On 01/25/2012 01:43 PM, Viesturs Lācis wrote: > 2012/1/25 andy pugh<[email protected]>: >> On 25 January 2012 21:07, Viesturs Lācis<[email protected]> wrote: >> >>> Kirk, I am getting totally confused... >>> What is the difference in schematics between both images in Your last >>> email? I cannot see any... >> >> The direction the arrow points in the transistor schematic symbol. > > Ok, thanks! > I do not understand - that is inside the BD139, right? What can I do > about it, if it is still the same BD139 transistor??? > > I finally managed to get at least something working: > Short-circuiting +5V to 4N25's pin5 turns the laser power on and off > as required. > I am left with an impression that 4N25 is not working correctly. > > Is that diode next to R1 mandatory? I will not have a time to obtain > one and solder in, before going to client. > I just hope that I have spare 4N25... > > How sensitive to soldering heat are things like 4N25 optoisolators? > Maybe I have accidentally burned it? > > Viesturs
I'm following this thread for a while now and believe that solution lies in managed current supply, not voltage. I see no current check in the suggested circuit. Specialized circuits will provide much longer life for your laser, better max current limit, inrush current, and you can drive it with PWM to run cooler. Perhaps "generic" LED driver circuit is the way to go: http://www.maxim-ic.com/datasheet/index.mvp/id/4510 While low power, same rules apply: http://www.maxim-ic.com/app-notes/index.mvp/id/242 There are probably other ICs to drive laser diodes. Laser you mentioned is in a way another type of LED but I might be wrong here when it comes to driving it properly. Still, I would be more confident to use any current source with a limit to drive the laser diode than use circuits discussed earlier. -- Rafael ------------------------------------------------------------------------------ Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
