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PLTB AKA Portable Laser Test Bench (Work In Progress) LOTS-O-PICS

DarkSide

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Mar 19, 2011
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Pardon my lack vocabulary but thats F--kn awesome!
 



Kmor2004

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Jun 12, 2011
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I appreciate the praise except now that I've added the 5V regulator to power the screen, 328, and op-amp, it doen't work.:thinking:

I mean the screen will power up, the board will power up, and I think the chip will power up but sortly there after the chip stops functioning, thought i killed it, but instead it just screws up the code space, so I had re-program the bootloader (kind of like an operating systems for teh chip) and the actual code I wrote for it, but when I still power it up it still stops working after power up....and the 5V reg works since it still powers up the screen and its rated for 1A...so I'm at a loss atm.
 

Kmor2004

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Hey folks I'm kinda back, and I'm reworking my PLTB to be more user friendly simpler but still with all the bells and whistles, minus the 3.8" color LCD touchscreen, I tried to find a similar size serial color LCD, but no luck at least not ones cheaper than the monochrome graphic LCDs I had ($34.95/ea), but so far it looks like I could Offer these new revision ones for about 75-125 dollars if anyone would want one, and when ever I get around to finalising the new PCB (still picking out the right parts and making sure the footprints" are the same) I'll have 2 spare boards that I could either send out with a bill of materials and the schematic/board layout for someone to make as a kit or sell completed units (I'd have to order the parts tho).

However right now I'm stuck on picking a NPN transistor so I need the help of some of out electronics whiz's.

To help explain here's the circuit we're working with:


So my issue is I want to pick a NPN BJT with the propper characteristics For this application, I know I should know how to translate a datasheet for a basic npn transistor, but having 2 different voltages possible plus trying to use it in the linear region rather than to just turn on and off something, not to mention I'd like to get as much of the adjustable duty cycle range as possible out of the transistor (e.i. if my uC has a max freq counts on the timer of 2000 I'd like to be able to adjust the on time of the square wave from 200-2000 and be able to A LOT of the current limiting options), as it stands now I just tested the old PLTB board with a test code to drive the PWM signal for .0005% to 99.999% on time and I couldn't get my 445nm to start emitting light (yes I did look into the laser) at 50%, so I'm asking for your guys help with determining a good better transistor to use or at least throwing some advice my way since most of the web pages I've looked at to help me figure it out have all been referencing it as a switch in a circuit.

To help, the uC is running on +5V the pin can source a MAX of 20mA, R4 hasn't been set in stone yet but I'm thinking 280-320 ohms I'm leaving the cap at 10uF electrolytic.
 




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