TEC's unless absolutely necessary, because for every watt of heat you remove from the diode, you have 2 watts of heat (or more) to get rid of, so essentially you create more heat to move a smaller amount of heat. I am not saying TEC's do not have their place, just stating I feel they are not necessary for the purpose of "long life" or protection of 445 diodes. Wavelength or optics stability is another argument of course.

[CDBEAM]

Good comments/observations !! On my " Copper is Proper " Test Bed assembly...the temp probe is inserted directly into the Copper block where the LD is mounted....as close to the LD as possible !! In the Zod Quad...the Brass LD holder will flow heat into the massive Copper base. Thermal Equilibrium will be served...and the Delta T will be minimal....but there will be some Delta T...and unless you mounted the probe in direct contact to the LD case....there will always be some difference !
I will mount the probe into one of the brass holders.....one less hole to drill into Copper too !!....which is a PITA to drill and tap !!!

Bottom line: " Close enough for Jazz " especially with modulation considered. ANY other 445nm Quad builders having issues with heat managment ????? Your solutions ???

But...Will 4.8 Watts cut thru a MilkBone ???

CDBEAM

[dnar]

But...Will 4.8 Watts cut thru a MilkBone ???

CDBEAM

My guess? Yes it will!

[Robin]

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