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pfred1

pfred1

on April 15, 2015

Thread Title: Getting set to build a laser pointer here


rtecoder said:

Your schematic looks fine, and nearly matches the sample circuit from the 317 datasheet.  Using your values, it looks like you would be regulating to a 4 mA current.  Your results will vary depending on the load you are using.  No load should result in a 1.2V output, a diode may result in the forward voltage of the diode being the output, but you may need a parallel resistive load to trigger the 317 to get the output voltage above 1.2V.  When you get your parts, breadboard and test it out.

Since you said you were building a laser pointer, you may want to look into a voltage thief circuit instead so you can run your pointer from a since cell battery, instead of what I'm guessing would be a 9V.  It does need a few parts that you may not have, but overall it's not a complex circuit either.



For sure I am going to spend some time on a breadboard testing out various things. Ideally I'd like to run on these 7.2V rechargable tool batteries I have. To do that I might need to put a voltage regulator on those though. That shouldn't be an issue. I am getting 10 LM317 ICs with my diode order.

pfred1

pfred1

on April 15, 2015

Thread Title: Getting set to build a laser pointer here


sgray74 said:

pfred,

Your schematic is looking good.  Glad to see you did not put a capacitor on the output since you are using it for a constant current regulator.  Some people say to put them on there to stabilize things, but you should not have one when using it as a current regulator.

I can't wait to see your project when it is done.

What voltage is your laser diodes you are getting?  If you have time to wait...here are some that I bought..but they are in china and will take a little while to arrive....

http://www.electrodragon.com/product/laser-point-header-module-650nm-infrared-detector-readable/

The Operating Voltage is 3V and the Operating Current is < 45 mA....just a thought.



Thanks for the reply. I was wondering about the output stability capacitor. I've heard not to use it, so I left it out. I am shooting for 5ma with my output.  That is what the diodes I am getting are rated for. They are supposed to be 3V diodes too. I am getting a 10 pack, so I probably will blow a couple of them up, just to see what they can really do. It is not like I need 10 pointers. Just one good one should suffice.

I am thinking about heatsinking it too. They come in little brass holders, but I am thinking a larger aluminum heatsink might help them out? Until I actually get the things I don't really know about any of that. Supposedly this brass barrel they're in has an adjustable collimating lens in it. Some say the whole affair is very fragile too, so I might not be able to mount them into a press fit heatsink too easily without breaking them?

Then again I have some machine tools so I might be able to rig something up here.

pfred1

pfred1

on April 13, 2015

Thread Title: Getting set to build a laser pointer here

Depending on how this goes I might post the project here. As of yet I have not built anything though. Although I have designed some simple circuits already. I'm waiting for the parts I ordered to arrive. I have researched the topic a bit on the 'net and I am thinking about building a very simple current regulator for the laser doide I am getting.

 

This is all new to me though so I figured I would post my schematic here to see what kind of feedback I get about it. I may have missed something critical that I am not aware of.

pfred1

pfred1

on March 1, 2015

Thread Title: New Member Saying Hi

Hi,

My name is Paul and I just saw a post on Google+ that had a link to this site in it. This looks like the sort of thing I like so I made an account. Hopefully soon I can put up something here.