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Keypad Controlled Switch No.2 - Universal Keypad-Controlled Switches: This is a simplified version of the 4-Digit Keypad Controlled Switch. I have modified the design to reduce the complexity of the circuitand the number of components required. As a resultthe code is somewhat less secure. However, there should be lots of situations where it will still be adequate. __ Designed by Ron J.
Keypad sequence activates relay - 10/12/00 EDN-Design Ideas Today, it seems that µPs assume even the easiest tasks, such as activating a relay(for an alarm or access control, for example]via a keyboard command. However, a simpler and less expensive solution is available(Figure 1). Moreover, the method does not entail programming and the concomitant, almost inevitable, Design by JB Guiot, DCS AG, Allschwil, Switzerland
Knight Rider Lights-LED Chaser - I don't know why, but people like blinking lights. You see LED chasers everywhere, in TV shows (Knight Rider) , movies, and store windows. This schematic is my version of a simple 10 LED chaser. There is no 555 timer used because __ Designed by Aaron Cake
Knight Rider Look-a-like Lights - 12 Volt Knight Rider, "Look-A-Like", Lighting Systems Revised "JAN.2, 2008" (Errors on Knight-3, Corrected) __ Designed by G.L. Chemelec
Knightrider lights for Model cars - This simple circuit drives 6 LEDs in 'Knightrider scanner mode'. Power consumption depends mainly on the type of LEDs used if you use a 7555 (555 CMOS
version). __ Contact: IQ Technologies
Kodak Max flash unit - Schematic for the Kodak Max flash unit __ Designed by Don Klipstein
Lamp Dimmer Full Wave SCR (120 Volt AC) - The full wave phase control circuit below was found in a RCA power circuits book from 1969. The load is placed in series with the AC line and the four diodes provide a full wave rectified voltage to the anode of a SCR. Two small signal transistors are connected in a switch configuration so that when the voltage on the 2.2uF capacitor reaches about 8 volts, the transistors will switch on and discharge the capacitor through the SCR gate causing it to begin conducting. The time delay from the beginning of each half cycle to the point where the SCR switches on is controlled by the 50K resistor which adjusts the time required for the 2uF capacitor to charge to 8 volts. As the resistance is reduced, the time is reduced and the SCR will conduct earlier during each half cycle which applies a greater average voltage across the load. With the resistance set to minimum the SCR will trigger when the voltage rises to about 40 volts or 15 degrees into the cycle. __ Designed by Bill Bowden
Lamp Dimmer-120 VA - C - The full wave phase control circuit below was found in a RCA power circuits book from 1969. The load is placed in series with the AC line and the four diodes provide a full wave rectified voltage to the anode of a SCR. Two small signal transistors are connected in a switch configuration so that when the voltage on the 2.2uF __ Designed by Bill Bowden
Lamp Flasher - This circuit adopts the rather unusual Bowes/White emitter coupled multivibrator circuit. The oscillation frequency is about 1Hz and is set by C1 value. __ Contact: Flavio Dellepiane, fladello @ tin.it
Lantern Flasher/Dimmer - Basically a high-efficiency dimmer, but can also be used as a flasher. In dimmer mode, the LM358 (dual op-amp) is wired to send pulses at a constant frequency. By adjusting the width of these pulses, brightness of the bulb is controlled. In flasher mode, the same potentiometer is used to control the frequency, from about 1 to 20 flashes per second__ tomzi.geo page
Lantern Flasher/Dimmer - The electronic lantern control circuit (fig.1) adds high-efficiency dimming and flashing to an existing battery-powered lantern or flashlight or to a custom design. For the car it makes a great lamp for changing a flat tire, back seat reading or emergency engine work. The flasher mode is useful for warning other drivers __ Contact: Charles Wenzel of Wenzel Associates, Inc.
Lantern Flasher/Dimmer - The electronic lantern control circuit adds high-efficiency dimming and flashing to an existing battery-powered lantern or flashlight or to a custom design. For the car it makes a great lamp for changing a flat tire, back seat reading or emergency engine work. The flasher mode __ Designed by Tony van Roon VA3AVR
Large capacitor charge Controllers - Here's a basic cap switch that will connect capacitor to ground only when it's charged to within 0.4-0.7V from battery voltage (otherwise, it's charging through a 22 Ohm resistor, which can be a low-power 12V lightbulb, too) __ Contact: klausmobile @ yahoo.Com
Laser transmitter/receiver - This set of two circuits from the basis for a very simple light wave transmitter. A LASER beam is modulated and then aimed at a receiver that demodulates the signal and then presents the information (voice, data, etc). The whole thing is very easy to build and requires no specialized parts execpt for the LASER itself. LASERs are available from MWK Industries. __ Designed by Aaron Cake
Laser-diode control - 09/19/02 EDN-Design Ideas Laser diodes are sensitive to ESD, rapid turn-on currents, and overvoltage conditions. To address those problems, the simple laser-diode controller in Figure 1 has several functions. The first part of the circuit comprises an 8.2V Design by Michael Fisch, Agere Systems, Longmont, CO
Latching Continuity Tester - A continuity tester is a must on every service bench for testing cables, pc-boards, switches, motors, plugs, jacks, relays, and many other kinds of components. But there are times when a simple continuity test (or your multi-meter) doesn't tell the whole story. For example, vibration-induced problems in automobile wiring can be extremely difficult to detect because a short or open is not maintained long enough for a non-latching tester to respond __ Designed by Tony van Roon VA3AVR
Lazy ISP Adaptor for Socketed AVR ISP Controllers - The Lazy Adapter is composed of a 20 pin DIP socket, a 20 pin DIP header, and 6 pin ISP header, and a small phenolic circuit board to hold them all together. The green fiberglass PCB is a Dontronics DT104 SIMSTIC (This plug is in return for a favor.) __ Designed by Dick Cappels
LDR light/dark activated relay switch - We wanted to do a light/dark switch as a kit. But we found there were several types of basic circuit. This is one type of circuit. Two other types may be found in Kits 79B and 79C. __ Designed by R. M. Marston
LED Bargraph Optical Tachometer - For the electric R/C enthusiast, a tachometer can be a very useful piece of equipment. When I first built this tach back in 1995, it was essential, as there were very few off-the-shelf electric R/C power systems that just worked. __ Designed by Stefan Vorketter
LED Blinking for Embedded Systems - Smart hardware design can simplify the embedded software and make it more reliable. Designers use blinking LED signals to indicate different status and for inbuilt testability. Making an LED array blink...__ Electronics Projects for You
LED brightness control - It's easy to alter the brightness of an LED simply by varying the current through it. __ Designed by Richard Torrens
LED Camping Lantern with Dimmer - A while back I received an email from a Discover Circuits visitor who wanted to build his own LED camping lantern. He wanted to use a single bright LED powered by 3 large alkaline D cells. He also wanted to be able to dim the light intensity down to a low night light level, to extend the battery life. The circuit below performs this task . . . Hobby Circuit designed by Dave Johnson P.E.-December, 2013
LED Chaser - I don't know why, but people like blinking lights. You see LED chasers everywhere, in TV shows (Knight Rider) , movies, and store windows. This schematic is my version of a simple 10 LED chaser. There is no 555 timer used because __ Designed by Aaron Cake
LED Chaser - This is the circuit of a simple LED chaser. The LEDs lights one by one for a period of 1second and the cycle repeats giving the running light appearance. The circuit uses two ICs (one is 555) to drive the LEDs. IC1 (NE555) is the popular timer IC wired in the Astable Multivibrator mode. Resistors R1, VR1 and capacitor C1 act __ Designed by D Mohankumar
LED Chaser - A sequential light chaser using the PIC 12F629. __ Designed by Jose Pino
LED Chaser II - LED Chaser Version 2, Improved. Use it as "LED chaser" or "Third Brake Light". __ Designed by Jose Pino
LED Christmas Tree with 64 LEDs - The Holidays are once again upon us and we wanted to give our readers the edge in decorating this year. Continuing our all-digital-hardware theme to coincide with our Kickstarter for a Digital Electronics Course at PyroEDU, we have created an LED Christmas tree controlled entirely by digital logic __ Designed by PyroElectro
LED Dimmer - Find out how to put together a simple but efficient PWM dimmer circuit for LEDs. __ Designed by REUK-Renewable Energy UK website
LED dimmer uses only two lines - 03/21/02 EDN-Design Ideas The circuit in Figure 1provIdeas 32 steps of brightness control-from 0 to 100%-for a backlight or instrument panel, using just two general-purpose-microprocessor signals. In addition, the circuit requires little board space, because it uses only three SOT-23s and one µMax package Design by Jerry Wasinger, WallyWare Inc, Norcross, GA
LED driver provides software-controlled intensity - 09/30/04 EDN-Design Ideas Recent advances in operating efficiency have expanded the use of LEDs from one of mere indicators to becoming driving forces in electronic lighting. Increased reliability and ruggedness (versus other lighting technologies] gives the Design by Neda Shahi and Bjorn Starmark, Maxim Integrated Products, Sunnyvale, CA
LED drivers minimize power dissipation - 02/01/07 EDN-Design Ideas Reference source and pullup resistor improve efficiency Design by Fons Janssen, Maxim Integrated Products Inc, Bilthoven, Netherlands
LED Driver-Wireless - The circuit solves this problem by sending power to the LED through the plastic, using a magnetic coupling technique. The circuit below can route power through plastic enclosures as thick as ¼ inch. The circuit will not work through metal boxes . . . Hobby Circuit designed by David A. Johnson P.E.-November, 2008
LED Drives Flash-and-Beep - 06/05/97 EDN-Design Ideas Sometimes, you need an alarm that is both audible and visible in an application that's stingy with space, power, and budget. The circuit in Figure 1a is compact, efficient, and inexpensive. The F336HD flashing LED (part no.276-036 at Radio Shack) is a useful device. It operates directly from 5V and produces a consistent pulse of light at approximately 1 Hz without a time-constant capacitor. Design by Dennis Eichenberg, Parma Heights, OH
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