reduce led current draw
reduce led current draw
(OP)
Someone has yanked my alarm LED from my motorcycle.
I called the alarm manufacturer and they told me that alarm system is discontinued but that I could go to Radio Shack and buy any red LED at 12V with less than 5 mA draw. The smallest drawing LED I could find with that voltage was a 15 mA and so I picked that one up and installed it on my motorcycle: Great bright red light, more than I really needed but I figured it's an alarm LED, the brighter the better but sure enough the first time I did not use my motorcycle for 3 days in a row, I found the battery almost dead.
What should I do to reduce the current drawing to <5 mA...? I am willing to loose a lil brightness, someone told me 1K resistor in series, someone told me a few diodes in series.... I am confused....
I called the alarm manufacturer and they told me that alarm system is discontinued but that I could go to Radio Shack and buy any red LED at 12V with less than 5 mA draw. The smallest drawing LED I could find with that voltage was a 15 mA and so I picked that one up and installed it on my motorcycle: Great bright red light, more than I really needed but I figured it's an alarm LED, the brighter the better but sure enough the first time I did not use my motorcycle for 3 days in a row, I found the battery almost dead.
What should I do to reduce the current drawing to <5 mA...? I am willing to loose a lil brightness, someone told me 1K resistor in series, someone told me a few diodes in series.... I am confused....





RE: reduce led current draw
Probably the best thing to do is to use a series resistor. A 1K Ohm will limit the LED current to less than 10 ma(or even less if the LED really is 12V rated). If you find the LED is too dim then, drop the resistance to 680 or 430 Ohms. If still too bright, increase the resistor to 1200 to 2000 Ohms. The higher the resistance, the less the current, and the less draw from the battery when your motorcycle is not in use.
RE: reduce led current draw
thanx a lot !
these are the specs of the LED
Catalog #: 276-084
Typical MCD is 50. Typical wavelength is 635nm. Lens size is 6mm. Red lens color. Viewing angle is 45°. 15mA (max). Typical Voltage is 12, with a maximum voltage of 12V. Comes as package of 1. Mfg hole diameter is 3/16".
RE: reduce led current draw
that is the link where the LED specs are listed in more detail
RE: reduce led current draw
Your 12V, 15mA pack must be dropping 12 - 2.5 = 9.5V across the internal resistor, giving an internal resistance of 9.5 / 0.015 = 633ish ohms.
To get this down to 5 mA, you need a total resistance of 9.5 / 0.005 = 1900 ohms.
I'd suggest you try an additional series resistor of
1900 - 633 = 1.2k ish ohms.
A.
RE: reduce led current draw
RE: reduce led current draw
It's incredible though, since I made this mod (about 1 week)my motorcycle starts w/o a problem and all this difference just for dropping the current of an LED from 15 mA to 5 mA....????? on a motorvehicle battery...????