How to select a fuse

Discussion in 'General Electronics Chat' started by copucopu, Oct 2, 2014.

  1. copucopu

    Thread Starter New Member

    May 26, 2014
    I need a Fuse for my LED light. It operates at a range 10-18V and the current cannot exceed 160mA.
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
    the fuse will not set the current for your led. and low current fuses have fairly high resistance, which has to be figured in to the bias for the led. I use .01 amp fuses for 50 ohm bolometers when mesuring low level rf power, since they have a resistance of 50 ohms.
  3. copucopu

    Thread Starter New Member

    May 26, 2014
    So what solution do you recomend?
  4. MrChips


    Oct 2, 2009
    The purpose of the fuse is not necessarily to protect components from damage but to prevent catastrophic disaster in the event of a component failure or malfunction. Generally speaking, the amperage rating of the fuse will exceed the normal operating current while taking current surges into account. There is no set rule on how much headroom to provide and anywhere from 50% to 100% over-current is acceptable depending on the application and level of current and voltages.

    Bare in mind that fuses will have wide tolerances which are also very dependent on ambient temperature. A fuse is not designed to limit the current driving LEDs. Use a constant current source for such applications.
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
    Fuses serve to prevent a fire in the event that the device fails; not to protect the device from failing...
  6. #12


    Nov 30, 2010
    Here's a way:
  7. Lestraveled

    Well-Known Member

    May 19, 2014
    Fuses and circuit breakers are generally sized to protect the wiring, not the device.

    If your LED draws too much current it would be from either the LED shorted or you applied too much voltage. Protect against these conditions.
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    Must have specifications/part number,etc.. on the LED?
    Is the 10-18V the forward voltage rating (Vf)?

    There are a few ways to make a "constant current" power supply for use with LEDs that do not already have some form of current limiting built into them.. A fuse is NOT one of those ways ever.
    #12 posts one above using am LM317 in constant current mode..
    Just using a resistor is another..
    Using an LED driver IC or device is another..
    Or your "LED" as you call it may already have current limiting built in but we don't know and shouldn't assume with you.

    Without knowing the details of your LED we cannot direct you to the proper solution.