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Pot Controlled Variable LED Intensity Circuit - The circuit below uses power from four rechargeable AA NiMH
cells to drive 3 white LEDs. A potentiometer varies the duty cycle of a pulse width modulator circuit to vary the intensity of the LEDs from 0% to 100%. The beauty of the circuit is that when the. . . Circuit by Dave Johnson P.E.-September, 2009 POV Persistence of Vision 2 x 32 LED display - POV stands for Persistence Of Vision. It’s a term that's been applied to devices that rely on the eye's tendency to continue to "see" an image for a short time after it has disappered. This is also what causes the apparent blurring of objects that are in motion (like an airplane propeller) __ Designed by Ian Paterson
Power 220V Flashing LED - AC mains operated single LED flasher circuit, built using the popular CMOS
timer chip TLC555 is shown below. The whole circuit is powered directly by the grid supply of 230VAC through a capacitive potential divider and associated components. This minuscule Power LED Flashing circuit can be easily fit inside a very small __ Designed by T.K. Hareendran
Power an LED Driver using Off-The-Shelf Components - 01/20/11 EDN-Design Ideas Drive LEDs with a 555 timer and two transistors. [Design Ideas by TA Babu, Chennai, India Design by TA Babu, Chennai, India
Power OK LED for PC - Simple, low cost three transistor circuit lights LED only if all four PC power supply voltages +/-5V, +/-12V) are present. __ Designed by Jim Haggerman, Hagerman Technology LLC
Power Supply-24 Volts AC to 24 Volts DC - The idea for the circuit below came from a company needing to power several 24v DC LED assemblies from an existing 24vac supply. They did not need a rock solid and regulated 24 volts but a voltage which hovered around that voltage. Running the AC through. . . Circuit by David A. Johnson P.E.-February, 2011
Power-supply IC drives multiple LEDs - 09/02/04 EDN-Design Ideas Bright LEDs are becoming prominent sources of light. They often have better efficiency and reliability than do conventional light sources. Although LEDs can operate from an energy source as simple as a battery and a resistor, drivin Design by John Lo Giudice and Vee Shing Wong, STMicroelectronics, Schaumburg, I - L
Processor's PWM output controls LCD/LED driver - 27-May-04 EDN-Design Ideas The PWM (pulse-width-modulation] output available from many microprocessors is based on an internal 8- or 16-bit counter and features a programmable duty cycle. It is suitable for adjusting the output of an LCD driver (Figure 1) , a negative-voltage LCD driver (Figure 2], or a current-controlled LED driver (Figure 3] Design by Joe Neubauer, Maxim Integrated Products, Sunnyvale, CA
Programmable LED - Alex Inspired by various LED Throwies, blinking LEDs and similar instructables I wanted to do my version of an LED controlled by a microcontroller. The idea is to make the LED blinking sequence reprogrammable. This reprogramming can be done with __ Designed by Radio LocMan
Programmable LED Flashers - LED goes to steady state after a preset number of flashes; Two simple, wide supply range operating circuits __ Contact: Flavio Dellepiane, fladello @ tin.it
Programmable LED Indicator - This circuit uses CD4017 to program a bicolour LED in ten different modes with combinations of red and green. __ Electronics Projects for You
Propeller Message Display with Temperature Indicator - Here we describe a microcontroller-based propeller display that displays any message sent to it via hyper-terminal of a personal computer. Moreover, a temperature sensing IC (TMP125) is mounted onto the propeller...__ Electronics Projects for You
Propellor clock PIC16F84 - A motor spins the "propeller", and a small microprocessor keeps track of time and changes the pattern on seven LEDs with exact timing to simulate a 7 by 30 array of LEDs. It is an illusion, but it works nicely. __ Designed by Bob Blick
Protect Power-LED Strings From Overcurrent - 06/23/11 EDN-Design Ideas Add diodes and a transistor to a current mirror to prevent LED damage. A common method for driving multiple power LEDs is through two parallel strings. This inexpensive and less critical driver circuit can provide a lower voltage. However, the driver circuit must deliver twice the current of other methods and needs a circuit that halves the current in the two strings, regardless of the LEDs’ forward voltages. The LEDs’ forward-voltage tolerance is as high as 20%, and the voltages change with LED temperature and aging. Design by Luca Bruno, ITIS Hensemberger Monza, Lissone, Italy
Provide High-Side Current-Sensing for White-LED Drivers - 02/19/04 EDN-Design Ideas 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 Design by Dimitry Goder, Sipex Corp, San Jose, CA
Provides Visual Verification of IR Pulses - 09/08/11 EDN-Design Ideas Use a transimpedance amplifier to drive an LED. You can test an IR (infrared) link with a circuit that converts an IR-generated photocurrent to an amplified current that drives a standard LED (Figure 1) . This approach provIdeas a visual feedback to indicate that the transmitter is working. The circuit can be enclosed in a small plastic or metal box and requires just a 9V transistor battery for operation. Diode D1 is a basic Everlight PD333-3C/H0/L2 or equivalent IR photodiode in a T1¾ package. Design by Michael J Gambuzza, General Electric Measurement and Control Solutions, Billerica, MA
Pulsed LED a High Current - Just to Play with, But it Might have some Practical Applications. __ Designed by G.L. Chemelec
Pulsed LED Test Circuit - This circuit is designed to test visible and infrared LEDs in pulsed mode operations. It can drive the LED with peak currents in excess of 10 amps. A light detector nearby can monitor the response time and intensity of the LED under test. . . Circuit by David A. Johnson P.E.-June, 2000
Pulsed LEDA High Current. - Just to Play withBut it Might have some Practical Applications __ Designed by G.L. Chemelec
Pulses for Infrared LEDs & Visible Diode Lasers - This article demonstrates basic circuits for pulsing infrared LEDs and low power visible semiconductor lasers using components which are inexpensive and fairly readily available. Many interesting and useful applications can be found in the references cited here, as well as several online web pages. This article focuses on the basic circuits. __ Designed by M. Gallant
Pushbutton Controlled Up/Down Ramping Light - There are times when you want a lamp to gradually change from dark to light and from light to dark, with each push of a pushbutton switch. The circuit below performs this control function using a flip/flop and a classic pulse width modulation or PWM. . . Circuit by Dave Johnson P.E.-March, 2009
PV Solar Cell Test Fixture - This is an illustration of a test fixture, which can be used to test individual solar cells for short circuit current. Using a PIN photo diode and a control circuit, the solar cells can be tested under constant light level conditions . . . Hobby Circuit designed by David Johnson P.E.-October, 2006
PWM controller drives LEDs from high-voltage lines - 4-Mar-04 EDN-Design Ideas Powering LEDs from a wide dc range—say, 30 to 380V—without wasting a lot of power in the regulating block, is a difficult task when the LED current needs to be constant. Dedicated LED drivers are available, but they usually implement boost structures and are thus inadequate for high-voltage inputs Design by Christophe Basso, On Semiconductor, Toulouse, France |
