Help with fuse - Overclock.net

**Boris4ka** · 10-01-09

I made this a while ago: http://www.overclock.net/other-hardw...led-array.html

and now I want to get a fuse for it, but have no idea where to start or what to do. My light shorted and started smoking heavily, and now I'm worried if it happens again the battery might blow up in my face. So please help me with the numbers, I have no idea what I need.

Raptor_Jesus · 10-01-09

Not sure if a fuse is necessary. Did you add a resistor in there for the LEDs?

**Boris4ka** · 10-01-09

Quote:

Originally Posted by Raptor_Jesus

Not sure if a fuse is necessary. Did you add a resistor in there for the LEDs?

Yes, there are 25 resistors, 1 for each 2 LED's. But what does that have to do with a fuse? There was a short, and a resistor fried because of it. I want a fuse to protect the battery from shorts.

DesertRat · 10-01-09

How many amps @ how many volts does it draw?

**Boris4ka** · 10-01-09

Quote:

Originally Posted by DesertRat

How many amps @ how many volts does it draw?

7.2V, no idea how many amps

Do I need to calculate it somehow?

M1 Abrams · 10-01-09

ok bear with me on this...
get an inline fuse holder>
http://www.radioshack.com/product/in...ductId=2102786
connect in series on power line.
I used these on an amplifier & connected it to the collector of output transistor to protect my output transistor from distortion (DC) in an ac cicuit.
This will work on DC also.
just get a small fuse say .10 amp and turn on lights...if it blows put in a .20amp etc...till you get it to NOT blow. Fuses are cheap in price.
This fuse will be just above the current draw and any short will open the fuse.
get quick blow fuses at any auto store.

edit>
you can roughly calculate current by adding the watts of all lights & you already have the volts.
ExI=watts (volts times current =watts)
watts divided by voltage =current draw

**Boris4ka** · 10-01-09

If you click on the link in my first post, you'll see the specs for each LED (I'm using 50 of them). I'm still confused on how to get the watts. Do I need to do 0.2 * 3.4V, then x50? That gives 34 watts and that sounds like too much.

M1 Abrams · 10-01-09

ok you have 7.2 volts & 50 led's
Lets say that each led burns 1/4 watt
so thats roughly 12 +/- watts total.

now the 1/4 watt each is a guess**
so the other way to do this effectivly is to buy the smallest amp fuse and put it in fuse holder inline & it will prob blow(good that it does)
now increase the size(amps of the next fuse) & try it again....
so you might end up with a .25 amp fuse that allows your lights to work but, if any short happens it will blow.

**Boris4ka** · 10-01-09

I don't want to buy a bunch of fuses to experiment this way, at almost $3 each it's going to be too much for a small project like this. Can I find out how many watts each led uses?

Quote:

- Forward Voltage 3.2V MIN, 3.4V MAX (20mA)
- Reverse current: 10u (VR=5V)
- Power dissipation: 60mW
- Luminous Intension 14000 mcd MIN, 16000 mcd MAX
- Peak Forward Current: 100mA
- Recommend Forward Current 20mA
- Electrostatic Discharge: 2000V

Is it 60mW? How many W is that?

M1 Abrams · 10-01-09

Quote:

Originally Posted by Boris4ka

I don't want to buy a bunch of fuses to experiment this way, at almost $3 each it's going to be too much for a small project like this. Can I find out how many watts each led uses?

Is it 60mW? How many W is that?

not sure if thats mili or micro(mW)

a mili watt is one thousanth of a watt

micro is one millionth of a watt

edit> im working on this brb

10-01-09	#6 (permalink)
M1 Abrams Overclocker Join Date: Apr 2009 Posts: 642 Rep: 59 Unique Rep: 51 Trader Rating: 0	ok bear with me on this... get an inline fuse holder> http://www.radioshack.com/product/in...ductId=2102786 connect in series on power line. I used these on an amplifier & connected it to the collector of output transistor to protect my output transistor from distortion (DC) in an ac cicuit. This will work on DC also. just get a small fuse say .10 amp and turn on lights...if it blows put in a .20amp etc...till you get it to NOT blow. Fuses are cheap in price. This fuse will be just above the current draw and any short will open the fuse. get quick blow fuses at any auto store. edit> you can roughly calculate current by adding the watts of all lights & you already have the volts. ExI=watts (volts times current =watts) watts divided by voltage =current draw Last edited by M1 Abrams : 10-01-09 at 08:49 PM

10-01-09	#8 (permalink)
M1 Abrams Overclocker Join Date: Apr 2009 Posts: 642 Rep: 59 Unique Rep: 51 Trader Rating: 0	ok you have 7.2 volts & 50 led's Lets say that each led burns 1/4 watt so thats roughly 12 +/- watts total. now the 1/4 watt each is a guess** so the other way to do this effectivly is to buy the smallest amp fuse and put it in fuse holder inline & it will prob blow(good that it does) now increase the size(amps of the next fuse) & try it again.... so you might end up with a .25 amp fuse that allows your lights to work but, if any short happens it will blow. Last edited by M1 Abrams : 10-01-09 at 09:15 PM

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Help with fuse

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