Grotesquely Freakish PHR diode...

[wolfblue]

You probably did not hurt the LM317 or the voltmeter. Might be a good way to hurt a laser diode though.

And it would be quicker to build a dummy load yourself. I think Radio Shack sells a 50 pack of diodes for a few bucks. There should be about 10-12 1N4001's in there. And some 1N4002 diodes. Both are good for a dummy load. You put the dummy on the driver INSTEAD of the laser diode. Then power the driver and set your desired current. Then remove the dummy, SHORT THE OUTPUT CAPACITOR on the driver to remove any charge. A common mistake is to forget to empty that capacitor. You forget and 99% you kill the laser diode. Now install the laser diode. Don't get in a hurry when doing this stuff. Impatience kills more diodes than anything else. Check yourself twice before you do anything. Wait a minute and then check again.

The dummy works because all those rectifiers have a voltage drop that adds up close to the laser diode's voltage drop. OK not really. But its close enoegh so that the driver behaves as if the laser diode is connected. Four diodes are real close for a red laser. Six is not as close but still will be within a few mA end result on a Blu-Ray. I usually build Lab's so I have room for a shunt between the driver and laser diode. But I still use a dummy to check my driver.

And DONT FORGET TO SHORT THAT CAP when you take the dummy off.
And don't ask how I know Impatience kills diodes more than anything
And anybody please correct if I'm wrong anywhere

--John

 

[pianoman2011]

You probably did not hurt the LM317 or the voltmeter.  Might be a good way to hurt a laser diode though.

And it would be quicker to build a dummy load yourself.  I think Radio Shack sells a 50 pack of diodes for a few bucks.  There should be about 10-12 1N4001's in there.  And some 1N4002 diodes.  Both are good for a dummy load.  You put the dummy on the driver INSTEAD of the laser diode.  Then power the driver and set your desired current.  Then remove the dummy, SHORT THE OUTPUT CAPACITOR  on the driver to remove any charge.  A common mistake is to forget to empty that capacitor.  You forget and 99% you kill the laser diode.  Now install the laser diode.  Don't get in a hurry when doing this stuff.  Impatience kills  more diodes than anything else.  Check yourself twice before you do anything.  Wait a minute and then check again.

The dummy works because all those rectifiers have a voltage drop that adds up close to the laser diode's voltage drop.  OK not really.  But its close enoegh so that the driver behaves as if the laser diode is connected.   Four diodes are real close for a red laser.  Six is not as close but still will be within a few mA end result on a Blu-Ray.  I usually build Lab's so I have room for a shunt between the driver and laser diode.  But I still use a dummy to check my driver.

And DONT FORGET TO SHORT THAT CAP when you take the dummy off.
And don't ask how I know Impatience kills diodes more than anything
And anybody please correct if I'm wrong anywhere

--John

I’m glad that I didn’t hurt my voltmeter. I use that thing so much. I would go to Radioshack and buy some diodes but:

a) The Radioshacks here really suck… all they carry is consumer electronics like cameras and phones. Barely any electrical components any more .
b) I already ordered one of the rckstr dummy loads.

But I will build one based upon your instructions if my rckstr dummy load breaks . Thanks!
And about shorting out the capacitor, don’t worry… I have already killed two diodes (one PHR, one 4x) because of forgetting to short it out. I have officially learned this the hard way . I am so paranoid about that now that I even installed a constant off switch that shorts out the cap any time I press the button. This is being used because I am going to be running two diodes (one 405nm, one 650nm) off of one LM317 driver. I have them both attached to the same ground and positive wires except some resistors spliced into the positive wire leading into the 405nm that reduce the current from around 400mA to 140mA. Anytime I switch from 650nm to 405nm or vice versa, I’m gonna’ give that button a click! No more capacitor assassinations for my precious diodes!

And patience is a virtue that I am finally starting to get a hold of. When I got my first PHR ever (from our school post office), I ran to my dorm room (skipping my last class of school) and tossed everything off of my desk onto the ground to make room to solder the diode to my driver. I actually broke a couple of my possessions in the process... and blew the diode within thirty minutes. That was an extreme example of how bad my ravenous laser cracing rampages could get... extreme excitement! Now I am a bit more controlled ;D ;D ;D.


Anyways, thank you for all of the information… after a month of cluelessness, I finally understand how a dummy load works and why I need one. You have been very helpful !

-Jakob

P.S. Sorry for the lengthy response… just playing with my new 50mW 532nm laser and very hyper right now… [smiley=2vrolijk_08.gif]

 

[leukoplast]

You would think that your 100 mAh batteries would run something at 100 mA for 1 hour.  Tot bad it doesn't work out that way.

I pull 8 amps or more out of my RC cars 2800mAh batteries.  Not all full throttle, and it lasts about ten minutes.  I just did not think a 9V alkaline could dump a half amp.  Or even a quarter amp. I think they are rated around 500 mAh.  I did not think it would come out of those little batteries so fast.  But thats just what I think  Maybe it will dump that fast.  But maybe it was only putting out like 200mA.  Jakob did say it was not much brighter @650mA than @200mA.  I think it might do that at 650mA( there I go thinking again). But it could be the battery reached its limit.


--John

Well, that sorta makes sense. If you are pulling 8 amps from a 2.8amp per hour source...it will drain very fast.

Really, the flow depends on the voltage. Think about this, a car battery is only 12 volts, and it can put out enough current to literally rip chunks out of metal and destroy stuff (with lack of battery words). So even with 9 volts you should be able to pull lot of current from these little batteries.

In terms of analogy, think of a gas station. Volts is the size of the hose/pipes, and mAh is the amount of gas under the ground. Obviously the bigger the hose, the more is will drain. And at 9 volts, you can drain really fast. Although there would be pressure involved as well, and I cant remember what the analogy for that would be.