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Last Updated: December 01, 2017 03:41 AM

Circuits Designed by Dave Johnson, P.E.

Circuit Protects from Battery Polarity ReversalThis simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was. . . Circuit by David A. Johnson P.E.-March, 2002



Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Circuit forms DC-motor switch with brake -  10-Jan-02 EDN-Design Ideas Controlling a small dc motor without speed control sounds like a trivial task; a switch or a relay should suffice.  However, several problems accompany this approach.  For one, the switch, because of the inductive load and the low starting resistance of the motor, tends to wear out prematurely(with all the related sparks and EMI problems] __ Circuit Design by JB Guiot, DCS AG, Allschwil, Switzerland

Circuit forms fast, portable light pulser -  16-Oct-03 EDN-Design Ideas The absence of a fast one-shot multivibrator in the entire TTL family, as well as the low-voltage swing and unwieldy supply requirements of ECL, drove us to exploit the fast transition times and low propagation delays of F-series gates.  The application called for the implementation of a compact, portable, fast light pulser for field testing fast photomultipliers in gamma-ray astronomy work __ Circuit Design by SK Kaul and IK Kaul, Bhabha Atomic Research Centre, Trombay, Mumbai, India

Circuit generates fan-speed control -  03/21/02 EDN-Design Ideas Fan noise is becoming a significant issue as electronic equipment increasingly enters the office and the home.  Noise is proportional to fan speed, and the airflow¡ªhence, fan speed¡ªnecessary for cooling is less at low ambient temperatures.  Because ambient temperature is lower than the upper design point most of the time, a fan can run slower, making it easier on the ears __ Circuit Design by Jim Christensen, Maxim Integrated Products, Sunnyvale, CA

Circuit improves on temperature measurement -  05/02/02 EDN-Design Ideas When current pulses with a stable IHIGH/ILOW ratio modulate a semiconductor junction, the ensuing voltage difference (for example, ΔVBE for a bipolar transistor] is a linear function of the absolute (Kelvin] temperature, T.  You can use this truism to make accurate temperature measurements.  Technical literature has thoroughly covered the relationship (references 1 to 4] and has numerous __ Circuit Design by Alexander Bell, Infosoft International Inc, Rego Park, NY

Circuit lets AGC Amp hold its gain -  EDN-Design Ideas 01/19/2015    AGC amps respond to signal level.  This Design Idea allows gain to be held despite a changing level.   AGC (automatic gain control) amplifiers are frequently used devices.  Their gain is a function of the level of their input signal.  The main function of AGC amplifiers is compression of a signal, but sometimes the gain needs to be temporarily frozen.  This Design Idea provIdeas just this function. __ Circuit Design by Vladimir Rentyuk

Circuit Level-Shifts AC Signals -  10-Jul-03 EDN-Design Ideas AC signals can emanate from many sources, and many of these sources are incompatible with the most popular interface voltages, such as TTL.  A temptation always exists to capacitively couple the ac signals because capacitive couplin __ Circuit Design by Ron Mancini, Texas Instruments, Bushnell, FL

Circuit manages power-up sequencing -  31-Oct-02 EDN-Design Ideas Power sequencing poses a unique problem in power management.  Because improper sequencing may cause damage to many types of processors, power-up sequencing of these devices is critical.  Devices that may require power-up sequencing control include FPGAs, ASICs, and DSP chips.  These devices can require tracking I/O and core voltages __ Circuit Design by Martin Galinski, Micrel Semiconductor, San Jose, CA

Circuit Measures Capacitance or Inductance -  10/21/10 EDN-Design Ideas Use instruments you already have and a few equations when you don’t have a capacitance meter.   __ Circuit Design by Jim McLucas, Broomfield, CO

Circuit Precludes Common-Mode Conduction -  4-Feb-10 EDN-Design Ideas A crossover-control circuit prevents two ortransistors from powering on at once __ Circuit Design by Ken Herrick, Oakland, CA

Circuit Protects from Battery Polarity Reversal -  This simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was. . . Circuit by David A. Johnson P.E.-March, 2002

Circuit protects system from overheating -  11/08/01 EDN-Design Ideas The two-chip circuit in Figure 1 provIdeas fan control and overtemperature warning and shutdown signals to protect systems from excessive heat.  The circuit monitors the temperature of the pc board and the die temperature of a CPU, an FPGA, or another IC with an on-chip temperature-sensing transistor __ Circuit Design by Kerry Lacanette, Maxim Integrated Products, Sunnyvale, CA

Circuit provides 4-to 20-mA loop for microcontrollers -  05/27/04  EDN-Design Ideas The 4- to 20-mA current loop is ubiquitous in the world of controls in manufacturing plants.  Discrete logic, microprocessors, and microcontrollers easily cover the digital portions of control schemes, such as limit switches, pushbuttons, and signal lights.  Interfacing a 4- to 20-mA output to a rudimentary microcontroller can be problematic __ Circuit Design by Robert Most, Dow Corning Corp, Auburn, MI

Circuit Provides 70 DB Of AGC -  EDN-Design Ideas -- 02/02/12   A comparator autoranges to ensure that the automatic-gain-control section sees a signal between −60 and −25 dBm, keeping the FET in its linear region.   __ Circuit Design by Ben Segal, Telecommunications Technology, Sunnyvale, CA

Circuit Provides Bidirectional Variable Speed Motor-Contro -  05/16/02 EDN-Design Ideas During the development of systems that include small motors, a simple, bidirectional motor controller with speed adjustment may be heLPFul.  Figure 1 shows such a controller.  The circuit uses everyday components whose tolerances and ratings are unimportant as long as they sustain the required voltage, current, and power __ Circuit Design by Jean-Bernard Guiot, DCS AG, Allschwil, Switzerland

Circuit provides brownout control of 80C31 -  08/19/99  EDN-Design Ideas In the reset and watchdog-timer circuit in Figure 1, IC1 is a 74HC14 Schmitt-trigger inverter that, with R1 and C1, acts as an astable oscillator.  The circuit provIdeas an active-high reset for an 80C31 µC.  The watchdog trigger(WDT) consists of watchdog-trigger pulses __ Circuit Design by N Kannan, Mediatronix, Pappanamcode, India

Circuit Provides Class D Motor Control -  1-May-03 EDN-Design Ideas Class D audio amplifiers provide a dual benefit for battery-powered portable devices.  They enhance battery life, and they produce much less power dissipation than do their linear cousins.  Those features make Class D amplifiers ideal candidates for controlling speed and direction in small electric motors __ Circuit Design by John Guy, Maxim Integrated Products, Sunnyvale, CA

Circuit provides efficient fan-speed control -  4-Mar-04 EDN-Design Ideas As Moore's Law plunges us into the realm of multigigahertz processors and PCs with gigabytes of RAM, engineers face the task of removing the heat that these state-of-the-art components produce.  Cooling such systems poses a dilemma.  If you optimize the fan size and speed for nominal operating conditions, the system is susceptible to failure when conditions deteriorate __ Circuit Design by John Guy, Maxim Integrated Products, Sunnyvale, CA

Circuit provides 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 zener diode, D1 that forms the heart of a constant-voltage source for the laser diode __ Circuit Design by Michael Fisch, Agere Systems, Longmont, CO

Circuit Provides More Accurate Multiplication -  12/15/11 EDN-Design Ideas Convert into and out of the sampled-data domain to get an accurate multiplication.  Common analog multiplying devices employ methods using transistor parameters.  Precise versions of these devices use the logarithm method of multiplication.  This method involves the addition of logarithms and an exponential conversion (Reference 1).  Using these methods, you can achieve a minimal error of ±0.1%.  This Design Idea reduces the error, employs readily available standard components, and maintains the correct voltage scale.   __ Circuit Design by Yakov Velikson, Lexington, MA

Circuit Provides Motor Feed Control -  07/25/02 EDN-Design Ideas Linear power driver works from single supplyBecause we needed a small grinding machine, we modified an old milling machine that lacked a control system.  The table of the grinding machine needed only to move back and forth with __ Circuit Design by Jean-Bernard Guiot

Circuit remotely adjusts PSU voltage -  EDN-Design Ideas 01/28/2016    This DI circuit allows for remote regulator/PSU programmability or trimming. __ Circuit Design by Chee Hua How

Circuit safely Deep-discharges NiCd battery  -  04/29/99  EDN-Design Ideas –  NOTE :  Scroll to find this circuit.   Nickel-cadmium (NiCd) batteries can possess an undesirable memory effect due to partial discharges. The remedy is a complete discharge before charging again. Figure 1a shows a simple circuit that performs this feat.  __ Circuit Design by Jim Hagerman, Science & Technology International, Honolulu, HI

Circuit Smoothly Drives Stepper Motors -  05/28/09  EDN-Design Ideas Adding an analog switch make the motor bidirectionalThe circuit in This design idea     drives low-power, unipolar stepper motors using only a shift register, a few resistors, and low-power transistors.  Adding an inexpensive 4053 an __ Circuit Design by Uwe Schüler, Institute of Physiology, Tübingen, Germany

Circuits provide 4- to 20-mA PWM control -  09/01/98 EDN-Design Ideas The circuits in Figure 1  and Figure 3 are useful when you use 4- to 20-mA current-loop signals to control a PWM signal.  In both circuits, the minimum pulse width(corresponding to a 4-mA loop current) and the maximum pulse width(corresponding to a 20-mA loop current) are independentlyFile has many circuits, scroll down __ Circuit Design by Tom Gay, Darmstadt, Germany

Clairvoyance Marries Remote Sensing -  Linear Technology AN126 __ Designed by Jim WilliamsOct 1st, 2010

Clap Activated Remote -  In infra-red or wireless remote control has the disadvantage that the small, handy, remote transmitter is often misplaced.  The sound operated switch has the advantage that the transmitter is always with you.  This project offers a way to control up to four latching switches with two claps of your hand.  These switches may be used to control lights or fans ? or anything else that does not produce too loud a sound.

Clap On / Off Switch -  Clap On / Off Switch Diagram This is the circuit diagram of Clap On / Off Switch.  The circuit allows you to operate your lighting or any circuit device which use 24V / 3A maximum supply, simply by clapping your hands. It has a relay output that can be used to turn external devices on/off.  This

Clap operated remove control for fans -  Here is the circuit of clap-operated remote control fans is used to control not only switching properties but also control speed of fan.  The main advantage of clap operated remote control for fan is, it can control up to ten-step speeds of fan where normally a fan has three to five step speeds

Clap Relay -  Clap sensitive on-off Relay.3V Battery operated, small portable unit,  __ Contact: Flavio Dellepiane, fladello @ tin.it

Clap Remote -  An infra-red or wireless remote control has the disadvantage that the small, handy, remote (transmitter) is often misplaced.  The sound operated switch has the advantage that the transmitter is always with...__ Electronics Projects for You

Clap Sound Light Switch -  This box is a 40Khz ultra-sound detector, with a latch and an output relay, when you clap your hands, the relay turn the light on, when you clap again the light goes off.  The 3 holes was LEDs, showing ON or OFF state, and ultra-sound level, The 3 LED is floting arround inside the box, I did not glue them enough :-)   A potentiometer is used to adjust the sensitivity. __ Designed by Thomas Scherrer OZ2CPU

Clap Switch -  Here’s a clap switch free from false triggering.  To turn on/off any appliance, you just have to clap twice.  The circuit changes its output state only when you clap twice within...__ Electronics Projects for You

Clap Switch -  A clap switch circuit is a classic beginner’s project.  Equipment can be switched on and off by just clapping your hands.  Add a tiny microcontroller and you can easily build-in some more useful features.  The microcontroller in this circuit makes it a simple job to add some useful features that are not seen on other clap switch __ Designed by Popescu Marian

Clap Switch Circuit -  This is a simple clap switch circuit with high sensitivity.  The only unusual component is the single coil latching relay.  While there are numerous means of generating the latching function, the latching relay greatly simplifies the circuit and provides a relay contact interface for driving a 115 or 230VAC load such as a light bulb.

Clap Switch Diagram -  Here’s a clap switch free from false triggering.  To turn on/off any appliance, you just have to clap twice.  The circuit changes its output state only when you clap twice within the set time period.  Here, you’ve to clap within 3 seconds.  The clap sound sensed by condenser microphone is amplified by transistor T1.  The

Clap-Based Digital Volume Control -  This clap-based digital volume control offers four levels of volume control.  With each clap, the volume of the audio system increases.  After the fourth clap, the level of volume returns to...__ Electronics Projects for You

Clap-Operated Electronic Switch -  Here’s a simple clap-operated electronic switch.  Using this switch, you can turn on any appliance by clapping five times and turn it off by a single clap.  The switch activates the...__ Electronics Projects for You

Class D Motor Control -  05/01/03  EDN-Design Ideas Class D audio amplifiers provide a dual benefit for battery-powered portable devices.  They enhance battery life, and they produce much less power dissipation than do their linear cousins.  Those features make Class D amplifiers ideal __ Circuit Design by John Guy, Maxim Integrated Products, Sunnyvale, CA

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Control Circuits:   #'s - A       B - C       D - G        H - L       M - P        Q - S        T - U        V - Z


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