Building a linear driver, a couple questions.

So I've spent the day reading threads like this:

http://laserpointerforums.com/f67/how-laser-diode-drivers-work-explanatory-thread-71513.html

watching the soldering tutorial video (I had some basic knowledge and experience before, but it was very in depth and I learned a ton)

I went through a build guide


My goal for this driver, is to make a good 405 nm laser pointer for general pointing and burning and other lasery fun things. I will not be attaching it to shark-foreheads. The diode I'm looking at is the following:

PHR805T 120mW 405nm TO18 Laser Diode Violet Laser Diode 2 Pcs | eBay

also, The owner of the electronics store recommended a turner-style potentiometer/trimmer. I picked up a 25 turn 50 ohm turner.
64y-500 on this sheet
http://www.nteinc.com/pot_web/pdf/64y_series.pdf

Will this work?


I want to run the laser off a LiPo battery like this:
Gens Ace Lipo Battery 650mah 3.7V 15C

Ideally, the laser would be housed in a 1" wide (lightsaber shaped:eg cylinder with a fan on a separate circuit and a good heatsink on the diode for longer continuous duty cycles. I was also considering a Laser diode socket to make full use of the circuit by allowing me to interchange diodes (for either replacement, or changing colors on the fly.)

Is this wise? or should I stick to the basics for my first build? Any recommendations/cautions?

I intent to solder the bulk of the circuitry to a mini protoboard.

I tried to read up on everything, so I apologize if there are glaring mistakes.
Thanks in advance!

You haven't actually told us anything about the driver you will be using.

A single lipo cell does not have enough voltage to operate a violet laser diode with a linear driver. The load voltage of a linear driver must be lower than the supply voltage by the "minimum dropout" voltage which depends on the driver used. Violet diodes are something like 5-6V. This also means the cap you've chosen will fail. Use a smaller capacitance with a higher voltage rating.

The capacitor is a 50v, not 5. Is 100MFD too high?

I typoed. So a 2 cell lipo would run it fine then?

Thanks for the info on the voltage. The rest of the circuit is basically identical to the DDL driver.

instead of trying to understand what you were trying to say, i'll tell you what i made for my 405nm diode
I used a LM-317 regulator with a resistor that was about 4 ohms to output 500mA. There are however different lm-317s some can output 1.5A and some output 1.25A i beleive. for a capacitor i used a 100uF cap across the pins of the diode Trust me on this: IT IS EASIER TO BUY A PRE MADE DRIVER. They are smaller, more reliable and just as cheap (almost)
-Josh

NKO29 said:

There are however different lm-317s some can output 1.5A

Click to expand...

They are all rated for up to 1.5A. You set the current with a resistor. Maybe you mean similar variations like the LM350 and LM338 which are rated for up to 3A and 5A respectively. Those can still be set to half-amp though.

Okay, based on what you guys said, and further reading, I think I got it. I'll post pictures when It's done.

Cyparagon said:

They are all rated for up to 1.5A. You set the current with a resistor. Maybe you mean similar variations like the LM350 and LM338 which are rated for up to 3A and 5A respectively. Those can still be set to half-amp though.

Click to expand...

You're probably right, i havent used one in quite a while I think around 1.2V might have been the lowest voltage or something.

But yeah with so many different regulators you have plenty of choice when it comes to power. Good luck, make sure to show the final product