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Circuits designed by David Johnson, P.E.
Last Updated on: Thursday, April 07, 2016 02:04 PM

Master Category List - Dave's Circuits

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Control Circuits
Dave's Control Circuits, Page 1, Page 2, Page 3, Page 4, Page 5, Page 6, Page 7, Page 8

1 Watt Fluorescent Lamp Night Light  -  If you are tired of replacing small night light lamps, try this circuit. The line powered circuit uses a long life cold cathode fluorescent lamp. A simple charge pump technique runs the lamp without any transformer . . . [Circuit by Dave Johnson P.E.,  03/26/99]


1.5v LED Flasher Version A  -  Many published circuits that flash LEDs need 3 volts or more.  This circuit uses only a single inexpensive C-MOS IC and flashes the LED for a full year on a single 1.5 volt AA alkaline battery cell. The circuit uses a charge pump technique to provide . . . [Circuit by Dave Johnson P.E.,  06/04/00]


10 LED Sequential Flasher using Low Powr  -  A while back I posted a flasher circuit which flashed 10 LEDs sequentially.  That circuit was powered by four AA alkaline cells.  The circuit below operates much the same way but has been modified to run from a single 3v CR2032 lithium coin cell . . . [Circuit by Dave Johnson P.E.,  04/17/11]

12 Volt Lite/Dark Lamp Switch  -  Often, for certain low voltage lighting systems; you would like to turn off the lights during the bright light of the day.  Most commercial day/night switches are designed for AC lighting.  The circuit below was designed for a 12v DC system.  But, it could be modified for other voltage as well.  It uses an inexpensive phototransistor as the light detector. . . . [Hobby Circuit designed by David Johnson P.E.,  06/30/08]


120 VAC Low Voltage Alarm  -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac. . . . [Circuit by David Johnson P.E.,  07/09/06]


12v Brush Motor Speed Controller  -  In many applications, you would like to hold the speed of a motor constant, even as variations in the power supply voltage or mechanical load try to change its speed.  In other applications, the average current to the motor needs to be limited, so the . . . [Hobby Circuit designed by Dave Johnson P.E.,  05/05/07]


12v Cooling Fan Thermostat  -  This circuit will turn on a 12v DC powered cooling fan when the air temperature reaches a certain high temperature and will keep the fan turned on until the temperature drops below a second lower level.  Both the high and low temperatures are both adjustable . . . [Circuit by Dave Johnson P.E.,  02/06/11]


12v DC Motor with Logic Controlled Automatic Brake  -  There are times when you would like to control a DC motor using a simple +5v logic swing signal.  The circuit below performs this feat and also includes an automatic motor braking circuit.  When the input logic signal swings from 0v to +5v, the n-channel . . . [Hobby Circuit designed by David Johnson P.E.,  02/18/10]


12v Light/Dark Lamp Switch  -  At night, this circuit will route current to a 12v lamp, turning it on . . . [Circuit by Dave Johnson P.E.,  07/09/06]


14v LED AuxiliaryLamp with a 60 Watt Lamp  -  This circuit controls power to a standard 60 watt lamp plus generates an auxiliary 14v DC supply which can power an automotive style 12 LED array . . . [Hobby Circuit designed by David Johnson P.E.,  07/09/06]


1W White LED Night Light  -  As many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components.  This circuit is yet another version, which produces much more light than those other designs. . . . [Hobby Circuit designed by Dave Johnson P.E.,  11/06/08]


2 Pushbutton Motor Controller  -  Two small pushbutton switches, a few diodes and two relays form a method to control on/off power to a brush motor as well as the motor direction.  The circuit was originally designed for a motorized lifting platform . . . [Hobby Circuit designed by David Johnson P.E.,  09/11/05]


3 Minute LED Closet Light  -  The circuit below is powered by three 1.5v alkaline AA cells.  With a finger tap to the pushbutton trigger switch, a cluster of 6 wide angle white LEDs is turned on. The lights remain on for about 3 minutes, then will turn off.  The circuit’s standby current . . . [Hobby Circuit designed by Dave Johnson P.E.,  11/14/10]


3 Volt Low Battery Voltage Flasher  -  This circuit is designed to monitor two alkaline cells (3v) that form the battery often used in portable electronic equipment . . . [Circuit by David Johnson P.E.,  01/01/98]


3-Minute Closet Light  -  I have a coat closet by my front door.  The thing is very dark at night and really needs some kind of illumination inside.  I could hire an electrician to install a light in the closet ceiling and then wire it to a toggle switch outside the door but that would cost me quite a bit of money . . . [Circuit by David Johnson P.E.,  12/25/11]


3-Minute Closet Light #2  -  The circuit below is powered by three 1.5v alkaline AA cells.  With a finger tap to the pushbutton trigger switch, a cluster of 6 wide angle white LEDs is turned on. The lights remain on for about 3 minutes, then will turn off.  The circuit’s standby current is only a few microamps.  A set of fresh batteries should last at least 200 light applications.  The circuit uses a Schmitt trigger inverter and two transistors.  When the pushbutton switch S1 is pressed, the 10uF capacitor C1 is discharged . . . [Circuit by Dave Johnson P.E.,  11/14/10]


3v Powered Super Bright LED Flasher  -  I have posted several kinds of LED flashers over the years. This is yet one more flasher, designed to flash any high power LED of any color.  It hits the LED with a 25ms 250ma pulse once every 2 seconds. This works out to an average current about 3ma.  It . . . [Hobby Circuit designed by David Johnson P.E.,  04/22/09]


3v 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 . . . [Hobby Circuit designed by David Johnson P.E.,  07/11/06]


40Khz LED Test Signal Generator  -  This 40KHz crystal controlled oscillator circuit drives an infrared LED with powerful 40ma pulses.  The circuit can be used to test optical communications circuits, designed to receive 40KHz modulated light signals . . . [Circuit by Dave Johnson P.E.,  02/14/02]


40khz TV-VCR Light Source Repeater  -  This circuit is designed to be placed directly in front of a standard TV or VCR remote. The exiting light pulses produced by the circuit match the pulses from the remote but are about 10 times more powerful. Using the device, the remote can operate a TV or VCR over three times the normal distance . . . [Circuit by Dave Johnson P.E.,  06/04/00]


50ua Current Drives Solid State Relay Requires Only  -  Most solid state relays require at least 5ma and often more input control current, to fully turn on the device.  But such current levels often force battery powered circuits to use excessively large batteries.  The relay hobby circuit shown below demands only 50uA of input current . . . [Hobby Circuit designed by Dave Johnson P.E.,  06/03/00]


555 Timer Forms Simple PWM Motor Controller  -  Using a CMOS version of the 555 timer, this circuit can be used to control the speed of a motor by adjusting the duty cycle of the pulses sent to the motor . . . [Circuit by David Johnson P.E.,  02/01/07]


5w Fluorescent Lamp Intensity Modulator  -  The circuit was designed to experiment with using small fluorescent lamps as a broad pattern source of modulated light. The circuit hits the small lamp with narrow 1us pulses at a rate of 10KHz. Each pulse launches about 10 watts of visible light. The lamp . . . [Circuit by Dave Johnson P.E.,  06/27/00]


60 Watt Lamp With Auxiliary 14v LED Lamp  -  This circuit controls power to a standard 60 watt lamp plus generates an auxiliary 14v DC supply which can power an automotive style 12 LED array . . . [Circuit by Dave Johnson P.E.,  07/09/06]


6V to 24V DC Day/Night Switch  -  Using an inexpensive phototransistor, this circuit switches 12v to 24v power to a load, whenever the sun goes down . . . [Circuit by Dave Johnson P.E.,  07/09/06]


9v Powered Xenon Photoflash Controller  -  This 9v battery powered circuit is designed for remote control flash needs. A charge control circuit turns off the high voltage generator when the photoflash capacitor is fully charged. A neon lamp is included to indicate when the system is ready to flash . . . [Circuit by Dave Johnson P.E.,  06/03/00]


Dave's Control Circuits,
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Page 7, Page 8

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