Fuse keeps tripping.
Fuse keeps tripping.
(OP)
I have a motorcycle that I'm trying to put 6 LEDs on. The battery is a 9V wet cell and I'm trying to route the LEDs off the headlight circuit which uses a 10A fuse. I'm trying to use 20mA LEDs. Can anyone please tell me what I need to do to make this work? I was hoping to just route it off the positive end of the headlight bulb and connect the LEDs in series all the way to the negative end of the bulb. I figured there would be enough power to make both work. Thank you.





RE: Fuse keeps tripping.
RE: Fuse keeps tripping.
RE: Fuse keeps tripping.
RE: Fuse keeps tripping.
More generically, the formula is (Source Voltage - LED DROP)/(Desired LED Current).
The source is nominally 12V but really 13.6V. The voltage drop of a single LED is 1.6V. Therefore, if each led were wired with its own current limit resistor, the formula works out to (13.6 - 1.6)/(.02) ohms or about 600 ohms. 680 ohms is the nearest standard value higher (never go lower).However, to reduce current draw, I suggest wiring the LEDS into two groups of 3 in series. This would then require only 2 resistors of (13.6 - 4.8)/(.02) ohms or 440 ohms. 470 ohms is the nearest higher value. A 1/2W would be fine. I do not suggest putting all 6 in series and using a single resistor as the brightness would fluctuate too much with varying RPM of the bike.
RE: Fuse keeps tripping.
RE: Fuse keeps tripping.