Author Topic: Need to fuse LED's  (Read 6798 times)

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mixerman

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Need to fuse LED's
« on: June 24, 2011, 03:59:20 PM »
Can some one help with what I need to protect my 24Guage wires when installed into a 12v system.(car battery) I don't know what I need amp wise but I would think it would be smaller than anything in automotive. I wouldent want these wires to turn into some sorta hot knife if grounded out!

The purpose of the LED is simple! When power is present the LED burns, if its interuted its off.3395-0

ETech

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Re: Need to fuse LED's
« Reply #1 on: June 24, 2011, 04:16:05 PM »
Fuse 24 ga wire with a 1 amp fuse.
The fuse would be to protect the wireing.
Connect the fuse directly between the power source and the 24 AWG wiring.

other gauges:
22 AWG 3 amp fuse.
20 AWG 5 amp fuse.
18 AWG 7.5 amp fuse.
16 AWG 10 amp fuse.
14 AWG 15 amp fuse.

24 AWG may be to small mechanically for auto use (too easy to break).
I would use 20 or 22 AWG for the strenght of the wire.
You wouldn't need to for current capacity for running low current LEDs.

You can allways use a smaller fuse with a higher current carring wire.

ETech


rossw

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Re: Need to fuse LED's
« Reply #2 on: June 24, 2011, 04:53:28 PM »
I wouldent want these wires to turn into some sorta hot knife if grounded out!

You've indicated you want 20mA for the LED, and a 12V battery.
While "unconventional", you could always put the resistor right at the battery rather than at the LED.
A 470 ohm resistor will limit LED current to about 21mA with the added advantage that even if there were a dead short somewhere along your wiring, the current will be limited to 25mA - nowhere near enough to get hot or burn.

500 ohms will limit LED current to 20mA (at your stated 12V, with 2V drop across the LED). Higher resistances will lower LED current further, and also (obviously) limit short current even more.

A circuit so arranged is pretty safe even without a fuse because you've limited the current so much. Note, the resistor will need to be half-watt or better.

DanG

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Re: Need to fuse LED's
« Reply #3 on: June 24, 2011, 05:05:49 PM »
and... stranded wire in a vehicle, solid core wire will harden and become fragile anywhere it gets repeatedly flexed...

mixerman

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Re: Need to fuse LED's
« Reply #4 on: June 24, 2011, 06:18:46 PM »
Thanks guys!  I wished I would have asked afew days ago, I do have a 1 amp fuse for this one. I allready soldered it up. I guess I can make up another, I can use this one for in the driveway rather then in the car.

  My car drops dead!!! It only does it when it want to ! I want to find out where its dropping dead! It allways re-starts!! There are never any codes!!!

The board I placed the LED's on needs to be protected some way! Can I use hot glue to do this?  This is the first time I have ever done this, had to start somewhere!

I like the fuseless design (Pict)

« Last Edit: June 24, 2011, 06:41:31 PM by DanG »