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LD died

ultimatekaiser

ultimatekaiser

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Ok so I'm a complete idiot and I think I shorted out a diode on a stupid mistake.

Maybe you guys can clear this up for me.

how would you hook up a diode that is case +?
conversely how would you do a case -?
I think i just reversed the polarity on my diode and LED'd it. it lights, but only very dimly now.


the diode pinout its LD cathode(-), common LD anode (+) and photodiode Cathode as the case, and then the photodiode Anode
 
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Eudaimonium

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I don't think the polarity is the problem. If you got that wrong, there'd be no light at all.

You're right, the diode went LED. What I'm worried about is your driver setup. Any pictures or aditional information would be great.
 
ultimatekaiser

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It's an Lm 1117 driver and I'm going to use two 3.7v batteries to power it. The diode needs 2.5V and around 90-100mA I'm at work ATM so I can't take pics.
 
NKO29

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TBH i dont actually think shorting the diode's pins would damage the LD itself, the driver yes but as the current isnt flowing through the diode so it should be ok? But it sounds like it's LEDd, maybe the currant was too high?
 
Eudaimonium

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ultimatekaiser said:
It's an Lm 1117 driver and I'm going to use two 3.7v batteries to power it. The diode needs 2.5V and around 90-100mA I'm at work ATM so I can't take pics.
Click to expand...

What is the value of the resistance on your Voltage reference line?

In other words, what is between your LM's OUT and ADJ pins?
 
Leodahsan

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NKO29 said:
TBH i dont actually think shorting the diode's pins would damage the LD itself, the driver yes but as the current isnt flowing through the diode so it should be ok? But it sounds like it's LEDd, maybe the currant was too high?
Click to expand...

Yes it does. Even if you direct drive a diode and short the battery, it will go LED.

I founded out that a 100nF ceramic capacitor soldered close to the diode protect it from spikes and in an accidental short, it will save the diode.
 
NKO29

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Leodahsan said:
Yes it does. Even if you direct drive a diode and short the battery, it will go LED.

I founded out that a 100nF ceramic capacitor soldered close to the diode protect it from spikes and in an accidental short, it will save the diode.
Click to expand...

Direct driving kills the diode from over current... Having regulated current bypass the LD (shorting across the pins) should mean that the LD will be UN-Harmed as it's DC voltage and cannot go back to the source +? Might be worth testing on one of my shitty LDs pulled from dvd drives :thinking:
 
ultimatekaiser

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I'll take pics when I get home. It's one of jufran88s linear lm1117 drivers and is allowing about 109mA through. The diode takes about 2.5V @ 90mA. And I'm using one of mrcrouse's hosts. How do you think I should have it wired?

Strangely if I wire it LD cathode PIN to LD- & use the photodiode anode it lights, but on contact with the case it goes out. (Case negative) as it's shorting out. If I use the LD anode (com pin) it doesn't seem to work
 
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ARG

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I'm sorry for your loss :(

I remember when my first diode bit the dust, it hurt.
 
ultimatekaiser

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Sorry edited and yeah it does :/ I don't wanna kill another.

Edit: I've ordered a few more drivers and supplies, when they get here i'll reattempt this build. hopefully I can get it fully right this time!
 
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Leodahsan

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NKO29 said:
Direct driving kills the diode from over current... Having regulated current bypass the LD (shorting across the pins) should mean that the LD will be UN-Harmed as it's DC voltage and cannot go back to the source +? Might be worth testing on one of my shitty LDs pulled from dvd drives :thinking:
Click to expand...

Direct driving will only kill the diode if you source enough voltage, so a high If will flow when the diode is hot and bang :)

If you direct drive a a140 on a li-ion, it will barely output 500mW.

I mean that, if you short the LD during operation, and it does not have the appropriate capacitor on its pins (most drivers have) it will die from the spike. Ive seen it happen.


I direct drove a 16x dvd burner diode, with a 10ohm resistor. When I accidentally shorted the leads, it gone LED.

I did the same with another diode, but put a 100nF capacitor soldered behind it (VERY close). I could not kill it from shorting the source.
 
WizardG

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"I direct drove a 16x dvd burner diode, with a 10ohm resistor. When I accidentally shorted the leads, it gone LED."

Was that by any chance a wirewound 10 ohm resistor? That would be the only way the scenario you describe would make sense to me. i.e.-x amount of current flowing through resistor and diode then the diode is shorted causing excess current to flow through the resistor (which if it's a WW resistor is also an inductor) then when the short across the diode is removed the inductive nature of WW resistors results in a spike of current through the diode.
 
NKO29

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Leodahsan said:
Direct driving will only kill the diode if you source enough voltage, so a high If will flow when the diode is hot and bang :)

If you direct drive a a140 on a li-ion, it will barely output 500mW.

I mean that, if you short the LD during operation, and it does not have the appropriate capacitor on its pins (most drivers have) it will die from the spike. Ive seen it happen.


I direct drove a 16x dvd burner diode, with a 10ohm resistor. When I accidentally shorted the leads, it gone LED.

I did the same with another diode, but put a 100nF capacitor soldered behind it (VERY close). I could not kill it from shorting the source.
Click to expand...
That makes sense, i was talking about when it's hooked up to a driver :) I have actually accidentally shorted LD + & - and they've been fine, but all of DTR's drivers are good quality and have caps so they saved my diodes i guess :D
 
ultimatekaiser

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well the driver has a resistor and a couple capacitors on it, but not sure of the capacitive value. the resistor says 100 on it and is black
 
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