Where can you salvage a LM317?

[Brett]

You're trying to simulate the forward voltage of the diode in question, which should be about 2v... 3 of them should do it. Make sure your diodes are capable of handling that sort of amperage though.

Yeah, that makes sense. According to Snoctony's data for his C-mounts...2.0v and 2.2v respectively for the 500 and 1000mW pumps. Great! I have some bigger diodes, such as the 1n5404, which are 400prv 3 amp.

-Brett

 

[Benm]

Do measure what you are doing though, diodes like the 1n540x series have a forward drop of over 1 volt each at full rated current (3A). So if you are using 3, the result will be 3 volts, not 2.

 

[Brett]

Do measure what you are doing though, diodes like the 1n540x series have a forward drop of over 1 volt each at full rated current (3A). So if you are using 3, the result will be 3 volts, not 2.

definately.  I've been trying to measure as much as I know how in this type of circuit, although it will probably take me a while to track down a 1 Ohm resistor (for measuring mV == mA) in my bin or reisistors, as it seems most of what I have on hand are multi k larger sizes.  I also need to figure out what value reference resistor to use with my 25 ohm pot.  

I just finished soldering my 2 x 1n5404 resistor dummy load together.  I had to solder smaller leads to the heavy gauge leads on the beefier 540x diodes so they could plug into the prototype board.  

I am getting ready to plug in the dummy load (for now without the 1 ohm resistor) and start trying different reference resistors.  

If I understand this correctly, I need to try different components until I see around 2.0v across the load?

-Brett

*edit* -- Ok, I've measured the voltage across the dummy load as well beneath 2.0v. So I decided to try it out on the spare DPSS module I have and just risk it. Unfortunately I can't measure current right now, because I don't have a good ammeter than can do mA, nor do I have a 1 ohm resistor to use the mv method. I tried it out, (while measuring) and the highest voltage I saw across the LD was 1.6 volts. I am guessing it was still under the current threshold for the c-mount since there was no output whatsoever from the laser.

 

[pseudolobster]

The driver is being used as a fixed current source, the voltage will depend on the impedance of the load, not any setting on your pot. In this application the 317T is always trying to stay at the same current, in doing this it varies the voltage. You can't derive any meaning from measuring voltage across the driver.

You can use other values of resistors other than 1ohm, it's just the precision goes down and you need to do a bit of math to figure out the amperage. Or, if you have a bunch of resistors of the same value you can wire them in parallel, halving them. (for example you could use two 2ohm resistors instead)

 

[Brett]

Thanks for the detailed description Pseudo.

I have had success using this driver to power my AixiZ module whose driver had died a few days ago!
However, I did have to remove the resistor and go without it, since I don't have any small value (like 2 x 10 ohm) resistors around right now.  I was pretty excited when that DPSS module started lasing!!

You can see the dummy load of 2x1n5404 diodes sitting on the prototype board (not plugged in).

 

[Brett]

Here's a picture of the spot on the wall about 10 feet away...the spot size is exaggerated by the brightness and ISO setting of the camera.

 

[ElektroFreak]

Nice!! Not bat at all considering it's your first one. Is the laser any brighter on the 317 driver? You had said it was less bright than your 15mW..

 

[Brett]

Nice!! Not bat at all considering it's your first one. Is the laser any brighter on the 317 driver? You had said it was less bright than your 15mW..

Thanks!!!  It is quite a bit brighter than the original AixiZ driver and the Snoctony driver as well.  There is a sweet spot on the 25 ohm pot where power seems to be at its highest point.  I'm planning on doing some relative power measurements using a meter and a solar cell as soon as I get time.  I'll start another thread for that I guess.  

It's nice that this runs off of a 9v (although I think it's pulling it down pretty fast).  I will definitely be working on some portable 532nm dpss projects soon based on this simple driver.  My next step with this driver will be getting some perboard with the copper clad holes and building a more permanent version with the other LM317.  I'll probably leave this prototype around for a while for experimentation with different LDs I get in the future.

-Brett

 

[ElektroFreak]

^good to hear that it's working right finally. On thing you could try is using a 9V wall adapter to power the 317 driver if you don't necessarily need it to be portable, and don't want to worry about draining batteries. Just make sure you observe the proper polarity. If you place a 1N4001 diode in series with the positive input of the driver, it will protect everything from damage from reverse polarity. I recommend doing this with all drivers just on the off chance that polarity would be reversed. It'll protect both the driver and the diode

 

[Brett]

Yes, I will search around here for a 9VDC wall adapter. If I get time tonight I am going to start on another driver with the 2nd LM317T. It will basically be a clone of the first, but will be more of a "finished" version...soldered onto some copper clad perfboard (unless I actually come up with a PCB design and etch a board). I will incorporate another diode to prevent reverse polarity hookup of the power supply. Except......wouldn't I need one that could handle the currents in a DPSS situation (up to 1.5A or so), yet would not drop the voltage too much. Of course I could use several diodes then and just just a 12v wall adapter in that case. I think I have plenty of those sitting in a box somewhere.

I wanted to say to anyone following this thread. I went from having a 50mW green dpss module with a dead power supply, to having a working one after just a few hours work...and I found that LM317 regulators seem to be plentiful and easy to salvage from taking things like old battery chargers apart. I'm sure you could find this, and other usable regulators in old PC supplies too.

-Brett

 

[ElektroFreak]

Yes, I will search around here for a 9VDC wall adapter.  If I get time tonight I am going to start on another driver with the 2nd LM317T.  It will basically be a clone of the first, but will be more of a "finished" version...soldered onto some copper clad perfboard (unless I actually come up with a PCB design and etch a board).  I will incorporate another diode to prevent reverse polarity hookup of the power supply.  Except......[highlight]wouldn't I need one that could handle the currents in a DPSS situation (up to 1.5A or so)[/highlight], yet would not drop the voltage too much.  Of course I could use several diodes then and just just a 12v wall adapter in that case.  I think I have plenty of those sitting in a box somewhere.

I wanted to say to anyone following this thread.  I went from having a 50mW green dpss module with a dead power supply, to having a working one after just a few hours work...and I found that LM317 regulators seem to be plentiful and easy to salvage from taking things like old battery chargers apart.  I'm sure you could find this, and other usable regulators in old PC supplies too.

-Brett

Yes you definitely would. Sorry, I always think of LM317 drivers powering small diodes since I don't usually use them with DPSS. Just one diode should be plenty of protection against reverse polarity, just don't leave it reversed for very long...

 

[Brett]

Is there anything cool in the way of a home made DPSS supply that I could find on this forum.  Any threads along those lines you could link me up with?  I mean, the LM317 would do fine for 500mW pump diodes, and maybe 1000mW (although I probably could not max them out or push them to the top of their current range), but at some point in the future I will probably want a more powerful driver.  I guess there are a lot of ideas for drivers in Sam's Laserfaq...but actually there are so many it's really hard to narrow it down.  Also, someone on here mentioned that the section on drivers in the Laserfaq is somewhat out of date.

Maybe SMPS technology has progressed a bit since then.  I know a little bit about that and have a small amount of experience, but most of the topologies I worked with were H-bridges and half bridges of high current (like 200A) power mosfets switching power into a resonator in a self-resonant feedback tuned tesla coil.  My electronics experience is mostly geared around trying to get high voltage efficiently, rather than keeping a sensitive expensive LD happy.

On a similar note (still somewhat on topic), a friend has mailed me a hybrid Nd:YV04/KTP crystal in the mail for use in my first from scratch DPSS laser.  My 2nd LM317T supply (which I will solder up tonight if I have time) will probably be used on this project.  I wanted to get a fiber coupled 808 with a nice 50 or 100um spot size, but I can't seem to find any on ebay right now.  I am tempted to take the C-mount out of that AixiZ module and try with it.  We'll see...I'll probably just go the rational route and wait...why mess up a working module?

-Brett

 

[ElektroFreak]

You could message Snoctony in ebay. He may know where to find you a fiber-coupled diode.. Have fun with that hybrid but don't get spoiled. When you eventually get into discrete crystals and optics, alignment gets a whole lot more hairy..

As far as DPSS resources go, Sam's Laser FAQ is the best source of laser knowledge to be found in one location. I may have given this link to you already, but if not here ya go: http://www.repairfaq.org/sam/laserfaq.htm

 

[Brett]

You could message Snoctony in ebay. He may know where to find you a fiber-coupled diode.. Have fun with that hybrid but don't get spoiled. When you eventually get into discrete crystals and optics, alignment gets a whole lot more hairy..

As far as DPSS resources go, Sam's Laser FAQ is the best source of laser knowledge to be found in one location. I may have given this link to you already, but if not here ya go: http://www.repairfaq.org/sam/laserfaq.htm

Yes, you did give me the link in a prior reply, and I have been familiar with the DPSS section of the LaserFaq for some time.  I've read it all the way through once, but I often refer to it for information, and to just ensure that certain concepts are really pounded into my brain.  Thank you again anyway, you've been very helpful to a DPSS novice.

I will try not to become spoiled using the bonded crystal.  I understand that it's probably only good for about 100mw or so (I don't have the measurements yet) and I probably won't get that out of it.  Eventually I will want to make the jump to using discrete crystals/optics and learning the patience that is required to get them properly aligned.  I hear that it is a difficult, tedious process.  I guess I just wanted to start out simple, and work my way up to the high powered stuff in a linear fashion.  That way I can be safer and learn more in the process.

-Brett

 

[r3tr0]

If you're in the US, I can send you three (3) via regular mail (1.5A versions). *I bought 50 of them on eBay for some amount, and will never get through them all.

can you send one?

 

[diachi]

can you send one?

Check the date on this post ... the last reply was in 2008. Please avoid digging up old threads (in this case, really old, at ~9 years old) unless you're contributing something.