Running Multiple Lser Diodes. (NUBM08)

[Bowler]

Tbh, that's exactly what I plan to use it for. Cutting up objects and letting them melt. MY MAIN question is how would I get this to perform efficiently and safely for its own health. Which I want to wire in parallel. I know people say it's not, but looking at it I think their both the same. The only thing that changes is the current and voltage. As long as you know how Parallel and series circuit works ure fine, just depends on the application which suits best. and any new suggestion would be taken into account and thanked for in advance.

I can however thank you guys for your knowledge; especially red for helping me out with my maths and you guys sharing your knowledge I would love to know how you guys know so much on this? Is this a hobby for you its job?

 

[RedCowboy]

I would probably use 1 regulator for the center 4 diodes in series and one for the outer 4 diodes in series and use 6 or 7 26650 li-ion cells in series for each set unless I could find a good 25 volt hobby pack.

I would run the 08 diodes at 3.75 to 4.0 amps, the block will need a good heat sink and being able to run just the center 4 could be useful to extend runtime, I might even push out the outer 4 and just keep the center 4 anyway.

Have you used any of these diodes before? You must protect your eyes, at arms length you can go blind for a moments mistake, do you have laser safety glasses for 450nm?

If you need good glasses at a good price these are what many of us use >>> http://www.survivallaserusa.com/Safety_Goggles/cat1667093_1527285.aspx

 

[AngelG]

...............................................................
3) Linear regulators are actually quite efficient at higher voltages. 4V drop on a 40V load for example is 91%, which is more than most switchmode regulators.
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1. Yes, I admit that I haven't seen them in oscilloscope, what interesting could have missed ? Bad current limiting ? 50 mA ripples at 4A load ?
2. This 4V drop is nearly impossibly to achieve, because your 41V Li-Ion battery pack (scaled from 4.1) will be discharged at 30V.
So you have to have at least 13V drop to get stable current in the Vin range (41..31V) (given the Vout is 27V, which is the ideal case).
At 4A current, this will lead to UI = 52W pure waste of energy at 41V going down to 16W at 31V.
And with synchronous rectified SMPS, you can get over 95% efficiency. I'm talking about similar boards to this one: LTC3780 Automatic Constant Voltage/Current Step Up Down @ eBay

 

[diachi]

1. Yes, I haven't seen them in oscilloscope, what interesting could have missed ?
2. 4V drop is nearly impossibly to achieve, because your 41V Li-Ion battery pack (scaled from 4.1) will be discharged at 30V.
So you have to have 13V drop to get stable current in the Vin range (41..30V) (given the Vout is 27V, which is the ideal case).
At 4A current, this will lead to UI = 52W pure waste of energy at 41V, down to 16W at 31V.

1. Voltage spikes on start, noise/spikes while running.

2. Not entirely sure what you're on about, but Cyp is correct. Running at higher input and output voltages voltages but with the same voltage drop results in better efficiency.

40VIN @ 4A/36VOUT @ 4A = 160W/144W = 90% efficient.

10VIN @ 4A/6VOUT @4A = 40W/24W = 60% efficient.

 

[AngelG]

O.K., I surrender. Viva the linear PSUs. Everybody's free to think and make it his way.

 

[Bowler]

Okay thanks red
I'll have a look into this circuit with the lm338t was it?

And yea I am very aware ! I will check out your link too

 

[Bowler]

Hi Red,

In regards to you comment, what Regulator would you put in series with the LD?

The problem I have with Series is that they require more Voltage (If i was to use all 8), with voltage comes a bigger battery and a bigger price. With parallel you can get a fairly small battery with high current and a voltage you can work with. What do you think about this?

Ideally I would want a power supply that I could just run from my mains. that would be a good permanent solution to this. You guys have any suggestions?

In addition to this, Could a possible solution just be a variable work bench power Supply?

Cheers

 

[diachi]

Hi Red,

In regards to you comment, what Regulator would you put in series with the LD?

The problem I have with Series is that they require more Voltage (If i was to use all 8), with voltage comes a bigger battery and a bigger price. With parallel you can get a fairly small battery with high current and a voltage you can work with. What do you think about this?

Ideally I would want a power supply that I could just run from my mains. that would be a good permanent solution to this. You guys have any suggestions?

In addition to this, Could a possible solution just be a variable work bench power Supply?

Cheers

What about 2x LM338, one powering 4 LDs in series each. That'd work. You could use a 24V supply voltage for that if you want to power from mains. Mains->24V switch mode->Regulator.

Do not recommend a variable bench PSU, fine for testing, not a permanent solution.

I'm surprised we're even still discussing this really...

 

[Bowler]

we're still talking about this because that's what life is all about. HELPING each other, its apart of kindness and love

 

[Cyparagon]

I did see 36v as the maximum differential

Short example of how that doesn't apply here:
pin IN: 44V
pin OUT: 41.25V
pin ADJ: 40V

The highest differential is 4V in CC mode.

I read the 138/338 could handle several 100's of volts

Calling bullshit.

1. Yes, I admit that I haven't seen them in oscilloscope, what interesting could have missed ?

I'm not going to pretend I've tested all varieties, but I've seen enough bad ones to adopt the rule "garbage until proven otherwise". They're generally okay for battery charging, but not lasers, and especially not 4-figure lasers.

Could a possible solution just be a variable work bench power Supply?

Certainly. That's rather large and expensive, but it would work.

I have to reiterate, this device will NOT work for cutting things. It will just set them on fire.

 

[RedCowboy]

The LM138 series of adjustable 3-terminal positive voltage regulators is capable of supplying in excess of 5A over a 1.2V to 32V output range. They are exceptionally easy to use and require only 2 resistors to set the output voltage. Careful circuit design has resulted in outstanding load and line regulation— comparable to many commercial power supplies. The LM138 family is supplied in a standard 3-lead transistor package. A unique feature of the LM138 family is time-dependent current limiting. The current limit circuitry allows peak currents of up to 12A to be drawn from the regulator for short periods of time. This allows the LM138 to be used with heavy transient loads and speeds start-up under full-load conditions. Under sustained loading conditions, the current limit decreases to a safe value protecting the regulator. Also included on the chip are thermal overload protection and safe area protection for the power transistor. Overload protection remains functional even if the adjustment pin is accidentally disconnected. Normally, no capacitors are needed unless the device is situated more than 6 inches from the input filter capacitors in which case an input bypass is needed. An output capacitor can be added to improve transient response, while bypassing the adjustment pin will increase the regulator’s ripple rejection.
Besides replacing fixed regulators or discrete designs, the LM138 is useful in a wide variety of other applications. Since the regulator is “floating” and sees only the input-to-output differential voltage, supplies of several hundred volts can be regulated as long as the maximum input to output differential is not exceeded, i.e., do not short-circuit output to ground. The part numbers in the LM138 series which have a K suffix are packaged in a standard Steel TO-3 package, while those with a T suffix are packaged in a TO-220 plastic package. The LM138 is rated for −55˚C ≤ TJ ≤ +150˚C, and the LM338 is rated for 0˚C ≤ TJ ≤ +125˚C.
Features n Guaranteed 7A peak output current n Guaranteed 5A output current n Adjustable output down to 1.2V n Guaranteed thermal regulation n Current limit constant with temperature n P+ Product Enhancement tested n Output is short-circuit protected
Applications n Adjustable power supplies n Constant current regulators n Battery chargers


http://diyaudioprojects.com/Technic...M338-5-Amp-Adjustable-Regulator-Datasheet.pdf

 

[Bowler]

Hi all,
With that all being said

Question A) And what resistor would I need to put on the LM138 (Powering all 8 Please) I can find the calculator it... i.e. 1.25V / 0.36 Ohms = 3.472A (Max is 3.5)

Question B) What would the drop out voltage be on the Parallel Circuit using 3 Lm317's to each LD ? it wouldn't be 1.5V x 3 = 4.5 would it. (I know it wouldn't because they're in series, just bringing you up to speed; But) what about them being in parallel with each other. It wouldn't be 1.5 x 8 = 12V would it? Can you please explain why because I am curious to this!

Just firing away my questions for you all.

Thanks.

 

[Cyparagon]

Bowler, please read the datasheets. The Datasheets on these components will answer most of your questions.

For your "Question B)", I have a feeling you're imagining something totally different than we are. Since you're being vague and jumping between design ideas CONSTANTLY, we're going to end up guessing your message incorrectly.

Please draw a schematic.

supplies of several hundred volts can be regulated as long as the maximum input to output differential is not exceeded

That's not what you said. You said it "could handle several 100's of volts" which is false.

I can build a device out of multiple 1N4007 diodes to block 50kV. I would be wrong, however, to say the 1N4007 "can handle tens of thousands of volts"

 

[Bowler]

Hi Cyparagon.

My question is Stryo's laser 08 one, remember that one? He wired that in parallel with 3 lm317's for each LD. I am asking what the voltage dropout would be. (Sorry if I wasn't clear, I was up late). Because he wired it to 8LD, would the dropout voltage be 1.5V x 8 ? (Are you following) and how do I determine the drop out voltage. I am struggling to understand the graph to be honest, help would be much appreciated!

And as Diachi and Red mentioned I think LM338 would be a good candidate. however I need to know what the dropout voltage would be, or how to determine this so I can select a correct power source, where I decide to wire this up in Series or Parallel.

Hope you can help,

Cheers

 

[diachi]

Hi Cyparagon.

My question is Stryo's laser 08 one, remember that one? He wired that in parallel with 3 lm317's for each LD. I am asking what the voltage dropout would be. (Sorry if I wasn't clear, I was up late). Because he wired it to 8LD, would the dropout voltage be 1.5V x 8 ? (Are you following) and how do I determine the drop out voltage. I am struggling to understand the graph to be honest, help would be much appreciated!

And as Diachi and Red mentioned I think LM338 would be a good candidate. however I need to know what the dropout voltage would be, or how to determine this so I can select a correct power source, where I decide to wire this up in Series or Parallel.

Hope you can help,

Cheers

As Cyp said, that information is all in the datasheets.

Placing several regulators in parallel shouldn't change those values, all that does is spread the load across all regulators, allowing you to provide more current.

 

[Bowler]

Yea I know that's what he said, but I couldn't see anything...

And okay cool, what about when you run them in series? Say I have 3 lm317, it won't be a dropout voltage of 1.5 x 3 for example.

Cheers