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Bad m140 or did I do this.

thedoc8

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Bought a m140 blue diode, got the copper case that it goes in and all is well. I set the buck converter to 4.2 volts with a limit of .5 amps. Looks so cool at night. Only ran 3 times for 5 to 6 seconds at a time cause the big heat sink had not arrived. My question is. How sensitive are these, as I was standing in the dark I pulsed the power on probably 3 times, bam,bam bam and on the third bam the diode was open. This was not on purpose. So is this normal, I was running the voltage up form 2 volts until it fired around 3.?? when testing. So the question is did I do it or should it have taken the glitches. Do they need a ramp up circuit. Thanks, another small chunk out of my wallet.

Ran fine until the 3 glitches
 
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RedCowboy

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You need to use a real laser diode driver to regulate/limit current Not voltage or make a simple linear current limiter.
I like the drivers that DTR sells here
or
I use a LM338 set to 1.5a - 1.6a which means 0.8 ohms across the adj. and output pins and I use 3 li cells in series, add a 4th cell for 2 lasers in series or 8 cells in series ( 24v ) to drive 4 x m-140 in series. ** use resistors that can dissipate the wattage.

Most M-140 that you buy today are pulled from used equipment so remaining life can vary, for low hour pulls I set to 1.5-1.6a but if brand new 1.8a
 
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thedoc8

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With proper driver, will the diode take power on, power off, power on, power off in rapid succession, like my accident. Thanks
 

RedCowboy

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Yes I have switched mine on and off quickly using the SXD drivers without any issue and the SXD has a TTL input if you really want to modulate, there's directions on DTR's page here.
 
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thedoc8

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Thanks all, I just did a test with the scope on my only m140 left. Monitored the voltage and current of the buck supply set at 4.3 Volts and .5 amp. Glitched many times and the supply never exceed 4.2 and current steady at .5. The diode continues to run fine and is very cool to watch. The other diode must have been junk. Is their another good blue diode you guys would recommend

Update, checking out some spec's and seen their is a ramp time or soft start built into the drivers hear. Time to mod one of my supply's Later
 
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RedCowboy

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Lot's of blues, NDB7A75 is a favorite but divergence is not as good, now the NDB7875 is similar/same divergence and a great diode and good for 3W when driven @ 2.3 - 2.4a and that's about the over driven limit, use a good heat sink of course also there's the Osram PLTB450B which you can buy new for 20 dollars or less and the Sharp GH04C01A2G also NDB7675 is around 465nm which looks a lot brighter but they cost a bit more and are in limited supply.

Sharp 488 is a gorgeous teal color but only 100mw or so, however the NDG7475 makes a lot of green @ over 1w output, ( I know you said blue but this is a cool laser diode ) of course anything over 5mw means protecting our eyes at all times via laser safety glasses that attenuate the wavelength you're working with.

I recently ordered some of these, should arrive soon, they center @ 440nm, 5W and divergence appears to be slightly better than 7A75, I am curious how far they can be pushed, not a bad price for a Brand New 5W
 
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thedoc8

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After looking around on this site and the rush of getting things ordered, I found all the information and answers to all my questions many times over. Thanks for your reply's and being nice.
 




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