High-Speed Pulse Modulator Retains Signal Envelope - 06-Aug-09 EDN Design Ideas: Modulated signals have the ac components they need to pass through transformers. - The circuit in Figure 1 enables you to convert an arbitrary, relatively slowly varying voltage waveform to a new waveform in which the instantaneous values of the original waveform alternate with positive and negative signs. The new waveform retains information about the original waveform, . Design by MariƔn Stofka, Slovak University of Technology, Bratislava, Slovakia
High-Voltage DC Generator - Voltage, by definition, is the electrical pressure that causes current to flow through a conductor. When that pressure is sufficiently high, a high voltage is produced. But how do we define high-voltage? is 100, 1000, or 10, 000 volts considered high voltage? When compared to 10 volts, they all can be considered high voltage __ Designed by Tony van Roon VA3AVR
Honeybee Counter - i designed a circuit similar to this one a long time ago to help a beekeeper count the number of bees going into or out of a hive. The low power circuit uses a slotted opto-sensor to detect the passing bees. The circuit advances an electronic counting. . . Circuit by David A. Johnson P.E.-July, 2000
LED Flashing Badge #1 - i have seen numerous flashing light badges at trade shows and conventions. They are often handed out as gifts to promote some business. The devices often use inefficient circuits, which cause the battery power source to be quickly depleted. . . Circuit by David Johnson P.E.-March, 2002
LED Flashing Badge #2 - This circuit uses a CD4013 dual D Flip/Flop iC. A single lithium battery will provide months of continuous LED flashing. it also has a tiny push-button switch to turn on and off the light flashing. . . Circuit by David A. Johnson P.E.-March, 2002
LM324 Pulse Width Modulator - Schematic only, no circuits description. __ Designed by Tony van Roon VA3AVR
Load Pulser Tests Supply's Transient Response - 04/11/96 EDN Design Ideas: Modern µPs place severe demands on the transient response of the power source. For example, intel's P6 specification stipulates an output-current capability of at least 30A/µsec while maintaining output-voltage regulation within specified limits Design by Chester Simpson, National SemiConductor, Santa Clara, CA
Miniature Pushbutton On/Off Switch - in many battery powered devices, you would like to turn the circuit on and off by pressing a small pushbutton switch. One press turns the device on and second press turns it back off. The flip/flop circuit below uses a minimum number of parts to perform . . . Hobby Circuit designed by David Johnson P.E.-October, 2005
Minimize the Short-Circuit Current Pulse in a Hot-Swap Controller - 27-May-04 EDN Design Ideas: Because of internal circuit-breaker delay and limited MOS-gate pulldown current, many hot-swap controllers do not limit current during the first 10 to 50 µsec following a shorted output. The result can be a brief flow of several hundred amperes. A simple external circuit can counter this problem by minimizing the initial current spike and terminating the short circuit within 200 to 500 nsec Design by Jim Sherwin and Thong Huynh, Maxim Integrated Products, Sunnyvale, CA
Monostable Flip Flops (One Shot) - The two circuits below illustrate using the 555 timer to close a relay for a predetermined amount of time by pressing a momentary N/O push button. The circuit on the left can be used for long time periods where the push button can be pressed and released before the end of the timing period. For shorter periods __ Designed by Bill Bowden
Multiple Pulse Generator - i used this circuit to ring my doorbell rapidly three times when a car pulled into my driveway. R2 and C2 set the output frequency. Use a diode and resistor to change the duty cycle, if desired. R1 and C1 set the cycle time which sets the number of pulse __ Designed by Andrew R. Morris
On/Off Flip/Flop Circuit with Automatic Timeout - This circuit is ideal when a device needs to be turned on and off with a single pushbutton switch, but also needs to turn itself off after some period of time. With the components shown, the output will stay on for only about 20 seconds. . . Circuit by Dave Johnson P.E.-May, 2012
One Hz Pulse Frequency Generator - Here is a 1Hz pulse/frequency generator using the popular timer IC 555 which is wired as an Astable Multivibrator. The output pulses can be indicated visually by the LED. An Astable Multivibrator, often called a free-running Multivibrator, is a rectangular-wave generating circuit. Unlike the Monostable Multivibrator, this __ Designed by D Mohankumar
One Shot (D-Flip/Flop) Circuit - Yes you can use cheap D flip/flop logic circuits as nice one-shot pulse generators. This schematic shows how the popular CD4013 and the CD74HC74 can be used to generate pulses ranging from nanoseconds to seconds. . . Circuit by David A. Johnson P.E.-June, 2000
Oneshot & Latch Pushbutton - This circuit uses a single IC to convert a noisy pushbutton switch signal into a clean pulse or a sustained push on-push off signal. it can operate from 3v to 18v . . . Hobby Circuit designed by David Johnson P.E.-March, 2002
Op Amp as a Set/Reset Flip-Flop - 05/24/12 EDN Design Ideas: Eliminate a flip-flop package by using a spare op amp for an SR latch function. You can make a set/reset flip-flop from two NAND or NOR gates or use readily available set/reset flip-flop iCs, such as the 74HC279 quad-set/reset latch. The drawback of these methods is that they require a large amount of space to form the flip-flop. Even if you need only one flip-flop, you must use a large IC package with this approach. However, you can use a spare rail-to-rail op amp to perform the needed latch function (Figure 1). Design by Aruna Rubasinghe |