Old 06-24-2014, 06:05 AM #1
IsaacT's Avatar
Class 4 Laser
 
Join Date: Aug 2010
Location: Austin, TX
Posts: 5,901
Rep Power: 748
IsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond repute
IsaacT IsaacT is offline
Class 4 Laser
IsaacT's Avatar
 
Join Date: Aug 2010
Location: Austin, TX
Posts: 5,901
Rep Power: 748
IsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond reputeIsaacT has a reputation beyond repute
Default Power Fluctuations - Attributable to Which?

I had always thought of the diode as being the only factor in power fluctuations. How hard it was being driven, how much heat building up, etc all causing it to vary wildly. A number of lasers I have built in the past have had a habit of starting high and then dropping quickly.


But it occurs to me that possibly the driver has more to do with the fluctuations than the diode itself. Could it be that heat being dissipated by the chips on the driver could change the amount of current being delivered to the diode such that its power might drop?

Used to I figured unless the driver explicitly needed sinking I wouldn't, but if you can gain significant stability through that action then it suddenly becomes a different ballgame.

Thoughts?
-Isaac


__________________
ALL MY BUILDS/REVIEWS HERE *CLICK!*
MY BEST BUILDS: Adegan Relic | Aquarius | Frost | Ivy

Been bitten by the shutterbug hard.

IsaacT is offline   Reply With Quote








Old 06-24-2014, 07:24 AM #2
Rifter's Avatar
Class 2M Laser
 
Join Date: May 2014
Location: Vancouver BC Canada
Posts: 572
Rep Power: 52
Rifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond repute
Rifter Rifter is offline
Class 2M Laser
Rifter's Avatar
 
Join Date: May 2014
Location: Vancouver BC Canada
Posts: 572
Rep Power: 52
Rifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond reputeRifter has a reputation beyond repute
Default Re: Power Fluctuations - Attributable to Which?

The electronics efficiency will drop as heat increases, I would always heatsink the driver if there is room to do so. Not only for efficiency but life of the driver as well.
__________________
DIY OSRAM PL520 Camo 501B Host 520nm 80mw
DIY OSRAM PL450B Black C6 Host 450nm 180mw
Laserglow Libra 635nm 5mw
Laserglow Anser 532nm 5mw
Survival Laser S4 Host660nm 300mw
Custom Sinner Host 638nm Oclaro 194mw
Radiant Electronics X4 LPM
Rifter is offline   Reply With Quote
Old 06-24-2014, 11:44 PM #3
Sigurthr's Avatar
Class 3B Laser
 
Join Date: Dec 2011
Location: Michigan's U.P.
Posts: 4,382
Rep Power: 671
Sigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond repute
Sigurthr Sigurthr is offline
Class 3B Laser
Sigurthr's Avatar
 
Join Date: Dec 2011
Location: Michigan's U.P.
Posts: 4,382
Rep Power: 671
Sigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond repute
Default Re: Power Fluctuations - Attributable to Which?

Most CC drivers will automatically correct for drift from temperature though, but yes it is important to heatsink whenever you can. The issue really comes about when the switching element is near the edge of its safe operating area.

However, to answer your original question about starting off high output and dropping low; this is usually a result of being run on batteries with limited current capacity. Batteries can supply less and less current as their voltage (and thus charge state level) drops. You might get 3A from your LiIon at 4.20V, but at 4.11V you'll only be able to pull 2.8A through it. So while your driver, which is set to 2.9A has to limit current initially, there comes a point where it is now "full open" very shortly into the run and current draw will only drop off further. This is common in high current builds. In low power builds it is more likely that heat or lack of sufficient forward voltage (due to raising dropout voltage and lowering cell voltage) is playing the major role.
__________________
Amateur Multispectral Photographer - [X-Ray, UV, Vis, IR]
Amateur Electrical Engineer
Autodidact
Tesla Coil Expert
Sigurthr is offline   Reply With Quote
Old 06-25-2014, 12:03 AM #4
Jstr's Avatar
Class 2 Laser
 
Join Date: Feb 2014
Location: Houston, Texas
Posts: 347
Rep Power: 80
Jstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond repute
Jstr Jstr is offline
Class 2 Laser
Jstr's Avatar
 
Join Date: Feb 2014
Location: Houston, Texas
Posts: 347
Rep Power: 80
Jstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond reputeJstr has a reputation beyond repute
Default Re: Power Fluctuations - Attributable to Which?

Quote:
Originally Posted by Sigurthr View Post
there comes a point where it is now "full open" very shortly into the run and current draw will only drop off further. This is common in high current builds.
Isn't that the point of having a buck or boost driver? So that the current stays constant throughout the batteries' discharge. Because the buck/boost driver can alter the forward voltage, right?

That sounds like it might be the case for a linear driver, however, which might be what you are referring to.
__________________
405nm Cypreus IIb (1W)
405nm Polished Minisaber (<1W)
450nm Ehgemus (2.7W)
450nm Sanwu Silver Series (3W)
450nm Cypreus pen (1W)
450nm Gold leadlight pen (1.5W)
450nm Cypreus pen (1.6W broken)
520nm S4 (200mw)
532nm Ehgemus pointer (100mw)
632.8nm HeNe (.5mw)
638nm Ehgemus (1W)
650nm Sanwu Pocket Pen (200mw)
15W 10.6um CO2 tube
Jstr is offline   Reply With Quote
Old 06-25-2014, 12:25 AM #5
Sigurthr's Avatar
Class 3B Laser
 
Join Date: Dec 2011
Location: Michigan's U.P.
Posts: 4,382
Rep Power: 671
Sigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond repute
Sigurthr Sigurthr is offline
Class 3B Laser
Sigurthr's Avatar
 
Join Date: Dec 2011
Location: Michigan's U.P.
Posts: 4,382
Rep Power: 671
Sigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond reputeSigurthr has a reputation beyond repute
Default Re: Power Fluctuations - Attributable to Which?

A Buck driver can compensate for the declining level of possible current draw from the battery(s) but only until the voltage output from the battery(s) drops to the point where the forward voltage and dropout voltage is no longer sufficient to allow full current to flow through the diode,

A Boost driver exaggerates the current to voltage discharge curve of a battery as it increases the require current draw from the battery, thus loading the cell(s) harder causing them to discharge faster.

A Buck fed Boost (or Buck-Boost) can compensate the best for the discharge curve of the battery(s) but again only until the voltage of the cell(s) can no longer sufficiently overcome the input voltage requirement of the Buck stage at the required current level.
__________________
Amateur Multispectral Photographer - [X-Ray, UV, Vis, IR]
Amateur Electrical Engineer
Autodidact
Tesla Coil Expert
Sigurthr is offline   Reply With Quote
Reply





Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On











Loading








Top 50 Laser Pointer Companies - Green Lasers Top 50 Laser Pointer Companies - Blue Lasers Top 50 Laser Pointer Companies - Red Lasers
Top 50 Laser Pointer Companies - Yellow Lasers Top 50 Laser Pointer Companies - Purple Lasers Top 50 Laser Pointer Companies - Orange Lasers
Top Laser Pointers by Power - 1 Watt+ Top Laser Pointers by Power - 500mW+ Top Laser Pointers by Power - 250mW+
Laser Pointer Database High Power Laser Pointers Laser Pointer Diodes




Privacy Policy | Advertising Disclaimer | Terms of Use


 


All times are GMT. The time now is 11:09 AM.


Powered by: vBulletin
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO
Privacy Policy | Advertising Disclaimer | Terms of Use
Copyright (C) 2017 Laser Pointer Forums, LLC