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The Green Gargoyle 10.08 W @ 520nm

RedCowboy

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I wouldn't try just 1 pot for all 6 drivers but a 6 gang pot would work, here's one that's 13mm but should be able to find a micro somewhere, mouser would have it but can likely get for cheaper elsewhere.


 



CDBEAM777

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Wow...6 pots in 1....13mm x 35mm ( Body )...small....inexpensive....Good solution !! Thanx RC !!!

Another possibility...the Wossee L5000TG driver. I have used this unit...PWM used to vary current output …. small....less $$ than the 8A supports up to 4.9A....fine for the NDG7475... Sent Wossee a email asking for assistance !! He has been so very helpful in the past !! He has put up with a great deal of my....er...ah....issues !! Near drove him crazy on the Supercar build !!!

Either way....another loose thread tied up !! We continue the journey !!

CDBeam
 

logsquared

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Looks like the mod input on the 8A is just a voltage input. One pot should work fine to drive multiple drivers. Depending on the input impedance of the drivers a lower value pot might be needed.

Depending on the voltage of the battery pack 2 or 3 diodes in series per driver might be more efficient.
 

RedCowboy

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You can't drive 3 x 7475 LD's in series with the BB8 as the max supply voltage is 12 but you could drive them in parallel, however one could draw more current than the others so parallel is not recommended.

You could control all 6 drivers with a single PWM signal but it needs to be limited to 5v







The output current can be controlled by an external signal, analog or PWM. The maximum modulation voltage should not exceed 5 volts. If your source has a different signal level, then you need to convert its level to allowable values. (for example, most Arduino-based controllers are fully compatible). The external potentiometer (1...10K) can be used as a control signal (modulation) source - the driver has a special reference output of 5 volts. To avoid damagethe driver, do not shorting this output to any circuit.

 
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Alaskan

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Bob, could we use those series-parallel battery holders so we can easily swap out batteries? Those holders can either produce 8.4 VDC, or be modified to place all four batteries in parallel in each pack and have contact terminals on each end so if two holders are placed in a tube, the voltage remains the same at 4.2 VDC when fully charged (if using Li-ion batteries).

Maybe you want the higher voltage? Not sure, but reading the last posts, appears so. If we are using eight 18650 batteries and have a control to turn the fan velocity up or down, makes sense to me to draw current from all eight batteries, that way if the fan is not pulling so much power at a slower speed (if we don't end up needing it running full speed), we would have more capacity for the laser diodes.
 

CDBEAM777

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We could go with the carriage holders...sure....or... I have figured out a simple method to derive 15 VDC from one side ( 4 cells in series )…..and 7.5 VDC from the other side ( 4 cells in parallel ) by modifying two Skyray hosts. Easy....so...the fan gets 15 VDC....and the drivers are supplied 7.5 VDC.
Gotta study this more....and adjust my antenna !!!!!
 

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Alaskan

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This is very unorthodox but in this configuration (if limited to 8 batteries total) you can then parallel more of the batteries together for the diodes. This will only help conserve the diode battery capacity if the fan is using 1/3 or less of the total current the diodes draw over a period of time. If the fan draw it exceeds that amount, the cooling fan batteries which are added to boost to 15 V will drain before the diode batteries and then no cooling if that happens.



Imagine each power supply to be Li-ion batteries in series, same concept. Power supply 1 can be two batteries in series, power supply 2 three sets of two batteries in series but paralleled together (six batteries) to increase total AH capacity to the diode drivers.

I am offering this as food for further out of the box thinking on this, maybe you can come up with something else after looking at this or just decide it isn't worth it and use two sets of four batteries as the fan probably draws too much current to do this.
 
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CDBEAM777

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OK...I have modified a single Skyray tube before to deliver 7.5 VDC to the driver.... I have a simple plan on how to couple Two (2) host battery tubes together....so....this will yield room for Eight (8) 18650 Li{o cells.

The cells will be arranged per drawing GG Battery wiring 1. In the Parallel drawing.... secondary + wire will be run back to the connection end.
This is really simple. Very inexpensive....and I have done this B4.

In the end...I want to deliver 15 VDC to the fan....which it is designed for....and 7.5 VDC to the drivers...Likely the Wossee L5000TG driver...and they are designed for a supply range of 7~12 VDC....

In the attached pic....you see only one Skyray tube....I will use two....coupled (Screwed) together....simple and secure !!

CDBeam
 

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CDBEAM777

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Consulting with Wossee now....we may have to go to this.....No Problem....but handle will be extended by 71.76mm.....just the way it may be !!

We are after all.....firing up Six laser's and producing the brightest beam yet seen in a HH unit !! So it goes !

If this ends up our arrangement....well....both sides of the tubes would be set up the same !!!....and we would get longer run time on both the fan and LD's !!!

CDBeam
 

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RedCowboy

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Yes, 3 cells in series is how I like to go even with single 44's because as batteries discharge they can sag below cutoff with only 2 cells in series and a higher Vin means less current the cells have to supply to the drivers.

With 6x7475's you need 2.3a @ 5.0v to the diode which is 11.5w so if the driver is 95% efficient we will round input to 12.25w x 6 = 73.5w from your cells which if 7.4v means right at 10 amps but if 11.25v then 6.5a from your battery pack.
If 6x18650 in series parallel ( 2 strings of 3 cells ) then 3.25a from each cell for the drivers/diodes.

How much current will your fan draw because as it stands you are good for the 6 lasers with 6 cells but if the fan draws a lot.........

----edit----

If you are thinking about using this 50mm fan then know it takes 40 amps at 12v which you do not have, not even close except for maybe 10 seconds, you need a much smaller fan or a lot more battery.

I think you can get by with a lot less fan velocity as that fan will sound like a hair dryer on roids, the 50-70mm blade dia. is fine but the hyper velocity costs a lot of power and I don't think it's going to make that much of a difference vs. a decent normal fan, the hobby fan is meant to fly a model airplane and needs it's own dedicated battery pack which will sag under load, you could run it at lower speed of course as 40a is takeoff/full tilt but I don't know what it will draw, you could test it and see.

If using that hobby style fan then maybe 2 x 3cell hobby packs, one for the lasers/drivers ( 6.5a ) and one for the fan ( 10a ) +++ ?

----edit----

If you use a regular brushless style fan and the duty cycle ends up being several minutes then the fan will help cool down faster between runs, but the DLP projectors use normal fans and have continuous duty and they do carry away as much waste heat, we don't know the surface area per watt of aluminum used but you have seen the heat sinks from projectors so with the internal fins maybe a normal fan will do the trick.
 
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CDBEAM777

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WOW....A great amount.... of great info !!! THANX !!!

The bottom line....we (I) just do not know how much waste heat the 6 x NDG7475 will generate !!! I think I need to step back....and come up with a more controlled plan !!

Optically, I think we are on solid ground. Bouncing beams is really the easy part. SO.....Perhaps I should construct One (1) Optical/LD section....fire it up with Six (6) independent drivers.

I am a very big fan of our overall geometry....using a rear handle with LiPo cells populating the inside !!

I think we have a good plan for evacuating heat from the centre of the hex bar.....so.....really......if I set up a test unit....I would machine out the centre….and install the finned heat sinks.

SO then....maybe I start with a single...or double 80mm fan....like the Noctua NF-A8....and see what happens !!! Monitor the Hex Bar temp to see what we get. I have been concerned with fan noise and power consumption for some time. Yep.....the FMS site notes a 40A draw....and this unit will not operate quietly....even if it is balanced near perfect !

SO....unfortunately....or....maybe fortunately....we unfold this build....based upon empirical data....design as we go....so to speak.

I also, based upon observing a single NDG7475 driven at 1.4A., ...do not see that much heat generated within a 5min run ….and this is just with passive CU Heat sink.

SO....I am now of the opinion....that is how to move ahead..... Slowly.

Your thoughts ???? I continue to strongly thank all those offering very helpful suggestions !!! We all …."have our hands on the Tiller".... trying to not crash into the rocks !!!

CDBeam
 

RedCowboy

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If you drive your 7475's @ 2.3a they will take 4.9v which is 11.27w and the light output is about 1.27w maybe a bit more but we are rounding to 10watts of waste heat per laser so 60 watts of waste heat for all 6. Drivers are 95% efficient so not that much heat there.

A nubm44 driven @ 4.5a draws 4.5v which is 20.25w and outputs 7.25w of light so 13watts of waste heat.
A ndb7875 driven @ 2.4a draws 4.9v which is 11.76w and outputs 3w of light so 8.75watts of waste heat.

So 6 x 7475's will generate about the waste heat of 4 x nubm44's or 7 x 7875's ...............it's quite a bit really, my 3 x 7875 unit had a 2.5 x 2.5 inch head ( round stock aluminum ) and it got hot in about 2 minutes but the battery tube didn't carry heat as well as a custom build, so without cooling you would want to go heavy on the heat sink and runtime would be in the 120 seconds range est.....but active cooling should help a lot, the v1 projector had 7x44's and v2 had 8x44's and they were air cooled but were not overdriven.......still air cooling works and if the fan and internal fins means a 10 min duty cycle rather than 2 min with a smaller fan then that's not bad........could go with the 50mm hobby fan and give it it's own battery ( A 3rd holder with 4 cells in series parallel ) as you wont want to run it at 12v/40a but maybe 7v/10a and maybe test this 1st, but it will run at lower power as it's made to throttle up and down.
 

Alaskan

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I like the idea of a monster fan, but 40 amps, holy flying cows, that is a lot. I don't think we need that much fan, I bet a fan drawing 5-10 amps is enough, as long as it can handle back pressures. I am also a big fan of easily removable batteries, what if I am out somewhere signalling the mother ship and run this thing down, I can't always just plug in to recharge it and if I did, it would take too long.
 

CDBEAM777

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OK......SO...We keep the twelve (12) 18650 LiPo arrangement….and evolve to using Two (2) stacked Noctua 80 mm fans. From reviews I have read... these Noctua Fans are the best for Quality, Air flow and Low noise. I am suggesting that two (2) fans should be stacked...We have the room and need to maximize our Static Pressure....yet not consume a huge amount of current. The fans will be speed controlled/PWM.

Using Two of these fans is what I would like to test.

I am not decided whether to test One (1) NDG7475....or test all Six (6) NDG7475 mounted to the Hex Bar with the finned heat sink installed....or ...maybe a group of three (3) NDG7475 with one (1) fan.

For the test...I will monitor the LD mount temp rise.

Ok...See yet the latest tentative arrangement….. V 3.03

See below for possible fan ( I will have to modify the case to bevel the corners @ 14mm )


We must do some tests before we finalize the GG design ! This is the only way I see to verify the theoretical predictions.

Added; Wossee suggests we use the Blackbuck 8A drivers as they add less heat. He also notes than a single Pot can be used to modulate all six (6) drivers....simultaneously.

CDBeam
 

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RedCowboy

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Sweet, I hoped that you could control them all with 1 pot but I wasn't sure, that's some good news and I think the revised fans are also the right way to go, look forward to seeing this beast beaming. :p :love:
 

paul1598419

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Hey, Bob. Where are you getting those 5000 mAh 18650s from? Is that a real thing of just more Chinese optimism?
 




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