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Fuses?

Wolfman29

Wolfman29

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So I went to RadioShack the other day and picked up some fuses for testing out drivers and diodes. But then it hit me - why haven't we ever put fuses into our drivers as a safety precaution against high-current draw?

Maybe because it is impractical? Do they make fuses for high-current draws small enough to fit on our driver boards? (I am talking SMDs here.)

It *would* be an excellent safety feature if you are using a previously untested driver (besides your normal testload) to give extra safety to an expensive diode.

Anyway, just a thought. Anyone have anything to say?
 





lasersbee

lasersbee

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Because a Laser Diode will blow way before a Fuse will...
Regular fuses are just not fast enough.

Jerry
 
Coherent Light

Coherent Light

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You can get SMD fuses small enough, but the Diode would blow quicker than even a fast-blo fuse if it was sized close to the diodes limit IMO.

Jerry beat Me....
 
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Cyparagon

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Laser diodes generally die from overheating or static discharge. They don't often die from over-current unless you hooked something up wrong, or you're talking about the people that like to drive their 445s at ridiculous levels like 1.8A :rolleyes: A fuse won't help you there.
 
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Bionic-Badger

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I think we'd need fuses with wires smaller than the bonding wires on the laser diodes. Better to have some sort of capacitor or something that can just eat the charge.
 
Flaminpyro

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There are fuses this small but as the others said I don't think this will help, on the other hand it couldn't hurt either ;)

the device marked 242 is a resistor the fuse is the one marked FP, FlaminPyro :D
Peace All...
 
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rhd

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In theory, if you were building something like an HL63133DG-based pointer, where the diode is $200 and you're nervous about killing it, you could:

- Find a cheap IR diode with roughly the same current death range. I think something like a 300mA IR would work with the diode I mentioned. Put it in series with your expensive diode, arctic silver it to the inside somewhere for heatsinking, make sure your driver can handle the voltage, and voila, you have a fuse.

I don't think this is a very good idea, nor a very useful one, but my imagination asked me to point it out.
 
Trevor

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rhd said:
In theory, if you were building something like an HL63133DG-based pointer, where the diode is $200 and you're nervous about killing it, you could:

- Find a cheap IR diode with roughly the same current death range. I think something like a 300mA IR would work with the diode I mentioned. Put it in series with your expensive diode, arctic silver it to the inside somewhere for heatsinking, make sure your driver can handle the voltage, and voila, you have a fuse.

I don't think this is a very good idea, nor a very useful one, but my imagination asked me to point it out.
Click to expand...

You'd have to melt the bond wires for that to work. At that point, the diode you wanted to save probably would have LED'd. ><

-Trevor
 
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Flaminpyro

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So dose this mean there are no realy fast fuses ?
like
50 microsecond type,

only in space ships I know

cuz they $300.00 each
 
rhd

rhd

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Trevor said:
You'd have to melt the bond wires for that to work. At that point, the diode you wanted to save probably would have LED'd. ><

-Trevor
Click to expand...

Yep... makes sense - see, I knew it wasn't a good idea ;)
 
Cyparagon

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rhd said:
Find a cheap IR diode...
Click to expand...

As pointed out, the main problem is they don't generally fail open. They undergo what's called catastrophic optical damage (COD) aka "ELL-EE-DEEing" So a huge current spike would likely kill them both.
 
Flaminpyro

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Yes I can see the diode can conduct or turn on very fast so the fuse would need to work so fast it isn't practical to make one.
and as you said COD would probly still happen when the fuse blows.

Capacitors we need more Capacitors...
 
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