350, 375 400ma quick blow fuse

Anyone know where to buy one? Ratshack only has 3.0 and 3.14 then it jumps to .5 amps

I'm looking for a fuse that will blow before my Red 1 Watt Star-O's do.

The idea behind a fuse is to blow when the current exceeds what is healthy for the device.

Example 1;

A car headlight rated 25 watts (about 2 amps at 12 volts) will have a wire that can handle 10 amps. A 7 amp fuse (70% of the max rating of the wire) would be called for.


Example 2;

A luxeon is designed to handle 375 ma. A look at the specs may show that it can handle .5 amps for 300 hours before it degrades. It may handle 2 amps for 1 minute. 70% of .5 is about .375, so a .5 amp fuse would protect you from a situation where the current was more than a little elevated.

Experience will teach you that current or voltage is seldom just a little bit out of range. When components short out they can put all sorts of ugly voltage where you didn't want it.

Daniel


Murphy's law of fuses; A 20 dollar component will protect a 10 cent fuse by blowing first.

lol about Murphy's law...

Im' using a current limiting resistor, And my laste experiences with them are that they fry out quick and sudden, So you think a 500ma fuse would work then?

I have the LM317T programed to about 340 something ma.

Im running a 1 amp fuse on a second circuit for the 3 watt luxeons that are running 960 something amps and it seems to be working great.

My last experience with no fues was the sudden death of an LM317HVT and it took a red with it, then I managed to short out a 317T (my fault) and it took BOTH my LuxIII's with it...This time im using fuses!

you sure a red 1 watt star won't fry at 500ma? I know they can't take as much as the other colors. But if the LM31tT does fry there will an instant 3 or so amps to my lights.

My post included estimates from memory. You should check the datasheets to be sure.

According to Lumileds datasheet (ds23.pdf) the maximum pulsed current is 550ma with average current of 385ma for the red 1 watt. I read this to mean that a 1 watt will continuously handle up to 550 ma pulses without any damage of any kind IF the average current is 350ma. So a quick spike of 1 amp will trip the fuse before the average exceeds 350 by an appreciable amount.

Where this gets interesting is that one can use a PWM controller to get more light with less power by figuring out what the decay is of the phosphor. If it comes to full brightness in 4/100 of a second and dims to 90% after 1/100 second, you could run it at 500 ma for 4/100 second then cut the power for 1/100. The end result is a a light almost as bright as running at 500ma, but using the same power as 350 ma. These figures are reasonable, but not verified in any way.

Daniel




Daniel

[ QUOTE ]
gadget_lover said:
My post included estimates from memory. You should check the datasheets to be sure.

According to Lumileds datasheet (ds23.pdf) the maximum pulsed current is 550ma with average current of 385ma for the red 1 watt. I read this to mean that a 1 watt will continuously handle up to 550 ma pulses without any damage of any kind IF the average current is 350ma. So a quick spike of 1 amp will trip the fuse before the average exceeds 350 by an appreciable amount.

Where this gets interesting is that one can use a PWM controller to get more light with less power by figuring out what the decay is of the phosphor. If it comes to full brightness in 4/100 of a second and dims to 90% after 1/100 second, you could run it at 500 ma for 4/100 second then cut the power for 1/100. The end result is a a light almost as bright as running at 500ma, but using the same power as 350 ma. These figures are reasonable, but not verified in any way.

Daniel




Daniel

[/ QUOTE ]

Wow dude! Thats some good info, I think ill pickup a 500ma fuse then. to be safe. I don't need these things any brighter though, im using them for a taillight lol! Don't want to blind anyone, the NX-05 optics are perfect for this application.

Thanks for the input, I'll put a 500ma fast-blow inline fuse on before I get finish it up.

But that's not what 'maximum pulse current is 550 mA' means. Strangely, it means 'don't ever run more than 550 mA, even for a very short time'.

And that's not how fuses work. They heat up and die (melt) from high current, same as LEDs do. Only the LED is faster. Murphy is right.

Typical ratings are 'hold rating (enclosed) for ever, open in ten seconds with 100% overload, 1 second with 500%, .01 second with ten times....'. There is mass there, time is involved. The bond wire on the diode and the crystal itself have a clear advantage in the race to the death.

In sort a 500 mA fuse will not offer any real long or short term protection, save your money.

Doug Owen

you have to be kidding right? I just bought the setup last night...So a 500ma inline fast blow buse wont do any good if my circuit shorts out? Damn more wasted $$$...

Whhat the hell kind of fuse SHOULD I put in there...
I think the 1 amp fuse on the Lux III should save it since the LED can take more than 1 amp for a short period....But I was planning to use the 500ma fuse for the Star-O...Your saying this will not work at all?

Well I already spliced teh fuses in, so they won't do anything?

Someone has to know!

What the hell can I use if I can't use a fuse?

[ QUOTE ]
Well I already spliced teh fuses in, so they won't do anything?

Someone has to know!

What the hell can I use if I can't use a fuse?

[/ QUOTE ]
I believe that the other Doug is correct that the LED will likely go before the fuse. You are using a current regulator based on an LM317. This should be very reliable protection. It should be very rare to have the LM317 failure that you experienced.

[ QUOTE ]
[ QUOTE ]
Well I already spliced teh fuses in, so they won't do anything?

Someone has to know!

What the hell can I use if I can't use a fuse?

[/ QUOTE ]
I believe that the other Doug is correct that the LED will likely go before the fuse. You are using a current regulator based on an LM317. This should be very reliable protection. It should be very rare to have the LM317 failure that you experienced.

[/ QUOTE ]

I have had 2 of them fail out of 4....I already bought the fuses, it's a tiny dinky strand of wire..Since I already bought and opened everything I might as well install them anyways right?

[ QUOTE ]
Well I already spliced teh fuses in, so they won't do anything?

Someone has to know!

What the hell can I use if I can't use a fuse?

[/ QUOTE ]

Doug already explained how fuses work - they WON'T protect the Luxeon. Your energy would be better directed at making the regulator circuit reliable.

I assume this is still your ATV project...

george.

[quoteI have had 2 of them fail out of 4....I already bought the fuses, it's a tiny dinky strand of wire..Since I already bought and opened everything I might as well install them anyways right?

[/ QUOTE ]

Then you still have the problem I mentioned in your original thread. Your ATV is probably generating some pretty nasty spikes on it's electical system since you have no battery iirc. You need to put some stuff in the front end of your regulator circuit to protect the 317.

george.

Yea, but I looked into batteries and its WAY to complicated...For example, As im driving im charging the batteries, but at what rate? Who knows! it depends on the RPM's Then the other problem, I could overcharge the batteries and kill some expensive batteries.

I'm using a capacitor to stabalize the power flux in the AC to DC design...

So I should remove both fuses I purchased? There is not point in even using the a AMP fuse? I probably only hit over 1 amp at high RPMs mid-full throttle...I figured the fuse would blow at an amp so im underdriving the lights to keep the temps down...

your suggesting I remove the inline Quick Blow fuse I already added? The wire is so small int he 1/2 amp fuse it looks like a light bulb filiment strand...It still will not work?

So I guess I should cut the fuses out of the circuit and stick them in my "Junk that I will never use drawer"???

I don't mind the battery idea, but I believe I would have to design a peak charger to go with it...This is adding lots of weight complexity and size to the overall design..

Do you know how to build a peak charger that runs on variable AC? I sure as hell don't /ubbthreads/images/graemlins/frown.gif

Thanks for the help and support guys! I guess I wasted my $$..I wish I had that $12 right now so I could eat some real food...Guess its PB & J Tonight /ubbthreads/images/graemlins/broke.gif

Let me know if I should remove both the 1 amp fuse for the Lux III and .5 amp fuse for the Star-O.

PS. the spikes are regulated by a voltage regulator priot to the circuit, it protect the whole electrical system from exceeding 14.4V...14.4V is hard to hit, near full throttle im usually at 12.

If you have fuses in, I wouldn't pull them.

As far as bitty goes, don't bet against LED bond wires. They may be gold, but it's only 'cuz they're so small (in diameter) that we can afford to use gold.. No bigger than it takes to carry the maximum current necessary (which we'll call maximum peak current) of course. Clue there.....

The 'fast blow' fuse (I think) you're using is spec'd to blow within an hour at 130%, 5 seconds at 200%. A serious fraction of a second at short second currents (say 10 amps?). By then the LED will be scrap.

On the other end, it would be easy to 'cook off' the LED at several times the expected current without blowing the fuse, either should the regulator fail.

As Freewheelin' Franklin might say, "LEDs make better fuses than fuses make LEDs".

If the topic (before I came into it) is 'How do I run the lights on my motorpickle?', let's talk MOVs......

Doug Owen

well I'll leave the 1 amp fuse alone then, But I don't think I can return the other one. I had opened it just hours before I caught the post that said it would not work...In fact I was just getting ready to go install the 500ma one...I guess I'll just keep it in my junk drawer since there is no practical use for it..I'll have to run the circuit without a fusable link then I guess /ubbthreads/images/graemlins/frown.gif