Testing a circuit without risking NEW diode.

[Kenom]

Those of us that have killed more than a diode or two know that these things are as precious as gold. We don't wanna throw a diode into a circuit we've built and risk the brand new diode so I've thrown this up here as a reminder that even a 1mw laser diode makes a great dummy load for testing your circuits. So if you have toasted a diode and it's still capable of lasing (although not above 1mw) use it to test the current and voltage of a circuit before you throw that brand new one in and destroy it!

 

[Hemlock_Mike]

Another option is to use one of the Cree style stars as a load. Anyone who has modded a flashlight should have one. Many of them work around 350 mA. They do get rather warm.

Mike

 

[o_DEATH_ANG3L_o]

Excellent point guys.

 

[Benm]

How is a 1 mW diode a good load for testing driver circuits? If i hook one up to a 200 mA current source, i'm quite sure it will be blown up instantly if the current source is doing its job.

Those cree stars are a much better option (as is any power LED). Only thing is that the white ones take a bit more voltage than the average LD, so they are only suitable dummyloads for drivers with voltage to spare.

 

[Kenom]

I'm sayin if you've turned a nice gb diode into an led instead of tossing it in the trash, use it to test a driver circuit instead of trashin it. that way if it's too much then you fry it completely and havn't wasted a good diode.

 

[Hemlock_Mike]

Kenom is right here insofar as even if a <5mW LD or GB diode goes LED, It's still a load.
Save your good LD's until your driver circuit is tested and under control.
Simple resistive loads do not have the same non-linear characteristics as a diode.

Mike

 

[o_DEATH_ANG3L_o]

Keep in mind too that when an LD has turned into an LED, and you run current through it, it heats up insanely fast. Even at 150 mA it gets quite toasty really fast. But Benm as everyone said, it does make a good load for a circuit test.

 

[Benm]

Didnt see you ment a fried power diode - though you'd just use one of those $1 low power diodes.

A fried GB diode will work as long as only its optics are fried, but a 5 mW diode will not be a good load. The will have a higher voltage drop for a given current, so they might mislead you with badly regulated drivers.

If you don't account for voltage drop, you might as well use a crowbar as a dummy. It'll still take 200 mA or whatever you set the current source too, only with negible voltage drop

 

[chimo]

For the GB LDs, if you want to check using a pure resistive load, try using a resistror around 14ohms. Most of the GB LDs I have tested come in around 2.85V when driben at around 200mA. This will not be ideal, but will give you an idea if your driver is within range.

Paul

 

[CHP]

My GB LD hasn't arrived yet, but you could try 3 or 4 1N4001 diodes in series to simulate a LD load.

 

[Benm]

Those make excellent dummies indeed. Personally i prefer the power led when i'm thinkering with current drivers since they provide optical feedback when tweaking things, but electrically 4 1n400x diodes are better dummies.

 

[mw1111]

could this little LED i have work as a dummy load? it came out of a cheapy little flashlight, so idk what kind of resistance it has, or anything like that