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 Laser Pointer Forums - Discuss Laser Pointers Dummy Load & Batteries for M140?

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02-21-2014, 02:17 PM #1
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DangGucci
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Dummy Load & Batteries for M140?

Good morning everyone I will be assembling my laser today since everything comes in the mail, but I wanted to know if my homemade dummy load would function properly:

I'm using a BlitzBuckv4 driver, and a 2W 445nm M140 LD (Vf = 4.0~4.5). This being the case, I would like to set my driver to 1.8 amps (what I have seen as a relatively safe operating current for this specific diode). I already get the gist of how to go about measuring, I just want to know if I used the correct diodes and correct amount

This is the dummy: Driver Board (+) -> 1ohm 10W resistor -> 1N5404 -> 1N5404 -> 1N5404 -> 1N5404 -> Driver Board (-)

I figure using 1N5404 x4 since they drop about .85V (correct me if I'm wrong) at around 1.8 A. .85 * 4 = 3.4V. Then add the Vf of the resistor which, also after some research, seems to be 1V, so I have a total of 4.4V drop, which is within the range of the 445nm's calculated Vf. I know to measure with a DMM around the resistor.

So...will this lil rig work? Or do I need to add one more 1N5404? Also, I can't seem to find out if it matters whether I test this out with one battery or two, and what I can do for a temporary replacement of two x 18650 (S4 host with battery extension) without damaging anything or reducing power output? I've found nothing through research, and I just want to confirm the "yes" or "no." One more thing, I live in South Florida.. can I buy these batteries locally somewhere? Or is that highly inconceivable due to their nature and relatively low demand? I appreciate the patience, considering I want to make this lil' beast perfectly

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02-21-2014, 02:51 PM #2
 Class 4 Laser Join Date: Jun 2010 Location: St. Louis MO Posts: 5,482 Rep Power: 10819
DTR
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Re: Dummy Load & Batteries for M140?

Their voltage drop will be rated at a specific current and if it is .85V @ 1A then going to 1.8A will increse the drop quite a bit. For 445nm I find the red setting in this design with 4X1N4001 diodes to drop around 4.5V+ which is perfect.

02-21-2014, 03:32 PM #3
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DangGucci
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Re: Dummy Load & Batteries for M140?

Wow that's perfect, thank you so much DTR, Ill be making a stop at my local RadioShack

I already constructed the 1N5404 dummy load I previously mentioned, and since the VF of one is 1.2 @ 3Amps, I figure .85Vf for the 1.8 Amps is relatively accurate, and I feel like I read this somewhere else (confirming my suspicion). But I don't think I want to risk it; I'll go with what works best, which you have officially confirmed for me.

Is there any way to make these tests and run my laser temporarily with batteries I can purchase locally? Or should I go ahead and extract some Lithiums from one of my laptop battery packs? :P

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