445nm test load questions.

I'm gearing up for a 445nm build with Kenom's Kryton Groove group buy. From reading here, I think my best bet is to use a Dr. Lava Microboost http://hacylon.case.edu/ebay/laser_diode/Micro_BoostDrive.php and I'll get it set to 1000mA.

So for when I do the final pot adjustments, I'll want a test load.

Is the standard design first posted by HIMNL9 like this one here: Test Load Thread



... what will work appropriately for a 445nm I want to run at around 1000mA?

Should I use 1/4W or 1/2W resistors? These value packs from http://www.futurlec.com/ValuePacks.shtml would work fine? Also a probably dumb question, does it matter? I know the color codes for reistance 1 ohm = brown black gold gold etc. Is it the same by wattage?

Also, what does the chain of diodes do that one diode alone does not?

That will work fine. But the test load gets really hot quick few seconds to be exact.

So the way i used it is i would only leave the test load on for a few second turn the pot a little more on the driver as much i could wail it was on then turn the power off and let the test load cool down then i would turn it back on turn the pot some more then let the test load cool down again and just repeat those steps until you reach your desire mA.

There might be other methods of doing this but i found it easier for me to do it this way.

AJ_Dual said:

Also, what does the chain of diodes do that one diode alone does not?

Click to expand...

The diodes simulate the voltage drop that the real diode will have on the driver. 4 diodes for a red LD and 6 diodes for a violet/blue LD

Ah. Thanks. I didn't think about the drop the diodes would add.

And no difference between 1/2 and 1/4 W resistors?

AJ_Dual said:

And no difference between 1/2 and 1/4 W resistors?

Click to expand...

The quantity of smoke that they produce, and the time for which they produce it .....

Seriously, the resistor need to hold the current that you are testing, and to dissipate the resulting power ..... easy ohm law, power is volt*ampere, so, if you use an 1 ohm resistor, for test a 500mA drive, it have a dropout of 500mV across it, and need to dissipate 0,5*0,5=0,25W (1/4W), if you test it with 1A, it cause a 1V dropout, and need to dissipate 1W, if you test 1,5A, it cause 1,5V dropout and need to dissipate 2,25W, and so on .....

And, ofcourse, more high is the power of the resistance, more it's robust and affordable, and less risk to smoke out it .....

So, is always better to use at least an 2W resistor, for currents under 1A, and at least 5W resistor for higher currents.

Thanks!

Since I plan on setting the driver to 1000mA, I should use a 5W resistor.