Can I test LDs with a diode tester?

Hi to everyone at LPF! I was wondering if I could test a 16x DVD burner diode with the diode tester function on my crappy Nexxtech digital multimeter. I mean, it's a diode, right?

When I use the diode tester on LEDs, they glow dimly and it gives me a forward voltage reading (I think...) So would I be able to cause a 200mW LD to lase at all? And maybe make sure of the polarity/whether it works or not? Or would it break my laser diode?

you will be able to get most diodes to light up, the problem is that I think most multimeters only put out around 3v for diode testing. This will be enough to light up your red diode just to verify it actually works. But, it probably wont light it up enough to tell you if its dead or not. Basically it will just tell you that the tiny wires inside aren't broken, and you'll be able to figure out the polarity. With the 405nm diodes, which require a higher voltage, it may not light up at all.

I tried and the multimeter showed a number starting with 1 a couple of times briefly. The diode did not 'lase' or light up. I think my multimeter might be defective, I have noticed a couple of measurements don't work sometimes. I hope my LD isn't dead - It has never been powered until now [using the multimeter.]

Is there any other way I can safely check the LD? I don't have a driver, is there a simple one I could construct out of spare electronics parts? (650nm, ~200mW)

The only other way I could think of would be to connect a wire from a 9V battery to your diode, but that would kill it almost instantly.

iewed said:

The only other way I could think of would be to connect a wire from a 9V battery to your diode, but that would kill it almost instantly.

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Yeah dont do this. A way you can test just to make sure is build a driver. Really this is the only safe way to know you wont kill it. You can build a really simply driver with radio shack parts. You need an LM317 positive regulator, a capacitor (somewhere around 10v just make sure its more than the input voltage... capacitance isn't really important as long as its above a few uf. Most people here use 47uf, just because thats what was used in the original post about building your own driver), and a few resistors or a potentiometer or both. I have the schematic if you want me to post it. You can build the thing for less than $5

Well if you have a regulated DC power supply , like the ones you would use in a lab at school you could use that, thats what I use. I just put it at the correct voltage and put the current to full (2.19A ;D) and hook it up, becuase the way mines is built it doesnt send 2A shooting into the diode, it supplies the diode with whatever current it needs, say 200mA.

But if you aren't sure, just use a driver, they are easy to build.

Diachi

I have an LM317 on a breakout board. I noticed that when I turn the trimpot on the board the voltage goes up or down by .01 at a time. Is this what I need? It has 3 pins: VIN, GND, and VOUT. It's made of SMD components - there is a diode, two caps, a row of 4 resistors, and the LM317 with "317H 4238E" on it.

Oh yeah and I can't measure current - my multimeter shows 0 on everything.

Oakwhiz said:

Oh yeah and I can't measure current - my multimeter shows 0 on everything.

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Sounds like you blew the internal fuse. If you're feeling risky or you just dont care about the meter, take it apart and jumper the fuse connection with a wire.