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(SOLVED) I... I'm Kinda Retarded

gazer101

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Also, a totally unrelated problem, how do I calculate the right resistor value to use across the Vout and Adj pins to get my desired 1.8A. I want to remove the potentiometer and make it so it uses only one resistor instead
 



Lifetime17

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I need <20mm diameter that can output 4-6V at 1.8A (powering a 1W green LD). It can be up to 5mm tall

EDIT: I want to build the circuit myself using linear regulators, so ideally the design shouldn't require too too many parts

Hi,
You said you need a 20mm round driver, so why not purchase a 17mm round driver and use a 17mm to 20mm brass ring to hold the 17mm round driver. instead of trying to fix the cheesy Chinese driver. And you can get your driver fro Survival Lasers.
Also I have the 17mm to 20mm brass driver rings . Problem solved and you can get on with your build/repair.
Rich:)
 

Cyparagon

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2 problems with your test. 6 of those diodes in series is going to be about 5.5V at this current. If that's a 1ohm shunt, that's another 1.8V. So I'm estimating you're driving a 7.3V load in an attempt to emulate a 4.5V load. Also, The lm317 current source needs almost 4V of overhead to function reliably. Add in the internal resistance of the lithium cells, and you really need to have three in series for this topology to work. That's why no one uses this for high power, and I'm confused why it's still suggested. There are also several sticky threads on this, and other similar drivers.

As for resistor calculations, it's just ohm's law. If that's too hard, there are lm317 current calculators like this one. At least put some effort into google.
 

Lifetime17

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Hi Gazer,
You see folks like Cyp are willing to share ..
Rich:)
 

gazer101

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2 problems with your test. 6 of those diodes in series is going to be about 5.5V at this current. If that's a 1ohm shunt, that's another 1.8V. So I'm estimating you're driving a 7.3V load in an attempt to emulate a 4.5V load. Also, The lm317 current source needs almost 4V of overhead to function reliably. Add in the internal resistance of the lithium cells, and you really need to have three in series for this topology to work. That's why no one uses this for high power, and I'm confused why it's still suggested. There are also several sticky threads on this, and other similar drivers.

As for resistor calculations, it's just ohm's law. If that's too hard, there are lm317 current calculators like this one. At least put some effort into google.
Keep in mind that lord Styro used linear regulators in his 100W handheld. Thanks for the input Cyp! I will take a stroll thru my local FPV store to see if I can find some kind of weirdly shaped LiPo I could use for the high voltage input. Is there any other topology that a newb like me could cheaply deploy for driving 1.8A?

Addendum: Also, as the name of this thread suggests, I'm kinda retarded. So before I test this on a $70+ diode (NUGM03) I just wanted to sanity check this; I have a driver powered by 7.4V powering 4 diodes and 1 ohm resistor in series, when I electrify it with 0.8A I read 5.3V across the entire dummy load. But when I remove the dummy load and measure the output + and - of the driver, I get 7.2V. Is that normal? Is the voltage coming out of my driver too high (datasheet mentions acceptable input range of 4 to 6V)?

Sorry for my rarted questions XD
 
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Encap

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Aight folks, I got the thing to work but it needs a pretty high input voltage in order to output enough voltage. Idk what I'm doing really, so is there some way for me to make it so that the circuit boosts the 3.7V from a regular battery up to the correct output voltage? Or if not is there any kind of compact battery that outputs high voltage (12V+ with less than 18mm diameter and 35mm height).
View attachment 69089View attachment 69090

I looked at this SL driver (https://www.survivallaser.com/Survival_Laser_Fixed_Current_Driver/p556088_7425633.aspx), but the darn thing needs 2 batteries (4.2V+) to run since it has no boost circuit!

Long story short, do you know of any circular 1.8A laser drivers that can operate (without making too much heat) off of just one LiIon battery?
Please help me out here :)

Apparently you did not read the description of the Survival Laser driver you gave a link to. It clearly states " capable of delivering from 220mA to as much as 1.8A of regulated current at a recommended input voltage of 4.2 to 8.4 volts, meaning either one or two batteries. A standard 3.7V li ion battery is 100% charged at 4.2V---so SL means one or two standard batteries eg. 1 x 18650 or 2X 15340 or 18350'.
Email Gary at Survival ask and confirm--problem solved

DTR supplies NUMB03 diode in 12mm module housings complete with driver inside the housing, in case you didn't understand---all of his drivers listed for an NUBM03 being on ly 10mm X 16mm X 3.5mm can fit inside any of his offered holliow back modules. If you are using a diode in a module you are good to go--if not using any module then maybe his drivers would not fit in your application.
 
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gazer101

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Kk, I'm doing some final testing but so far my solution seems to have worked. I might post a build thread later on. Thanks everyone for the help
 




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