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White LED
(White Light Emitting Diodes) Circuits
White LEDs: #-B
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LED Circuits
Last Updated on:
Monday, October 03, 2011 06:08 PM |
| Circuits Designed by Dave
Johnson, P.E. : |
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Ramping LED Driver
The circuit below was designed to drive a LED with an intensity ramping mode.
Two 555 timers generate two different triangle waveforms. The upper device
generates a 10KHz signal while the lower unit produces a 1Hz signal. The two
signals are fed to a voltage comparator. The result is a pulse width
modulation (PWM) signal, which with the aid of the FET, drives the LED in such a way
that its average light output slowly ramps from about zero light to maximum and then
slowly dims back down. The circuit should operate over a supply voltage ranging
from 3v to 12v. You can easily vary the ramping time by changing the value of the 1M
resistor. For an interesting effect, you can place a 1N4148 diode in parallel
with the 1M resistor, with the cathode (banded end) side connected to pin 3.
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Ramping Lamp Driver 2
This circuit drives any 12v lamp, incandescent or LED type, in a ramping fashion.
Each press of the button toggles the lamp from a fully off mode to a fully on mode.
But, instead of an instantaneous lamp intensity change, the power is slowly ramped
up and down. With the components shown, the ramping action takes two seconds
to complete. By changing the capacitor C3, you can increase or decrease the
ramping time. The circuit will also operate with supply voltages ranging from
15v to 3v.
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Links to electronic circuits,
electronic schematics, designs for engineers, hobbyists, students & inventors:
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Ramping LED Driver - The circuit below was designed to drive a
LED with an intensity ramping mode. Two 555 timers generate two
different triangle waveforms. The upper device generates a 10KHz
signal while the lower unit produces a 1Hz signal. The two signals
are fed to a voltage comparator...... [Designed by David A. Johnson] |
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Regulated 20 mA Dual White LED Lamp - Simple, reliable regulated
night light [G. Forrest Cook] |
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Regulated 24 Watt Broad Spectrum LED Lamp - ultra-bright [G.
Forrest Cook] |
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Regulated Dual 3 Watt White LED Lamp - bright enough to work
under [G. Forrest Cook] |
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Scheme provides high-side current-sensing for white-LED drivers -
19-Feb-04 Issue of EDN White LEDs find wide use in backlighting
color-LCD screens in most portable devices, such as cellular phones, PDAs,
and MP3 players. Multiple LEDs often connect in series to ensure that the
same current flows through every LED. To forward-bias these LEDs, a
voltage of 10 to 16V comes from an inductor-based boost regulator, such as
an SP6690..... [Design Idea by Dimitry Goder, Sipex Corp, San Jose, CA] |
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Self-oscillating H bridge lights white LED from one cell - 26-Nov-09 Issue
of EDN Circuit operates on batteries as low as 0.6V..... [Design Idea by Luca
Bruno, ITIS Hensemberger Monza, Lissone, Italy] |
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Series Connected Voltage Boost Circuit for a Battery Operated LED Lantern -
A circuit that goes in series with a white LED and a 1.5 volt cell to make > 3 Volts
to drive a white LED.....(schematic / circuit added 6/07) |
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Series White LED Driver - National Semiconductor Application Note LM3590
November 2003.....[App Note] |
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Seven Component Regulated LED Lamp - This is a minimal parts lamp made with
four white LEDs. It features regulated light output from 10V to around 20V and works
well as a flashlight. [G. Forrest Cook] |
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Simple Circuit Drives Latching Relays - 02/01/96 EDN-Design Ideas.....Figure
1 shows a low-parts-count circuit that can drive one- or two-coil latching relays.
Latching relays are useful in sensitive analog designs. The 74ACT174 hex flip-flop has
ample capability to drive the Aromat TQ2E series of latching relays. Both windings for
the TQ2E-L2-5V two-coil relay are on the same magnetic element, so the windings'
fields add. You..... [Design Idea by Roy McCammon, 3M Austin, TX] |
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Simple single cell white LED driver uses improvised transformer - 15-Feb-07
Issue of EDN Minimal component-count circuit boosts a single cell's voltage to
light an LED..... [Design Idea by Jim Grant, Scientific Controls, Orlando, FL; Edited
by Brad Thompson and Fran Granville] |
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