Blue ray diode issue

[FlightLevel350]

I have a PHR blue ray diode, but I can't get it to output very much light, even when held up to something flourescent. I measured the current to the diode, and although the driver I am using is limited to 125mA short circuit, I am getting only 50mA through the diode. The voltage to the diode is around 5-6 volts, but across the diode its only about 4.45. Is this a problem with the diode, or do I need to get a different driver? The current driver is a simple adjustable current output

 

[Droyd]

voltage should be 7-12

 

[FlightLevel350]

To the diode, or to the driver? Or does it not matter?

 

[rog8811]

To the diode, or to the driver? Or does it not matter?

What driver are you using?

LM317 you need 9v
Rkcstr you need 7.2v
Lavedrive input voltage ok as is

Regards rog8811
[edit]When you say 125ma short circuit, how did you test it?[/edit]

 

[FlightLevel350]

I'm using a LM317. The short circuit current was measured across the leads from the driver with no load, to determine the threshold current value. Actual current (through the diode) was 45 mA

 

[rog8811]

The short circuit current was measured across the leads from the driver with no load, to determine the threshold current value

You need to test it with a dummy load equivalent to the LD and you will need 9v to run it.

Regards rog8811

 

[FlightLevel350]

Is there anything special about that type of diode, or do normal diodes work just as well?

 

[Spoz]

Any 1N400x series diode will work.

 

[Fariniac]

Ok, silly electronics question here. Given that the 1n400x series diodes are basically used to prevent amperage flowing in the wrong direction by acting as a very low ohm resister in one direction and a high in the other, why would you need to put 6 of them in series?

It's probably a daft question for you guys, but it's something I have never understood.

Cheers, Fariniac

 

[rog8811]

Each diode gives a voltage drop across it, usually around 0.7v so 6 X 0.7 = 4.2v which is close to the voltage drop across the LD.

Regards rog8811

 

[Fariniac]

ahh, now it makes sense. I have only ever used them to make a bridge rectifier, never for voltage drop. A lot of circuits suddenly make more sense..lol

Cheers