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Last Updated: June 02, 2021 01:44 PM

Circuits Designed by Dave Johnson, P.E.

Safety LightMy 1200 square foot metal shop only has one small entrance door and no skylights.  If the lights are turn off while inside, there is not enough light to safely find the door to exit the building.  On a couple occasions, while I was quietly working at my test bench, my wife would walk into the shop, grab a garden tool and rush back out, turning off the lights and closing the door without thinking . . . Hobby Circuit designed by David A. Johnson P.E.-November, 2004

Service_Request_Flasher  -  A single 3v lithium coin cell battery powers the device.  Four super bright green LEDs are flashed when the assembly was rotated into the “Requested Service” position. A tilt switch senses when the device is in that position.  A simple timer turns off the flasher after 3 minutes, if left in the flashing position.   . . . Dave Johnson, Lubbock TX-DC Magazine - Issue 13 Nov 2010




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

Safe Hot Swapping using the LTC1421 -  DN139 Design Notes __ Linear Technology/Analog Devices

Safely Deep-discharges NiCd battery  -  04/29/99  EDN-Design Ideas –  NOTE :  Scroll to find this circuit.   Also available athttp://m.eet.com/media/1150682/25098-42999di     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.  Design by Jim Hagerman, Science & Technology International, Honolulu, HI

Safety Flasher -  This circuit alternately flashes two high-brightness LEDs as a safety measure during jogging or walking.  The LED’s can be mounted on clothing or a belt.  The circuit draws a precisely controlled 10mA in order to conserve battery life.  Also, the battery vol __ Designed by Andrew R. Morris

Safety flasher warns of high voltage -  02/17/14EDN-Design Ideas A low power circuit warns the user that high voltage is presentWorking on high voltage circuits can be dangerous.  Capacitors can maintain high voltage in a system for a considerable time after power is removed Design by Clive Bolton

Safety Light -  My 1200 square foot metal shop only has one small entrance door and no skylights.  If the lights are turn off while inside, there is not enough light to safely find the door to exit the building.  On a couple occasions, while I was quietly working at my test bench, my wife would walk into the shop, grab a garden tool and rush back out, turning off the lights and closing the door without thinking . . . Hobby Circuit designed by David A. Johnson P.E.-November, 2004

Save String Light Situation -  12/16/04 EDN on Components   As you enter the holiday season with strings of ac-line-powered lights hanging everywhere, do you ever wonder how bulb vendors overcame the frustrating problem of having an entire string go dark when just one of th Design by Bill Schweber

ScanmateAudio Activated Recorder -  ScanMate connects between your scanner and tape recorders (via the recorder's microphone or auxiliary input and its remote start jack). __ Designed by Tony van Roon  VA3AVR

SCC3 12V 20A Solar Charge Controller -  The SCC3 kit is the heart of a 12 Volt solar power system, it regulates the charging of batteries from photovoltaic   (PV) solar panels.  A charge controller is an essential part of any solar power system.  A 12 Volt solar power system can provide power to a wide variety of devices such as lighting systems, Ham and CB radios, car stereos, cell phone chargers, laptop computers, televisions, recording equipment, fans, water pumps and other 12V DC loads.  With the addition of a DC to AC inverter, the DC power can be converted to 120 Volts AC for running many household electronic devices. 
 __ Designed by G. Forrest Cook

SCC3 20 Amp 12V Solar Charge Controller -  The SCC3 is a solar charge controller, its function is to regulate the power flowing from a photovoltaic panel into a rechargeable battery.  It features easy setup with one potentiometer for the float voltage adjustment and an equalize function for periodic overcharging.  Automatic temperature compensation optimizes battery charging over a wide range of temperatures.  The SCC3 is robust, it can handle reverse polarity connection of both the battery and photovoltaic panel.   __ Designed by G. Forrest Cook

Scheme Adds Sequencing & Shutdown Control to Regulator -  10/30/03  EDN-Design Ideas Modern microprocessor- or FP-GA-based circuits require separate and independent power-supply voltages for the core and the I/O circuits.  Some devices require stringent control of the turn-on characteristics and sequencing of these  Design by Said Jackson, Equator Technologies Inc, Campbell, CA

Scheme implements multiple output ports -  02/16/98 EDN-Design Ideas In µP/µC systems, you sometimes need to use many output ports and update all the ports simultaneously.  For instance, in systems that use multiplexing techniques, the output ports require refreshing for every scanning period.  One example is a system of multiple dot-matrix LEDsFile has many circuits, scroll to find this one Design by W Kurdthongmee, Nakorn Si Thammarat, Thailand

Scheme Saves String Light Situation -  12/16/04 EDN on Components   As you enter the holiday season with strings of ac-line-powered lights hanging everywhere, do you ever wonder how bulb vendors overcame the frustrating problem of having an entire string go dark when just one of th Design by Bill Schweber

SCR Crowbar -  The LTC1696 is a standalone power supply overvoltage monitor and protection device designed to protect a power supply load in the event of an overvoltage fault.  It monitors two adjustable output voltages.  If an overvoltage condition is detected, the output drives either an external SCR crowbar or turns off external back-to-back__ Linear Technology/Analog Devices App Note, Jul 8th 2011

SCR Flipflop for Alternating Flashing Light Bulbs -  Schematic only __ Designed by G.L. Chemelec

Secondary Side Dual Output Controller Tightly Regulates Two Isolated Outputs -  DN1000 Design Notes  __ Linear Technology/Analog Devices

Secondary-Side Controller Offers Efficiency, Simple Circuit Design -  03/28/96 EDN-Design Ideas Secondary-side, or auxiliary, controllers usually use magnetic amplifiers, because they are more efficient than switching or linear regulators.  Despite their advantages, however, magnetic amplifiers require expensive magnetic cores, design expertise, and extra component-sizing design margins to withstand maximum input voltage during short-circuit and other conditions.  To avoid these drawbacks, the Linfinity Microelectronics LX1570 and LX1571 controllers’ architecture replaces the magnetic-amplifier core with a MOSFET.    Design by Linfinity Microelectronics Inc, Garden Grove, CA

Seismic Sensor -  My original "Deer Repellent/ Seismic Sensor" recommended using a speaker with a weight glued to the cone as a vibration sensor (see bottom of page) but it recently occurred to me that the speaker could supply the mass itself.  By gluing  __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Self Powered Solar Box Furnace -  This project involves the construction of a self contained solar box furnace (Photo 1).  I assembled the prototype with materials that I had laying around my workshop.  It is suitable for heating up a small room or a detached shed.  I use the furnace to warm up my garage, it takes the chill out of a fairly large space when the weather is cold, but sunny.  It is possible to scale this project up to any size, a larger version, or a set of them, could be used to add a lot of supplemental heat a house __ Designed by G. Forrest Cook

Self-timed logic technique cuts noise & power -  06/10/99  EDN-Design Ideas Tired of struggling with the problems of global clock timing and distribution in ASIC design? A solution to at least part of that problem may lie in a change of strategy to self-timed design.   Design by Graham Prophet

Self-Tune Filter -  "QRP" receivers and transmitters, for HF CW are often based upon VFO tuning which can be a problem, especially when using the higher frequency bands.  I have found that frequency drift is quite annoying at the best of times, but back in 1972 I found this little circuit.  It is a narrow band-pass filter, based upon the LM201 OP-Amp.  The circuit should work using other OP-Amps, but I have not tested this; I only used the LM201. __ Designed by Harry Lythall-SM0VPO

Sensitive Remote Control Tester -  Here is a handy gadget for testing of infrared (IR) based remote control transmitters used for TVs and VCRs etc.  The IR signals from a remote control transmitter are sensed by the...__ Electronics Projects for You

Sequencer controls power supplies' turn-on & turn-off order -  18-Jan-07 EDN-Design Ideas Two low-cost ICs and a few passive components prevent disorderly shutdown Design by Eric Schlaepfer, Maxim Integrated Products Inc, Sunnyvale, CA

Sequencing Neons Ne 51/Ne 2 -  This circuit is similar to the LED clock using 12 neon indicator lamps instead of LEDs.  It operates from 2 high capacity ni-cad cells   (2.5 volts) which keep it going for a couple weeks.  High voltage   (70 volts) for the neon lamps is obtained from a small switching power supply using a 74HC14 Schmitt trigger squarewave oscillator, high voltage switching transistor __ Designed by Bill Bowden

Sequential Bar Graph Turn Light Indicator for Car -  The article illustrates a simple yet innovative, fancy car turn signal light circuit which produces a rising bar graph sequence effect when switched ON. __ Designed by Swagatam Majumdar

Sequential Brake/Turn Lights -  Bar-mode LED-cluster sequencer.  Can drive up to 16 clusters.   __ Contact: Flavio Dellepiane, fladello @ tin.it

Sequential Device Control using TV Remote Control -  This circuit lets you switch on and switch off up to nine devices sequentially from your TV remote control.  The circuit consists of an IR sensor module TSOP1738, which is equivalent to...__ Electronics Projects for You

Sequential Flasher -  Scroll to find this one.  Here is an unusual flasher circuit for 120VAC loads.  The circuit is similar to the two-transistor flasher seen in several circuits in techlib.  com except that an SCR is used __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Sequential LED Flasher -  for 10 LEDs.   __ Designed by Tony van Roon  VA3AVR

Sequential state machine aids in automatic control -  2-Sep-04 EDN-Design Ideas Creating a sequential state machine is a common approach for automatic-control design.  The meth-od finds wide use for controlling sequential processes in industry, robotics, and measuring.  The concept of a state machine is simple  A number of states describe a process under control; each state produces some output signals and advances to the next state according to received input signal Design by Abel Raynus, Armatron International, Malden, MA

Serial Infrared Remote Controller -  This is a simple, cheap device that can be connected to any serial port to control most components that have infrared remote controls.  I designed and built it   (on a solderless breadboard) in 1991.  In 1992 I wrote a lengthy description of it for an electronics class.  In 1994 I finally designed a PC board for it, using a free, X-based PC board design program called pcb, and in 1995 I etched several of the boards and made the final product __ Designed by John DuBois

Serial LCD Controller -  Serial LCD/VFD Controller is a HD44870 based LCD/VFD controller via RS-232.  The control command is compatible with Matrix-Orbital's LCD module.  So, you can use any MO friendly software to control this baby such as LCDC. __ Designed by Dick Cappels

Serial LCD controller using a PIC16F628 -  Schematic only, no circuit description included

Serial port drives low-cost, three-wire DACs -  EDN  Design Ideas03/03/1997    The circuit in Figure 1 allows you to control low-cost, three-wire D/A converters through a PC's serial port.  A 74HC14 extracts the three signals (data, clock, and load) from the signal on one wire.  The method relies on the data-pulse width: a short pulse is a logic 1; a long pulse is a logic 0.  The serial-port settings are COM1/9600 baud/no parity/8 data bits.  A logic 1 transmits as 255, which leads to a short pulse (start bit only); a logic 0 transmits as 0, which results in a pulse that's nine times longer.  Figure 2 is the timing diagram for the process. Design by Bernard Willaert, Barco Display Systems, Kortrijk, Belgium

Serial Servo Motor Controller -  Several people contacted me about our other project for controlling hobby servo motors with the PC serial port.  Servo Commander was designed after quite a few people asked for a version of the serial servo controller that would let the user select a different serial port on the PC, and had the ability to control 8 servos.  Several people contacted me about our other project for controlling hobby servo motors with the PC serial port.  Servo Commander was designed after quite a few people asked for a version of the serial servo controller that would let the user select a different serial port on the PC, and had the ability to control 8 servos.   __ Designed by Reynolds Electronics

Serial-driven IR remote Controller -  This paper describes a serial infrared transmitter (SIT)   capable of  generating  the infrared codes used by most current equipment that incorporates an infrared remote control.    It is operated by a computer    through  an  asynchronous  communications port.    Driver software __ Designed by John H. DuBois III

Serial-Interface infrared remote control -  This is a simple, cheap device that can be connected to any serial port to control most components that have infrared remote controls.  I designed and built it (on a solderless breadboard) in 1991.  In 1992 I wrote a lengthy description of it for an electronics class.  In 1994 I finally designed a PC board for it, using a free, X-based PC board design program called pcb, and in 1995 I etched several of the boards and made the final product __ Designed by John DuBois

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