My newbie laser building project...

[Gendo]

You have been helpful though.

If anything, this thread will help out anyone else who buys Will's PHR kit off Ebay.

 

[dr-ebert]

The input voltage required by the DDL driver is NOT 6..7.2V. It depends on the voltage requirement of the load you attach to it, i.e. the laser diode in this case. Input voltage should be at least that much plus 2.5V (give or take a little). Having less means the driver is "out of regulation" and the output current will be less than you want. Having more is no problem, the excess voltage will be converted to heat in the circuit (of course, there will be a max voltage above which the circuit will be damaged, I don't know what it is but would suspect at least 12V).

So for a RED diode 6V in is a good choice; for a blu-ray, it should be 9V (can be more, shouldn't be [much] less).

As for the press fit for the diode: it's only the bottom brass part which should fit tightly. It has a standard diameter of 5.6mm (with 0.05mm tolerance) so I guess a 5.5mm hole should be right., the brass bottom has some wedges cut out so it can give. The can above should not fit tight! A 4.5mm hole should have enough leeway.

 

[rog8811]

All you need to know about the LM317 circuit on one page.
http://www.rog8811.com/laserdriver.htm
It is a distilation of what had become a very long thread:yh:

Regards rog8811

 

[Gendo]

Don't go with your way of setting the pot. there are so many pots out there. 1 turn 2 turn half turn. see what i mean. here is a pic of how to make a super duper simple dummy load for setting your driver. and once you have it made, depending where you place the resistor, you will always have it. you can thank rog8811 for this one. hope it works out. oh, also this just hit me, don't widen the hole but you can bevel the edge. and yes if the glass breaks it still can be used if you safely get out the debris.

Only one problem I see with this diagram. Radio Shack doesn't carry 1 ohm resistors. The lowest I see there is 10 ohm resistors in the sub-watt range. Does the wattage even matter?

Would someone clarify for me what resistor is required for the dummy load, preferrably before RS closes this evening?

 

[rog8811]

Use a 10ohm, all you have to do is divide the mv reading by 10 to get the ma.

Regards rog8811

Edited... to remove error.....

 

[Gendo]

Ahh, thanks Rog. I had bought a 1k ohm pack (1/2w, 5%) thinking maybe the "k" was left out, so I'll go exchange them.

Even though it's a pretty good copper/aluminum heatsink/lens assembly, I just want to be sure this time that the ma is around 50-60 so the diode lasts a while.

 

[Gendo]

Use a 10ohm, all you have to do is multiply the mv reading by 10 to get the ma.

Regards rog8811

I hope you meant divide not multiply because I'm getting readings of 107mv at the least and 1.01v at the most on the pot.

My multimeter also has an amp setting and connecting it the same way as your diagram gives me 9ma and 90ma respectively.

 

[b52productions]

confused ????

Hello, i have ventured into a project and it looks like i skipped a step!!

I never used a dummy load to set the current nor did not adjust for "voltage drop":anyone: not sure how that works ?

This is what i have:

Computer power supply output 4.93v wired to a homemade Adj Lm317
voltage regulator tuned to an output to 2.83v as directly tested with digital multimeter for volts. The curcuit is similar to this:

This 2.83v is fed to my constant current driver:

I then tested the output of the constant current driver for voltage with multimeter ( 2.8v) Not much of a drop but no load just multi meter.


Next i adjusted the current pot to output of 180ma (no dummy load)

Questions:

1. Does my current needs to be adjusted while using a dummy load?
2. is the diode geting 2.8v or actually less ? as i have measured
no voltage drop. But then again im not measuring things correctly.
3. my blue diode driver was set up with the same 4.93v input and
may need to be adjusted also as its output was adjusted without a
dummyload.

From what i have read i should:

1. remove the lm317 curcuit and feed the 4.93v to the constant
current driver
2. Disconnect diodes, adjust with dummyload 1mv=1mw {already built one}
3. make sure power is discharged before reconnecting diodes

But not making any changes until advised

Any help is greatly appreciated:banghead:

Thanks in advance
dudley

 

[rog8811]

I hope you meant divide not multiply because I'm getting readings of 107mv at the least and 1.01v at the most on the pot.

Sorry brain fade...it comes with old age....I will edit my post, I don't like to leave wrong info on threads.

Regards rog8811

 

[rog8811]

DP

1. Does my current needs to be adjusted while using a dummy load?
2. is the diode geting 2.8v or actually less ? as i have measured
no voltage drop. But then again im not measuring things correctly.
3. my blue diode driver was set up with the same 4.93v input and
may need to be adjusted also as its output was adjusted without a
dummyload.

The idea of the dummy load is to try out the settings of the driver with, as near as possible, the same load as it will have with the LD on it.... If you get it wrong with the dummy load all you will get is a warm resistor, get it wrong with the LD and you get an expensive LED.
You will get no usable readings from the driver with no load.

As the LM317 needs a voltage overhead of three volts the most you will get out of the driver, under load, is a smidgen under 2v.

1. remove the lm317 curcuit and feed the 4.93v to the constant
current driver
2. Disconnect diodes, adjust with dummyload 1mv=1mw {already built one}
3. make sure Capacitor is discharged before reconnecting diodes

This sounds ok but I do not know, from the photo, what the drivers are, do you know how much voltage overhead the regulators need? (LM317=3v Rkcstr=2.5v). plus the blu ray will need 4.5v.

If it is a boost and buck curcuit it may be ok.

Regards rog8811

 

[Gendo]

Sorry brain fade...it comes with old age....I will edit my post, I don't like to leave wrong info on threads.

Regards rog8811

No worries. I got it up and running last night just in time to go out and amaze my buddies around the campfire up in the mountains.


A special thanks to you Rog for all your help!!!

 

[pseudolobster]

Computer power supply output 4.93v wired to a homemade Adj Lm317
voltage regulator tuned to an output to 2.83v as directly tested with digital multimeter for volts. The curcuit is similar to this:

This 2.83v is fed to my constant current driver:

I then tested the output of the constant current driver for voltage with multimeter ( 2.8v) Not much of a drop but no load just multi meter.


Next i adjusted the current pot to output of 180ma (no dummy load)

In your first step it seems you've made a constant voltage regulator to feed to your 2.8v (boost?) driver... I think you can skip this step, as ATX computer power supplies provide 3.3v output on pins 1 and 2, which should be in range for your driver... Adding a voltage regulator to step down 5v is an unnecessary step which only serves to generate heat.

Questions:

1. Does my current needs to be adjusted while using a dummy load?

Yes. With no load, the driver should be producing (nearly) no current. You really do need some load in place drawing the correct voltage for your current measurements to be valid. Try 6 diodes in series.

 

[Gendo]

My Nikon's stock lens doesn't do macro very well, but I finally took a few pictures to better show how I put it together.

The board must be notched on the corners so the center section of the flashlight housing pins the board against the heatsink. Make sure the board's width allows the diode pins to be on the pot side of the board, or you'll risk shorting on the soldering on the other side. I carefully tapered those sides and scratched off the outer rows of copper squares as well. My earlier rendering shows how many 1/10" squares in size the board should be.

Also. if you use Ultrafire batteries, you'll have to tweak the contacts in the battery holder to make contact with the positive ends of the batteries.

Something that reflected blue instead of violet. It's extremely bright blue on white cotton or white 100% acrylic paint. Now the hunt begins for some kind of translucent cover for the lens that'll also make it work as a flashlight.

One final thought. You could mirror image my circuit layout, and then turn the LM317 around so when it's bent over the metal tab on it is further from the side of the housing. However, I set it up this way so the LM and the blue cap help keep the circuit board from moving around.

Thanks again to those of you who helped me out, and thanks to Will (the guy who sells the kit) for your help as well. Overall, it was a fun puzzle to figure out.