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-   -   Solved -Anyone else experience a diode this inefficient? (http://laserpointerforums.com/f65/solved-anyone-else-experience-diode-inefficient-89448.html)

petters 05-23-2014 07:13 PM

Solved -Anyone else experience a diode this inefficient?
 
I decided to actually start putting some stuff together so that the last thing I would need is a driver. I assumed that around 5-7V would be the reasonable range for a 9mm 445nm (NDB7875) to draw 2.3A. Of course I plan on using a CC driver, but I decided to run a little test on the diode.

http://i.imgur.com/VrhcYeg.jpg

Now before anyone says anything about the driver I am using to run the test, it is not that bad of a driver. I have checked the output on an oscilloscope and it is surprisingly clean. Now, that aside, 8V for 2.3A? So much for 7.4V to power this thing :crackup:, will obviously have to use another diode but just wanted to see if I am alone in having a dud for this specific diode.

IWIRE 05-23-2014 09:20 PM

Re: Anyone else experience a diode this inefficient?
 
I didn't even know that diode could withstand that voltage. Mine are usually right about
5v @ 2.4a. What is the diodes output in mw ? Have you double checked with a different meter ? That would freak me out. I would have stopped long before even 6v and thought I had a problem.
Are you sure that setup is good ? I had one like it I got from Ebay, that thing would read all kinds of crazy stuff and none of it was right.

Blackwolf 05-23-2014 09:22 PM

Re: Anyone else experience a diode this inefficient?
 
is the output like this? http://laserpointerforums.com/f65/su...140-85310.html

petters 05-23-2014 09:42 PM

Re: Anyone else experience a diode this inefficient?
 
Quote:

Originally Posted by IWIRE (Post 1301068)
I didn't even know that diode could withstand that voltage. Mine are usually right about
5v @ 2.4a. What is the diodes output in mw ? Have you double checked with a different meter ? That would freak me out. I would have stopped long before even 6v and thought I had a problem.
Are you sure that setup is good ? I had one like it I got from Ebay, that thing would read all kinds of crazy stuff and none of it was right.

Yeah I might have to check it against my actual multimeter to be sure it isn't just an issue with this driver, which seemed to be working well since I hooked it up to a 1 ohm resistor and the current matched the voltage.

Quote:

Originally Posted by Blackwolf (Post 1301070)

Haha actually checked that thread to see where the issue may lie. Here are the raw outputs, at 0.5A and 2.3A:

http://i.imgur.com/pns8YpD.png

I thought they were clean :thinking:

petters 05-24-2014 12:29 AM

Re: Anyone else experience a diode this inefficient?
 
Welp just threw another diode onto it and it gets the exact same results.... :cryyy:

Edit: Could it be the wiring? I mean at such a current there could be a significant voltage drop over such a long wire, right? Wire length is about half a meter for both terminals.... lol might be the issue here

.........ISSUE SOLVED, wire length was the issue ;)

IWIRE 05-24-2014 01:08 AM

Re: Solved -Anyone else experience a diode this inefficient?
 
Ha ! Cool ! Glad you got it sorted out ! Thanks for posting what you found. REP +1 :beer:
Flaminpyro had warned me about wire length causing problems with certain drives. I try to keep them short now. Great troubleshooting. That's one of the things that I find fun about this hobby. There are always opportunities for solutions :)

Bionic-Badger 05-24-2014 03:09 AM

Re: Solved -Anyone else experience a diode this inefficient?
 
Hey Petters, you can calculate the voltage drop as a function of wire resistance using a chart like this. I'd be curious to hear how much voltage you were dropping. If you're using some 26 gauge wire like that silicone wire sold by FlamingPyro, 0.5m (1.6ft) would be about 0.067ohm resistance. At 2.3A, that's only a 0.1541 volt drop, which isn't huge, all things considered.


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