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two drivers in parallel to make 1.8a?

Ghostchrome

Ghostchrome

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foulmist said:
these are buck not boost drivers... you can use them to drive 445nm but for bigger currents like 1.5A you need 3x Li-batteries...

for current modifications you swap the resistor near the IC where the negative lead to the LD connects... the current is set by this formula I = 0.25 / R :beer:
Click to expand...

Awesome, thanks man. I didn't realize that these were buck drivers. duh :banghead: Thanks for the info. :beer: (+1 when I can)
 
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foulmist

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Cyparagon said:
They work perfectly on 2xlithiums for me.
Click to expand...

my batteries might not deliver enough current I guess... I use 3x16340 to power 445nm @ 1.67A I can't do it with just 2... :beer: I mean I can but at lower current :D
 
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Cyparagon

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Well, I mean it works at 7.2V from a bench supply. I tested it again, and it stays in regulation down to 6V input. I suppose it is possible that a 16340 drops to <3V under load, but if it drops that far, you probably shouldn't be using it. 2x18650 would only be slightly larger, have a much higher capacity, and would likely generate less heat in the driver.
 
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foulmist

foulmist

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Cyparagon said:
Well, I mean it works at 7.2V from a bench supply. I tested it again, and it stays in regulation down to 6V input. I suppose it is possible that a 16340 drops to <3V under load, but if it drops that far, you probably shouldn't be using it. 2x18650 would only be slightly larger, have a much higher capacity, and would likely generate less heat in the driver.
Click to expand...

well the driver doesn't get that hot but my host isn't accepting 18650... just 1, 2 or 3x18650 I have no other option :D I always test my dummy load with the power supply that I intend to use...

I sure use the bench PSU for testing but I can't put that in the host, right :D

:beer:
 
Cyparagon

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It's possible that the voltage wasn't high enough to drive the dummy load, but it's high enough to drive the laser diode. Did you check the voltage drop of the dummy load? It's not very accurate in this case, especially if you use 4 diodes like some people recommend.
 
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foulmist

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Cyparagon said:
It's possible that the voltage wasn't high enough to drive the dummy load, but it's high enough to drive the laser diode. Did you check the voltage drop of the dummy load? It's not very accurate in this case, especially if you use 4 diodes like some people recommend.
Click to expand...

no I double checked everything ... As I said I can power my laser with 1, 2 or 3 batteries.. there is very noticeable power difference when I use 2 and 3 batteries :) :beer: I can use less batteries when I want less power... and the host looks cooler with 3 anyway :D:D :beer:
 
luccax

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Cyparagon said:
Well, I tried just jacking up the current. I used a length of Chinese wire (over there, they evidently think 34 guage is acceptable for banana plug leads) in parallel with the sense resistor and got 1.75A. I measured the efficiency at 76%, which is still substantially better than a linear driver at ~60%. The temp goes higher, but I think this is still acceptable, considering it'd be in a pointer.

This is as hot as it got, and it took about 4 minutes to get this hot:

IR_0084.jpg
Click to expand...

Wich of these are you using to get 1,75A?

18V 5W Cree Circuit Board for Flashlights (16.8mm*5.5mm) - Free Shipping - DealExtreme
3.6V~16V 925mA Constant Current LED Driver Board for Cree and SSC LEDs (4-pack) - Free Shipping - DealExtreme

How did you adjust their current?

:confused:
 
foulmist

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luccax

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the resistor setting the current is that one with R22 written on it?
 
ryansoh3

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Just a warning, these cheapie buck drivers from DX are very noisy and have a lot of ripple. I got my hands on a scope a while ago, and when I measured 1.8A with a test load (with a current resistor modification) but on a scope, it was really fluctuating between 1.5A and 2.1A. It regularly spiked up to 2.4A, but only for a brief period.


The current was measured by hooking up the scope probes across the 1Ohm resistor.

So if you're driving a M140 with DX drivers, be careful!

Edit: More about current spikes and in this thread: http://laserpointerforums.com/f67/o...on-current-spikes-how-harmful-they-76523.html
 
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foulmist

foulmist

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ryansoh3 said:
Just a warning, these cheapie buck drivers from DX are very noisy and have a lot of ripple. I got my hands on a scope a while ago, and when I measured 1.8A with a test load (with a current resistor modification) but on a scope, it was really fluctuating between 1.5A and 2.1A. It regularly spiked up to 2.4A, but only for a brief period.


The current was measured by hooking up the scope probes across the 1Ohm resistor.

So if you're driving a M140 with DX drivers, be careful!

Edit: More about current spikes and in this thread: http://laserpointerforums.com/f67/o...on-current-spikes-how-harmful-they-76523.html
Click to expand...


Hmm that's sounds strange.. I have actually scoped them too and they were one of the best ripples (lowest) I have ever seen. But I can't remember at what current I did the tests.
 
ryansoh3

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foulmist said:
Hmm that's sounds strange.. I have actually scoped them too and they were one of the best ripples (lowest) I have ever seen. But I can't remember at what current I did the tests.
Click to expand...

Interesting... mine was the 2.0A driver from DX here: 5-Mode P7 LED Driver Circuit Board for Flashlight (17mm / DC 5.0~17V) - Free Shipping - DealExtreme
(now sold out)

It was rated at 2000mA, but actually delivered 2.3A or so, so I had to swap out the sense resistor with a higher value.

Do you remember what driver you used?

Cheers!
 
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