diode

[kdam36]

how do i test a diode?
i`v got a dead red laser and i want to put another diode out of a dvd writer into it but i dont know how to test for polarity.
i`v got a fluke test meter that i kinds know how to use but i`v never tested a diode before

thanks
al.

 

[Ashton]

Get a PSU set to low amp (preverably ~ 15ma, that shoudl be safe for even a pointer), and low voltage (1.6v IIRC), then touch the negative lead to the casing and the positive lead to each leg of the diode that's not atached to teh case, one is a feedback pin, will give you nothing, the other will activate the diode. (BE SURE IT IS NOT POINTED AT YOUR EYES OR A REFLECTIVE SURFACE!) After that, keep the red on the positive and use teh black to test the two other pins to find the negative.

Do not try to use the negative on a diode leg initially as if you get +/- reverse you kill the diode, the casing is usually negative, so this works 99/100 times.

 

[pseudonomen137]

Might want to try using the ohmmeter and finding out what seems to be a reasonable path, but I'm not sure if the power used to test the resistance can kill the diode or not. My guess would be not but I really don't know. As Ashton was mentioning, use the case as that is normally one of the connections, and then try the different pins to the diode. I wouldn't suggest doing that with a power supply though as you might blow something out that way. I have a feeling I shouldn't be saying this, but you normally can apply voltage in reverse without harming the diode, you just wont get any output and should quickly remove the leads to be safe.

 

[Aseras]

all red diodes for at least dvd burners are 3 legged. bottom middle pin is connected directly to the casing and is your ground pin. then you will have two pins above it on the same level. the right pin is your + lead.. the other pin is for the photodiode and is usually unused.

just use the casing with an alligator clip as gorund and add a 2.4-3 volt load to the pins. one will make it light the other one wont. try to keep the current to the diode below 300ma or you risk the diode although most red diodes can take direct battery current for quite a while ( i've even used 3 AA batteries direct to one red diode for 4.5 volts and 7500ma.. it worked for quite a while and was well over 300mw for the couple weeks it lasted ) i got lucky

 

[Ashton]

( i've even used 3 AA batteries direct to one red diode for 4.5 volts and 7500ma.. it worked for quite a while and was well over 300mw for the couple weeks it lasted ) i got lucky

mine lasted <1 week. If you want to count the on-time, it as probablt <5min and I only used 2AA batteries!

 

[pseudonomen137]

all red diodes for at least dvd burners are 3 legged. bottom middle pin is connected directly to the casing and is your ground pin. then you will have two pins above it on the same level. the right pin is your + lead.. the other pin is for the photodiode and is usually unused.

just use the casing with an alligator clip as gorund and add a 2.4-3 volt load to the pins. one will make it light the other one wont. try to keep the current to the diode below 300ma or you risk the diode although most red diodes can take direct battery current for quite a while ( i've even used 3 AA batteries direct to one red diode for 4.5 volts and 7500ma.. it worked for quite a while and was well over 300mw for the couple weeks it lasted ) i got lucky

I'm not sure if the DVD diodes are standardized or not, but I would be careful about assuming which pin is which. Different diodes have different configurations and case polarities, and I've even seen some 4-pin can diodes.