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Shutter vs. Turnoff

randomlugia

randomlugia

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I want to build a safety shutter for my PHR. I know that turning the diode on and off and on and off can really put stress on a diode, and IgorT lets his go for weeks at a time because he's not always switching them on and off. So what if I just turned the shutter on and off instead of the laser? I think leaving the laser on for 5 minutes is better than turning it off and on 5 times in the space of 4 minutes. I we did this, we could leave the lasers on for 20 minutes at a time, with on switching it off once. It's better than putting your finger it front of it. ;)
 





kristopher

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Hi,

I don't really think you'd see much of a difference between on five minutes or on and off five times in five minutes.

With drivers that use modulation, the diode turns on and off 10^3 times per second (kHz-MHz range). So, I don't know what the "bad" effect would be. If you don't have enough heat sinks, then a shutter will not help you much. I was under the impression that laser diodes last longer with lower duty cycles?

Sams Laser FAQ has a pretty good discussion about this under the modulating section. Should you turn the diode off, go to just below the threshold, or some other value. I don't know if there is any consensus.

Kristopher
 
Switch

Switch

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Besides the batteries would drain faster that way. :p The only point of a shutter would be to protect from dust.
 
randomlugia

randomlugia

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Really? I thought I heard somebody on here say their's broke because they turned it on and off too much. I might make a shutter anyway, but I'll probably just buy a glow cap.  :p Thanks anyway.

200th post!!!
 
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ReaperZ

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i tried putting my finger over my 175mw greenie, to move it past a person without zapping them instead of using the shutter.. i burnt my finger! learnt pretty fast lol
 
randomlugia

randomlugia

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Nice. ;D

So wait, you're saying that doing nothing but turning the laser on and off for 5 min straight wouldn't make a difference?
 
kristopher

kristopher

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I think the problem people have is with cheap switches. When they turn the laser on and off, the switch can "spike" and kill the diode. So, if you have a good switch, I wouldn't worry about it.

K
 
pwnstar

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kristopher said:
I think the problem people have is with cheap switches.  When they turn the laser on and off,  the switch can "spike" and kill the diode.  So, if you have a good switch, I wouldn't worry about it.  

K
Click to expand...
Its not so much the "spike" because if you use a driver with a capacitor on it that will take care of any potential spikes. When the laser is off the diode is at room temperature, but when you turn it on the filament on the laser heats up very fast. That puts stress on the diode, heating the diode very fast. It is like if you are cooking with a pot but you remove the pot from a flame and put it in a sink of cold water, you can crack the pot. The temperature change is what does it.
 
randomlugia

randomlugia

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Aha, that's the answer I was looking for. ;D So this takes care of any fears I have of messing it up this way, thanks.
 
H

hydrogenman15

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kristopher said:
Hi,

I don't really think you'd see much of a difference between on five minutes or on and off five times in five minutes.

With drivers that use modulation, the diode turns on and off 10^3 times per second (kHz-MHz range). So, I don't know what the "bad" effect would be. If you don't have enough heat sinks, then a shutter will not help you much. I was under the impression that laser diodes last longer with lower duty cycles?

Sams Laser FAQ has a pretty good discussion about this under the modulating section. Should you turn the diode off, go to just below the threshold, or some other value. I don't know ifthere is any consensus.

Kristopher
Click to expand...

Yes, as Igort said. Shorter duty cycles will make your laser last for weeks even months but not hours.

Simply put: Theres no duty cycle monster, you just using the laser less and really whats the point of having a laser pointer if you always are worrying about it dying. If you put a laser in jayrobs or pretty much any sort of heat sink and ran it at its rated current it would probably last more than 5000-8000 thousand hours.

You would be able to basically set the laser down and it would run fine the battery died.


Now, about that shutter vs. Turnoff thing: It will waist battery power and is not even worth it because many of the drivers we use give the diode a "slow" start-up even though its usually under a second. ;)

--hydro15
 
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hydrogenman15

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pwnstar said:
[quote author=randomlugia link=1225761661/0#10 date=1225935046]Really? For some reason I thought rkcstr drivers instantly went from 0-100%.
Click to expand...

They do, but the rkcstr drivers are still awesome. The lava drive is the only driver I know that has the delayed start up.
http://www.laserpointerforums.com/forums/YaBB.pl?num=1209418066/0#0[/quote]


Yes, they start up WAY to fast for you to see any delay.
Flexdrives have a 1 second emission delay and after that they will have (at least to me) no delay.

--hydro15
 
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