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# Running Multiple Lser Diodes. (NUBM08)

#### DashApple

##### Well-known member
What are you after

Three regulators in parallel running one string of 8 diodes at 3.5A ? or one regulator running one string of 8 diodes at 3.5A

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#### Bowler

##### New member
Both.. I want to know what the drop out voltage will be, or if they even change at all! when they are in series or parallel. That's it.

#### DashApple

##### Well-known member
Ok , Ill have a look at working it out .

Forward drop with three regulators in parallel will be abit less them one on its own for the same total currently as with three in parallel the total current is shared across them so they will drop less voltage

In theory : P

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#### Bowler

##### New member
No all I need to know are my questions.
a) What is the drop out voltage on 1 LM317 - I know its 1.5V
b) If I put LM317 in parallel does the volt drop stay the same? - I think it does
c) If I put 2 or more LM317'S in parallel does the Volt drop add up? - I am not sure

I need to know this so I can determine the correct power supply to counter the Volt drop out. Simple.

Can you see where I am coming from
Thanks

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#### DashApple

##### Well-known member
No all I need to know are my questions.
a) What is the drop out voltage on 1 LM317 - I know its 1.5V
b) If I put LM317 in parallel does the volt drop stay the same? - I think it does
c) If I put 2 or more LM317'S in parallel does the Volt drop add up? - I am not sure

I need to know this so I can determine the correct power supply to counter the Volt drop out. Simple.

Can you see where I am coming from
Thanks
a) Voltage drop of the regulator will vary with current , look at drop Vs current graph in data sheet . Only thing consistent is the 1.25V across the current set resistor .

b) Depends on what current they pass

c) Nope

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#### Bowler

##### New member
Okay thanks Dash I will look into this further on the datasheet

Cheers

#### Bowler

##### New member
Hey Guy can you help me out here please

what would the Dropout Voltage be / Head Room on Styropyro's Laser shotgun ?
Because he has 8 parallel sets with 3 Lm317's in series.

Would the Head room add up or would it just be a couple of Volts as always.

#### Cyparagon

##### Well-known member
What is the drop out voltage on 1 LM317 - I know its 1.5V

#### Bowler

##### New member
Mate what you going on about now... Check my last comment.

I have checked and it is 3V.

#### diachi

##### Well-known member
Mate what you going on about now... Check my last comment.

I have checked and it is 3V.

I'd suggest starting out with something simpler before going ahead with this project. The requirements appear to be above your current understanding. It'd be best to learn the basics and work your way up.

#### Cyparagon

##### Well-known member
the drop out voltage on 1 LM317 - I know its 1.5V
I have checked and it is 3V.

So which is it, smartass?

Spoiler: both are incorrect. What's worse, is that this has been answered several times here, and you're still wrong twice.

I've done a lot of maths and I understand this stuff as I'm a qualified electrical engineer.
As a "qualified electrical engineer", you would not ask if two regulators in parallel would have different voltages. You would immediately understand that was impossible. As I am now reasonably certain you are

A) fcking with us, or
B) lying or misrepresenting yourself or your intentions,

You can have some red bars. I've had quite enough.

#### Bowler

##### New member
Man youre an asshole, sort your life out

#### diachi

##### Well-known member
Man youre an asshole, sort your life out

He's also one of the most experienced members on this forum, someone you'd better not alienate if you'd like help. Oh wait ... too late. And for what it's worth, I've come to the same conclusion as Cyp did in his last post.

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#### Bowler

##### New member
I dont care who he is. and most experienced member lol.. he cant even answer my question about styro's circuit and what the headroom is when you have 3 lm317 in series in a parallel... all I'm looking for is help. Best member here is red; hes a star. rest of you need to sort your lves out lol, attitude is so bad.. He's a moron and so are you if you think that...

#### diachi

##### Well-known member
I dont care who he is. and most experienced member lol.. he cant even answer my question about styro's circuit and what the headroom is when you have 3 lm317 in series in a parallel... all I'm looking for is help. Best member here is red; hes a star. rest of you need to sort your lves out lol, attitude is so bad.. He's a moron and so are you if you think that...

See, your question doesn't even make sense.

what the headroom is when you have 3 lm317 in series in a parallel...
What does that even mean?

Your attitude has not only alienated Cyp and myself, but will likely also result in everyone else refusing to offer any further help. I'm certainly done offering any assistance.

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#### Bowler

##### New member
Got everything I need now,
Thanks