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 25µV 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. Design by W DIJKSTRA, WAALRE, THE NETHERLANDS
Fleapower Flasher Draws Less Than 50 µA - 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 Design by Gary Butterfield, IEC Electronics Technology Center, Newark, NY
FleaPower Oscillator Consumes only 1 µA - 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 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. 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 LT®8610 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 2.5µA 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 |