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MicroPower  Circuits
Low Power (flea power): #'s - K        L - R        S- Z
 

Last Updated: October 24, 2017 02:55 PM

Circuits Designed by Dave Johnson, P.E. :

Basement Remote Doorbell  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Battery Eliminator  If you use a 1.5v or a 3v battery powered MP3 player for long periods of time, you may get tired of constantly changing batteries.  Some older players do not work will NiMH
rechargeable batteries so changing out batteries can get expensive.  The circuit be. . . Circuit by Dave Johnson P.E.-June, 2005

Battery Free LED Flasher  LED flashers have been used for a wide variety of applications.  Some flasher units have been used in food and hardware stores, to draw attention to sale items and are often attached to boxes which dispense product discount coupons. . . Circuit by David Johnson P.E.-December, 2010

Battery-Powered Freezer Alarm  A typical freezer can contain hundreds of dollars with of food.  If the device becomes unplugged or if the door is left open too long, the food inside can quickly become spoiled.  The hobby circuit below is a battery powered alarm system, which is attached . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

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 A. Johnson P.E.-March, 2002

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 Dave Johnson P.E.-January, 2002

Charge Pump Efficiently Divides Supply Voltage  This circuit uses a few FETs and logic devices to down convert a DC voltage to about one half its value. . . Circuit by David A. Johnson P.E.-July, 2000

Cheap Low Power 3v 2hz Oscillator  This is yet another method to generate low frequency output pulses.  The circuit uses an inexpensive under-voltage monitor IC and a couple of cheap MOSFETs.  It could easily be modified to produce pulse frequencies from about one cycle per minute to a maxim . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

Circuit Eliminates 9v Battery  If you use 9v battery powered devices for long periods of time, you may get tired of constantly changing batteries.  The circuit below can be wired into any 9v battery powered device, drawing power from an external AC to DC power adapter.  I designed the c . . . Hobby Circuit designed by David Johnson P.E.-December, 2009

Circuit Forms Ideal Diode Function  This circuit uses a low power op amp and a p-channel FET to form a diode function with a very low 0.05 volt voltage drop.  With the selected FET, the circuit can handle up to 2 amps of current.  Higher currents are possible with a FET with a lower channel. . . Circuit by Dave Johnson P.E.-January, 2008

Clear Fluid Monitor  An optical technique seemed like the best choice for this application.  The simple circuit below works well but only when the light detector can be shielded from bright ambient light.  A visible red LED launches light pulses through the side of the clear tubing and emerges at the opposite side.  A phototransistor forms a light detector.  The circuit takes advantage of the lens effect from any clear fluid inside the tubing.  When there is only air in the tubing, the light scatters and spreads out quickly before it reaches the photo-transistorCircuit Solution by David Johnson P.E.-May, 2005

CMOS IC Flashes LED  Judging from the numerous references I have received, this electronic circuit, hobby circuit seems to be rather popular.  Many published circuits which flash LEDs need 3 or more volts.  This electronic circuit uses only a single inexpensive C-MOS IC and . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

CMOS Oscillator, Draws Only 0.5ua  If truly low power oscillators interest you, this circuit draws a mere 2 microwatts (500nA) from a 6v battery.  It uses a very inexpensive C-MOS IC to produce a frequency of 2Hz.  However, by changing the component values you can push it to 300Hz . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Detector/Switch for Audio SignalFor some audio systems it is desirable to have an automatic switch circuit turn on other devices, such as an amplifier, if an audio signal is detected on one line.  The hobby circuit below will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal.  The switch could be used to turn on a relay, routing the signal to where it is needed.  A single 3v lithium cell will power the electronic circuit for about 5 years . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Detects Shadow Activated Motion  This circuit can sound an alarm when the shadow of a hand or arm moves over  two small photo diodes. . . Circuit by David A. Johnson P.E.-August, 2005

Door Knob Alarm  Many companies offer simple alarm devices for personal use in bedrooms or hotel rooms.  A metal chain attached to a box holding the electronics is placed around the inside doorknob of a wood door.  Anyone grabbing the knob from the outside is detected. . . Circuit by Dave Johnson P.E.-May, 2000

Door Knock Beeper  In some apartment buildings and homes, not equipped with a door bell, it may be hard to hear someone knocking on the front door.  The circuit below provides a means to activate a loud beeping sound inside, whenever someone knocks on the door. . . Circuit by David A. Johnson P.E.-June, 2009

Exciter Circuit-12v Touch Switch  This circuit generates a 20KHz pseudo sine wave signal that can power approximately 50 remote touch activated switch circuits.  This hobby circuit can support a cable length of approximately 2500 feet.  A typical remote switch circuit is also shown as . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2002

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.-March, 2002

Freeze Alarm  I chose an accurate thermistor from Keystone as the temperature sensor for this circuit.  This device has a very specific resistance at a particular temperature.  According to the data sheet for the thermistor, the device will have a resistance of 361K at zero degrees C, which is the freezing point of water.  The thermistor is wired into a simple bridge circuit, which uses 1% resistors.  The bridge is connected to a very low power voltage comparator.  The circuit forms a switch circuit, which changes state, when the resistance of the thermistor reaches a certain value.  At zero degrees C the voltage at the non-inverting input of the comparator exceeds . . . Circuit Solution by David A. Johnson P.E.-May, 2006

Freezer Over-Temperature AlarmThis circuit turns on a beeper whenever the inside temperature of a freezer is greater than zero degrees Centigrade.  The circuit draws only a few microamps from a 9 volt battery.  It uses a glass bead thermistor accurate to 1 degree C.. . . Circuit by David Johnson P.E.-November, 2014

Freezing Temperature Alarm  The circuit below is designed to activate a beeper alarm, whenever the outside air temperature is below 0 degrees C (32F).    A 9v battery powers the circuit.    The average 9ua current is so low that the battery should last for many years.. . . Circuit by David A. Johnson P.E.-November, 2014

High Ambient Light Immunity with a 40Khz Light Detector  The circuit below was designed to turn on an external 12v relay, whenever it detects light from a nearby LED light source, modulated at 40KHz to 50KHz.   This circuit was originally designed to operate from a fast moving vehicle . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

High Temperature Thermocouple activates Relay  Voltage from a high temperature thermocouple activates a relay when the sensor detects a temperature above 1000 degrees F . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Highly Stable Lower Power Oscillator  This circuit works much like the classic 555 timer, but draws only about 1.5 microamps from a 3 volt battery.  It is highly stable under varying temperature and supply voltages. . . . Hobby Circuit designed by Dave Johnson P.E.-May, 2000

Hour Meter triggered by Machine Vibration  This hobby circuit allows an off-the-shelf battery powered digital hour meter to be turned on and off, according to a machine's operation, without requiring a direct electrical connection to the machine . . . Hobby Circuit designed by Dave Johnson P.E.-January, 1998

Indicates Battery Charge Current  This circuit turns on a LED whenever it detects at least 25ma of battery charge current . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Infrared Safety Switch  Using a slotted optical sensor, this circuit can be used as a replacement for a large mushroom pushbutton safety switch. . . Circuit by David A. Johnson P.E.-July, 2006

Knocking rings Doorbell  In some apartment buildings and homes, not equipped with a door bell, it may be hard to hear someone knocking on the front door.  The circuit below provides a means to activate a loud beeping sound inside, whenever someone knocks on the door . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2009


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

Basement Remote Doorbell -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Battery Eliminator -  If you use a 1.5v or a 3v battery powered MP3 player for long periods of time, you may get tired of constantly changing batteries.  Some older players do not work will NiMH
rechargeable batteries so changing out batteries can get expensive.  The circuit be. . . Circuit by Dave Johnson P.E.-June, 2005

Battery Free LED Flasher -  LED flashers have been used for a wide variety of applications.  Some flasher units have been used in food and hardware stores, to draw attention to sale items and are often attached to boxes which dispense product discount coupons. . . Circuit by David Johnson P.E.-December, 2010

Battery-Powered Freezer Alarm -  A typical freezer can contain hundreds of dollars with of food.  If the device becomes unplugged or if the door is left open too long, the food inside can quickly become spoiled.  The hobby circuit below is a battery powered alarm system, which is attached . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

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 A. Johnson P.E.-March, 2002

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 Dave Johnson P.E.-January, 2002

Charge Pump Efficiently Divides Supply Voltage  -  This circuit uses a few FETs and logic devices to down convert a DC voltage to about one half its value. . . Circuit by David A. Johnson P.E.-July, 2000

Cheap Low Power 3v 2hz Oscillator -  This is yet another method to generate low frequency output pulses.  The circuit uses an inexpensive under-voltage monitor IC and a couple of cheap MOSFETs.  It could easily be modified to produce pulse frequencies from about one cycle per minute to a maxim . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

Circuit Eliminates 9v Battery -  If you use 9v battery powered devices for long periods of time, you may get tired of constantly changing batteries.  The circuit below can be wired into any 9v battery powered device, drawing power from an external AC to DC power adapter.  I designed the c . . . Hobby Circuit designed by David Johnson P.E.-December, 2009

Circuit Forms Ideal Diode Function -  This circuit uses a low power op amp and a p-channel FET to form a diode function with a very low 0.05 volt voltage drop.  With the selected FET, the circuit can handle up to 2 amps of current.  Higher currents are possible with a FET with a lower channel. . . Circuit by Dave Johnson P.E.-January, 2008

Clear Fluid Monitor -  An optical technique seemed like the best choice for this application.  The simple circuit below works well but only when the light detector can be shielded from bright ambient light.  A visible red LED launches light pulses through the side of the clear tubing and emerges at the opposite side.  A phototransistor forms a light detector.  The circuit takes advantage of the lens effect from any clear fluid inside the tubing.  When there is only air in the tubing, the light scatters and spreads out quickly before it reaches the phototransistor. . . Circuit Solution by David Johnson P.E.-May, 2005

CMOS IC Flashes LED -  Judging from the numerous references I have received, this electronic circuit, hobby circuit seems to be rather popular.  Many published circuits which flash LEDs need 3 or more volts.  This electronic circuit uses only a single inexpensive C-MOS IC and . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

CMOS Oscillator, Draws Only 0.5ua -  If truly low power oscillators interest you, this circuit draws a mere 2 microwatts  (500nA) from a 6v battery.  It uses a very inexpensive C-MOS IC to produce a frequency of 2Hz.  However, by changing the component values you can push it to 300Hz . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Detector/Switch for Audio Signal -  For some audio systems it is desirable to have an automatic switch circuit turn on other devices, such as an amplifier, if an audio signal is detected on one line.  The hobby circuit below will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal.  The switch could be used to turn on a relay, routing the signal to where it is needed.  A single 3v lithium cell will power the electronic circuit for about 5 years . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Detects Shadow Activated Motion -  This circuit can sound an alarm when the shadow of a hand or arm moves over  two small photo diodes. . . Circuit by David A. Johnson P.E.-August, 2005

Door Knob Alarm -  Many companies offer simple alarm devices for personal use in bedrooms or hotel rooms.  A metal chain attached to a box holding the electronics is placed around the inside doorknob of a wood door.  Anyone grabbing the knob from the outside is detected. . . Circuit by Dave Johnson P.E.-May, 2000

Door Knock Beeper -  In some apartment buildings and homes, not equipped with a door bell, it may be hard to hear someone knocking on the front door.  The circuit below provides a means to activate a loud beeping sound inside, whenever someone knocks on the door. . . Circuit by David A. Johnson P.E.-June, 2009

Dual 25V Micropower Op Amp Fits in 3mm X 3mm Package -  DN331 Design Notes__ Linear Technology/Analog Devices

Dual Micropower Comparator with Integrated 400MV Reference Simplifies Monitor & Control Functions -  DN321 Design Notes__ Linear Technology/Analog Devices

Exciter Circuit-12v Touch Switch -  This circuit generates a 20KHz pseudo sine wave signal that can power approximately 50 remote touch activated switch circuits.  This hobby circuit can support a cable length of approximately 2500 feet.  A typical remote switch circuit is also shown as . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2002

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.-March, 2002

Fleapower Detects shorts -  07/02/98 EDN-Design Ideas -  (File has several circuits, please scroll to find this one)  Sometimes, the need arises for a short-circuit tester that supplies a low current to the device under test  (DUT) and also uses voltages lower than 100 mV to prevent conduction of semiconductors.  The circuit in Figure 1 meets these requirements.  R1 limits the current in the DUT to 0.9 mA.  The voltage on the DUT can not exceed the value set by the ratio R2/ (R1+R2) .  The NE5230 micropower op amp compares the voltage on RX  (representing the DUT) with the voltage at the junction of R3 and R4.   __ Circuit Design by W DIJKSTRA, WAALRE, THE NETHERLANDS

Fleapower Flasher Draws Less Than 50 A -  01/23/03 EDN-Design Ideas Frequency source feeds entire labSome applications require a circuit to indicate that a battery's voltage has fallen below a certain value.  However, if you don't frequently check the indicator, the low-battery indicator itself can easily discharge the battery.  The circuit in Figure 1 indicates when the battery voltage has dropped below a preset value __ Circuit Design by Gary Butterfield, IEC Electronics Technology Center, Newark, NY

FleaPower Oscillator Consumes only 1 A -  05/21/98 Design Ideas -  (Multiple circuits listed, scroll to find this one)  A simple way to make an oscillator is to use a resistor, a capacitor, and a Schmitt trigger (Figure 1a].  However, this circuit uses several tens of microamperes because of the voltage transitions at the Schmitt trigger's input.  The CMOS device consumes almost no power when the input is either high or low.  Whenever the input voltage is at an intermediate __ Circuit Design by Yongping Xia, Teldata Inc, Los Angeles, CA

Freeze Alarm -  I chose an accurate thermistor from Keystone as the temperature sensor for this circuit.  This device has a very specific resistance at a particular temperature.  According to the data sheet for the thermistor, the device will have a resistance of 361K at zero degrees C, which is the freezing point of water.  The thermistor is wired into a simple bridge circuit, which uses 1% resistors.  The bridge is connected to a very low power voltage comparator.  The circuit forms a switch circuit, which changes state, when the resistance of the thermistor reaches a certain value.  At zero degrees C the voltage at the non-inverting input of the comparator exceedsCircuit Solution by David A. Johnson P.E.-May, 2006

Freezer Over-Temperature Alarm -  This circuit turns on a beeper whenever the inside temperature of a freezer is greater than zero degrees Centigrade.  The circuit draws only a few microamps from a 9 volt battery.  It uses a glass bead thermistor accurate to 1 degree C.. . . Circuit by David Johnson P.E.-November, 2014

Freezing Temperature Alarm -  The circuit below is designed to activate a beeper alarm, whenever the outside air temperature is below 0 degrees C  (32F) .    A 9v battery powers the circuit.    The average 9ua current is so low that the battery should last for many years.. . . Circuit by David A. Johnson P.E.-November, 2014

Gnat-power sawtooth oscillator works on Low supply voltages -  05/15/13  EDN-Design Ideas Making basic analog circuit functions that operate from a low-voltage battery supply can be tricky.  Lack of headroom and the need to minimize supply and leakage currents are usually the biggest challenges.   __ Circuit Design by Bruce D Moore, Consulting Analog Enginee

High Ambient Light Immunity with a 40Khz Light Detector -  The circuit below was designed to turn on an external 12v relay, whenever it detects light from a nearby LED light source, modulated at 40KHz to 50KHz.   This circuit was originally designed to operate from a fast moving vehicle . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

High Efficiency, UltraLow IQ, 42V, 2.5A Sync Buck Regulator -  The LT8610 step-down regulator integrates key high performance features in one compact IC.  It offers synchronous rectification, for efficiencies up to 96%.  The low quiescent current of 2.5A extends battery life and saves extra circuitry.  High speed switching minimizes board space and helps avoid EMI problems.  A low dropout __ Linear Technology/Analog Devices App Note, Leonard Shtargot Staff Engineer-Power Products Jun 14th 2012

High Temperature Thermocouple activates Relay -  Voltage from a high temperature thermocouple activates a relay when the sensor detects a temperature above 1000 degrees F . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Highly Stable Lower Power Oscillator -  This circuit works much like the classic 555 timer, but draws only about 1.5 microamps from a 3 volt battery.  It is highly stable under varying temperature and supply voltages. . . . Hobby Circuit designed by Dave Johnson P.E.-May, 2000

Hour Meter triggered by Machine Vibration -  This hobby circuit allows an off-the-shelf battery powered digital hour meter to be turned on and off, according to a machine's operation, without requiring a direct electrical connection to the machine . . . Hobby Circuit designed by Dave Johnson P.E.-January, 1998

Indicates Battery Charge Current -  This circuit turns on a LED whenever it detects at least 25ma of battery charge current . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Infrared Safety Switch -  Using a slotted optical sensor, this circuit can be used as a replacement for a large mushroom pushbutton safety switch. . . Circuit by David A. Johnson P.E.-July, 2006

Knocking rings Doorbell -  In some apartment buildings and homes, not equipped with a door bell, it may be hard to hear someone knocking on the front door.  The circuit below provides a means to activate a loud beeping sound inside, whenever someone knocks on the door . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2009

     >>>      This is the last page of #'sK

Low Power (flea power): #'s - K        L - R        S- Z

 


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