Quickar

Current limiting resistor calculator for Led's This Java Script was Graciously provided by the Cool Folks at Metku Mods - "Because you love your hardware" Check em out at "http://metku.net" A browser capable of running Javascript is required for this calculator. Single Led - Series Led's - Parallel Led's Click here for the Luxeon Star Calculator Single led Supply Voltage   VOLTS Voltage Drop Across LED   VOLTS Desired LED Current   MILLIAMPS Calculated Limiting Resistor   OHMS Nearest higher rated 10% resistor   Calculated Resistor Wattage   WATTS Safe pick is a resistor with power rating of   WATTS Leds in series Supply Voltage   VOLTS Voltage Drop Across LED   VOLTS Desired LED Current   MILLIAMPS How many leds connected   Calculated Limiting Resistor   OHMS Nearest higher rated 10% resistor   Calculated Resistor Wattage   WATTS Safe pick is a resistor with power rating of   WATTS Leds in parallel Supply Voltage   VOLTS Voltage Drop Across LED   VOLTS Desired LED Current   MILLIAMPS How many leds connected   Calculated Limiting Resistor   OHMS Nearest higher rated 10% resistor   Calculated Resistor Wattage   WATTS Safe pick is a resistor with power rating of   WATTS

OHMS LAW

The best way to drive LEDS and DC Motors is with Pulse Width Modulation

PWM offers several benefits over a simple current limiting resistor or a current regulator IC

1. Lower Power Consumption

2. Less Heat

3. More Efficient

The current limiting resistor and the linear regulator both have to continiously pass the difference between power in and power out with the result being heat.

In PWM, since the FET is only conducting part of the time, it doesn't use near as much energy, and doesn't get as hot.

All PWM does is chop up the input power ( volts x amps) into "Pulses" of varying width...the wider the pulse, the greater the power is delivered, this gives you control over the brightness of leds, or the speed of small dc motors.

You must always make sure that you either:

A: limit the power going into the pwm circuit so what comes out is not greater than the specifications of your strings of leds, or fans

or

B. limit the power coming out of the pwm circuit , so what comes out is not greater than the specifications of your strings of leds, or fans