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Control Circuits

 
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Last Updated: October 24, 2017 02:54 PM

Circuits Designed by Dave Johnson, P.E.

Ultra Low Current 3v LED Flasher #3This circuit takes advantage of a tiny LMC7215 low current draw voltage comparator from National Semiconductor and a super efficient green LED from King Bright.  The 3v powered circuit forms a classic pulse generator circuit, which drives the LED.  The pulse width is set at about 20ms, the pulse rate is about 0.5Hz and the peak LED current is only 100ua. . . Circuit by David A. Johnson P.E.-February, 2011

Ultra Low Current OscillatorHere is a challenge.  Design an astable oscillator which draws only a few nanoamps of current from a +3v supply.  I gave this some thought and came up with the circuit below.  I used some pretty standard parts except for three surface mounted 1000M resistors I had on hand.  The oscillator frequency measured a low 1Hz frequency and the average current was a very low 3 nanoamps.  If I had some higher resistors values handy, I think I could have gotten the current down below one nanoamp. . . Circuit by Dave Johnson P.E.-March, 2009

Under/Over Voltage Alarm on AC LinePower lines, which deviate much beyond normal voltages can damage expensive electronic equipment.  The circuit below sounds an alarm whenever the line voltage is higher or lower than normal.  I set the alarm limits at about +-15% from standard levels. . . Circuit by David Johnson P.E.-March, 2009

Universal Flasher using a Latching RelayLatching relays are nifty devices.  Most contain two separate coils.  When a voltage is applied to one coil the relay latches in one state and stays in that state until voltage is applied to the unlatch coil.  Since the latching and unlatching pulses only . . . Hobby Circuit designed by David Johnson P.E.-October, 2005

Universal LED FlasherThis low power LED flasher circuit draws about 100ua from any DC power supply ranging from 3 volts to 24 volts.  The 1.0Hz 10ms LED pulsed current is held to a constant 10ma. . . Circuit by David A. Johnson P.E.-July, 2006

Universal-3v-LED-FlasherThe circuit below will flash any LED color with fixed current pulses powered by a 3v battery.  It uses a charge pump approach, which routes a constant current pulse through the LED, regardless of the LED voltage requirement.  Using this approach, white and. . . Circuit by David A. Johnson P.E.-June, 2008

Up/Down Ramping Light Pushbutton ControlThere 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 David A. Johnson P.E.-March, 2009


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

UHF Remote 2-Channel 230VAC Power Switch -  If you're looking for a mains "switch" which can be operated from some distance away, this low-cost, simple project could be just what you want.  With a UHF remote control and two switched "channels", it needs very little power thanks to the use of latching relays.__ SiliconChip

UHF Remote Controlled Mains Switch -  Want to switch mains appliances on and off remotely? This UHF Remote Mains Switch can do it for you.  It's operated using a hand-held UHF transmitter or you can team it with the Water Tank Level Meter Base Station described last month to automatically control mains-operated water pumps.  An in-built timer also enables the unit to turn off automatically after a preset period.__ SiliconChip

UHF Remote Mains Switch Transmitter -  Designed to control the UHF Remote Mains Switch, this hand-held transmitter can operate over a 200m range.  It's based on a PIC micro and a pre-assembled transmitter module, making it easy to build and get going.__ SiliconChip

Ultimate Universal Remote Control -  19-Aug-2009   Couch potatoes should be particularly interested in Bill Bowden's remote control IR receiver, which allows users to control the power of virtually any electrical appliance (including those not equipped for remote) using their standard remote control.  It's based on an IR receiver circuit, which is basically a simple toggle switch that features a 48KHz IR receiver module to convert IR signals to 5V digital data representing the particular command sent. So switch a fan or lights on and off, blend up a pitcher of margaritas, pop popcorn and more, all without leaving your couch a euro " possibly ever. __ Gadget Freak-Case 147

Ultra Low Current 3v LED Flasher #3 -  This circuit takes advantage of a tiny LMC7215 low current draw voltage comparator from National Semiconductor and a super efficient green LED from King Bright.  The 3v powered circuit forms a classic pulse generator circuit, which drives the LED.  The pulse width is set at about 20ms, the pulse rate is about 0.5Hz and the peak LED current is only 100ua. . . Circuit by David A. Johnson P.E.-February, 2011

Ultra Low Current Oscillator -  Here is a challenge.  Design an astable oscillator which draws only a few nanoamps of current from a +3v supply.  I gave this some thought and came up with the circuit below.  I used some pretty standard parts except for three surface mounted 1000M resistors I had on hand.  The oscillator frequency measured a low 1Hz frequency and the average current was a very low 3 nanoamps.  If I had some higher resistors values handy, I think I could have gotten the current down below one nanoamp. . . Circuit by Dave Johnson P.E.-March, 2009

Ultra Low Power LCD Indicator -  This circuit serves as an ultra-low power replacement for multiple LED on-off indicators.  It also has the advantage of being easy to read in full daylight.  With the parts shown, it is possible to display four bits of information.   __ Designed by G. Forrest Cook

Ultra-Bright LED Lamp -  This ultra-bright white LED lamp works on 230V AC with minimal power consumption.  It can be used to illuminate VU meters, SWR meters, etc.  Ultra-bright LEDs available in the market cost...__ Electronics Projects for You

Ultra-Sensitive Solid State Clap Switch -  Here is the circuit of a highly sensitive clap switch that can be operated from a distance of up to 10 metres from the microphone.  Signals picked up by the microphone are amplified by transistors T1, T2, and T3.  Diode D1 detects clap signals and the resulting positive voltage is applied to the base of

Ultrasonic Dog Whistle -  It's well known that many animals are particularly sensitive to high-frequency sounds that humans can't hear.  Many commercial pest repellers based on this principle are available, most of them operating in the range of 30 to 50 kHz.   __ Designed by Tomaz Lazar-Ljubljana, Slovenia

Ultrasonic Remote Control and Intruder Detector -  This transmitter is designed to work with the next circuit as a remote control transmitter/receiver. It is only a single channel and you could once get multi-channel chips for the whole job. However ultrasonics have fallen out of favour commercially so I think most of these chips are now obsolete. __ Designed by Richard Torrens

Under/Over Voltage Alarm on AC Line -  Power lines, which deviate much beyond normal voltages can damage expensive electronic equipment.  The circuit below sounds an alarm whenever the line voltage is higher or lower than normal.  I set the alarm limits at about +-15% from standard levels. . . Circuit by David Johnson P.E.-March, 2009

Underfloor Heating Controller -  This circuit was designed to control the underfloor heating pump independently or via the switch in the living room thermostat.  The design has been made very flexible and can be connected in four different waysmust register on this site __ Designed by Published in Elecktor July/Aug, 2010

Unidirectional RF wireless transmitting & receiving -  Digital in, digital out, with no wires!!! Yes, it can be that easy but there are some things you will find out about going wireless that you may not have counted with wired connection.  This App Note will guide you through a simple RS232 link and illustrate how easy these devices are to use as long as you know how to handle a couple wireless phenomenon and plan your project to take these into account.   __ Contact: info @ wzmicro.com

Uninterruptable Power Supply -  This circuit is a simple form of the commercial UPS, the circuit provides a constant regulated 5 Volt output and an unregulated 12 Volt supply.  In the event of electrical supply line failure the battery takes over, with __ Designed by Andy Collinson

Unipolar Stepper Motor Control -  This circuit controls a small, four-phase, five-wire, unipolar stepper motor, commonly designated the "KP4M4-001.  " This type of motor was used in many 5 1/4" floppy disk drives in older computers.  Now obsolete, such disk drives are often available on the surplus market for a small fraction of the motor's original cost.  The stepper motors are easy to extract from the drives, and are ideal for many applications.  This arrangement was used in the scale model of a RADAR set to control the position of a miniature parabolic antenna.  (Note that some 5 1/4" floppy disk drives used a four-wire "bipolar" motor, which is not compatible with this circuit.)  __ Designed by Arthur Harrison

Unipolar Stepper Motor Controller -  This is a very good integrated circuit.  There is no need for any external glue logic to drive the circuit, there is only 2 pins to drive the motor, one for controlling the direction and the other to trigger the stepping pulses.  It provides a very compact design that drives 5 or 6 or 8 wire stepper motors.  The 5 or 8 wire stepper motors are treated as a variation on the 6 wire motor.  That is, the 5 has the two common wires from the coils center taps joined inside the motor (saves joining them outside the motor), __ Designed by R Ward

Universal Compensator Neutralizes Temperature Coefficient -  05/25/95 EDN-Design Ideas The universal thermal-compensation module in Fig 1  can neutralize the temperature coefficient of both signs within a �0.6%/�C range.  The circuit can compensate the temperature coefficient of offset voltage, gain, sensitivity, or, in general, the linear terms of a device's overall temperature behavior.  The circuit consists of a pair of negative-temperature-coefficient(NTC) thermistors, labeled RT, and of fixed resistors with calculated values that reduce the inherent nonlinearity of the thermistors __ Circuit Design by Alexander Belousov,  Standard Motor Products, Long Island City, NY

Universal Flasher -  LED flasher with the LM3909 IC and runs from1.5-Volt battery.   __ Designed by Tony van Roon  VA3AVR

Universal Flasher using a Latching Relay -  Latching relays are nifty devices.  Most contain two separate coils.  When a voltage is applied to one coil the relay latches in one state and stays in that state until voltage is applied to the unlatch coil.  Since the latching and unlatching pulses only . . . Hobby Circuit designed by David Johnson P.E.-October, 2005

Universal Infrared Controller for a PC -  This simple circuit allows you to record any Infrared remote control signal on your PC, and then play it back.  This is particularly useful if you want to control appliances such as TVs, VCRs, CDs etc.  from your computer.  The device simply connects to the parallel port of your PC.   This circuit was originally published in Electronics Australia, September1998  __ Designed by shaunwilson19 @ yahoo.com

Universal IR Remote Control Tester -  This tester consists of two integrated remote control receivers whose outputs drive an LED to indicate when a suitable infrared signal is received.  To cover all current infrared remote controls, one receiver (the TSOP1736) has maximum sensitivity to carriers at 36 kHz, the other (the TSOP1738) to carriers at 38 kHzmust register on this site __ Designed by Published in Elecktor July/Aug, 2010

Universal LED Flasher -  This low power LED flasher circuit draws about 100ua from any DC power supply ranging from 3 volts to 24 volts.  The 1.0Hz 10ms LED pulsed current is held to a constant 10ma. . . Circuit by David A. Johnson P.E.-July, 2006

Universal RC5/RC6 Transceiver with PIC16F628 -  This project is an expansion from another project from this website.  On the one side you can read the RC5, RC5X and RC6 codes from remote controls on a LCD and on the other hand you can send all thinkable RC5, RC5X and RC6 codes to a device.  Besides is for this project a PCB layout drew to make it still more easier for you.  

Universal-3v-LED-Flasher -  The circuit below will flash any LED color with fixed current pulses powered by a 3v battery.  It uses a charge pump approach, which routes a constant current pulse through the LED, regardless of the LED voltage requirement.  Using this approach, white and. . . Circuit by David A. Johnson P.E.-June, 2008

Up/Down Ramping Light Pushbutton Control -  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 David A. Johnson P.E.-March, 2009

USB-Powered PC Lamp -  This white LED lamp lets you use your PC or laptop at night without disturbing others’ sleep.  It produces a soft white light just enough to see the keyboard in darkness...__ Electronics Projects for You

Use a Photoelectric-FET Optocoupler as a Linear Voltage-Controlled Potentiometer -  01/19/12 EDN-Design Ideas The circuit takes advantage of an identical photo-FET as a feedback element.  You can use a photoelectric FET as a variable resistor or a potentiometer in combination with a fixed resistor.  The H11F3M photoelectric FET has an isolation voltage of 7.5 kV, enabling you to safely control highvoltage circuit parameters.  The nonlinear-transfer characteristics of these devices are problematic, however (Figure 1).  To correct the nonlinearity, using a simple feedback mechanism as a potentiometer yields a linear response (Figure 2).  This circuit uses two photoelectric FETs—one for feedback and the other for applications requiring an isolated potentiometer.  You connect the inputs of the two photoelectric FETs in series to ensure the same amount of current for the input LEDs.   __ Circuit Design by Sajjad Haidar, University of British Columbia, Vancouver, BC, Canada

Use a switching-regulator controller to generate fast pulses -  04/13/06  EDN-Design Ideas Switching-regulator-controller ICs can deliver gate-drive pulses with rise and fall times of less than 2 nsec, making them ideal candidates for laboratory pulse-generators __ Circuit Design by Mitchell Lee, Linear Technology Corp

Use a Transistor as a Heater -  04/19/12  EDN-Design Ideas A temperature sensor and a hot transistor hold biological samples at a preset temperature.  It is common to use transistors for driving resistive heating elements.  However, you can use the heat that a power transistor dissipates to advantage in several situations, eliminating the need for a separate heating element because most transistors can safely operate at temperatures as high as 100°C.  A typical example is in a biological laboratory, in which the need for maintaining the temperature of samples in microliter-sized cuvettes is a common requirement.   __ Circuit Design by REC Johnson, B Lora Narayana, and Devender Sundi, Center for Cellular and Molecular Biology, Hyderabad, India

Use an Integrator Instead of Coupling Capacitors -  02/16/12  EDN-Design Ideas Level-shift a signal with an unknown dc offset to a known offset without ac coupling.  An ultrasonic sensor circuit requiring self-adjustment to the level of an ac-input signal also must accommodate the signal’s unknown and variable dc-bias voltage.  The circuit cannot use an ac coupling capacitor, and the resulting output must be level-shifted to a known dc offset.  The design uses a dc-offset compensator (Figure 1).   __ Circuit Design by Vladimir Rentyuk, Modul-98 Ltd, Zaporozhye, Ukraine

Use Thermoelectric Coolers with Real-World Heat Sinks -  04/17/08  EDN-Design Ideas When using a Peltier thermoelectric cooler with a less-than-perfect heat sink, you must derate the maximum voltage and current applied to the cooler __ Circuit Design by W Stephen Woodward, Chapel Hill, NC

Using a Light Dimmer IC for AC Motor Speed Control -  This circuit example uses LS7231 Light Dimmer IC__ LSI Computer Systems

UV light Box -  I have been making PCBs for quite a number of years but one om my material suppliers has recently changed the Photoresist spray ingredients and it can no-longer be used with "high-spectrum visible light.  This means I am now forced to have a UV-light box.  I therefore built mine and the moment it is a "lashup" fixed to the workbench with masking tape.  So please excuse me if I do not include a photograph __ Designed by Harry Lythall-SM0VPO

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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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