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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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Circuits designed by David A. Johnson, P.E.:

Bistable Multivibrator or Flip/Flop Circuits
Bistable or Flip/Flops designed by Dave Johnosn
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1 Second One Shot Circuit  -  This timer circuit draws only 3ua of current, and can be powered by DC supplies ranging from 3v to 15v.  The circuit produces accurate pulses whose time can easily be adjusted, based on the R1 x C1 time constant.  The time should not change, . . . [Hobby Circuit designed by David A. Johnson P.E.,  09/02/10]


1.5V Touch Activated Switch  -  A single 1.5v silver oxide button cell powers this complete touch activated switch circuit for 5 years.  It features both a normally open and a normally closed set of solid-state switch thermals.  It also has an adjustable sensitivity, which can be set for a touch capacitance change as small as 1 picofarad. . . . [Circuit by David A. Johnson P.E.,  01/18/02]

12v Touch Switch Exciter Circuit  -  This circuit is designed to generate a 20KHz pseudo sine wave signal that can power about 50 remote touch activated switch circuits.  It can support a cable length of about 2500 feet.  A typical remote switch circuit is also shown as well as a receiver circuit for those switches. . . . [Circuit by David Johnson P.E.,  02/10/02]


3v Capacitance Proximity Switch  -  This circuit was designed to provide a touch activated switch function without an external power supply.  It draws so little power that a single 3v battery will operate the circuit for many years . . . [Circuit by David A. Johnson P.E.,  02/12/02]


Accurate One Shot Pulse Generator  -  This timer circuit draws only 3ua of current, and can be powered by DC supplies ranging from 3v to 15v.  The circuit produces accurate pulses whose time can easily be adjusted, based on the R1 x C1 time constant.  The time should not change, . . . [Circuit by David A. Johnson P.E.,  09/02/10]


Advertising Badge with Flashing LED #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 Dave Johnson P.E.,  03/26/02]


Advertising Badge with Flashing LED #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 Johnson P.E.,  03/26/02]


Automatic Timeout included with this On/Off Flip/flop Circuit  -  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 . . . [Hobby Circuit designed by David A. Johnson P.E.,  05/01/12]


Battery-Powered LED Flashing Advertising #2  -  This circuit is similar to flashing LED advertising badge #1.  It uses a CD4013 dual D Flip/Flop IC.  The 74HCT74 IC in #81 does not always work.  As in #81, a single lithium battery will provide months of continuous LED flashing. . . . [Hobby Circuit designed by David Johnson P.E.,  03/26/02]


Capacitance Proximity Switch-3 volts  -  This circuit was designed to provide a touch activated switch function without an external power supply.  It draws so little power that a single 3v battery will operate the circuit for many years . . . [Hobby Circuit designed by David A. Johnson P.E.,  02/12/02]


Capacitance Touch Switch  -  A single 1.5v silver oxide button cell powers this complete touch activated switch circuit for 5 years.  It features both a normally open and a normally closed set of solid state switch thermals.  It also has an adjustable sensitivity, which can be set . . . [Hobby Circuit designed by David Johnson P.E.,  01/18/02]


Darkroom Camera Shutter Timer  -  This circuit was designed to control a film exposure shutter for a darkroom. It has 8 time steps ranging from 0.35 seconds to 4 seconds. It is activated by a foot switch and draws power from an external 12-volt DC supply . . . [Circuit by David A. Johnson P.E.,  06/11/00]


Delayed Pulse Generator  -  This circuit generates a short 10ms pulse 15 minutes after a “start” pushbutton switch is activated . . . [Circuit by David A. Johnson P.E.,  10/16/05]


D-Flip/Flop One Shot 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.,  06/06/00]


Flashing LED Advertising 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 . . . [Hobby Circuit designed by Dave Johnson P.E.,  03/26/02]


Generate Short Delayed Pulse  -  This circuit generates a short 10ms pulse 15 minutes after a “start” pushbutton switch is activated . . . [Hobby Circuit designed by David Johnson P.E.,  10/16/05]


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.,  07/08/00]


Indicates when it is Time to Dust  -  I have used the circuit below for many different applications, which require ultra low power drain.  It uses a single CA4013 flip/flop.  One section forms a pulse generator.  The generator produces 100uS pulses at a rate of about 1 per second . . . [Circuit Solution by David Johnson P.E.,  05/07/06]


It's Time to Dust Indicator  -  I thought about this circuit when I heard that a lot cleaning personal in hotels were either dusting rooms more often than necessary or not enough. I have not yet built and tested this circuit completely but in concept it should work . . . [Hobby Circuit designed by David Johnson P.E.,  06/06/00]

Bistable or Flip/Flops designed by Dave Johnson
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Master Category List - Dave's Circuits


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