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Timers and Counters Circuits

Timers & Counters:  #'s - A      B - D      E - L      M - S      T - Z

 

Last Updated: November 30, 2017 10:28 AM

Circuits Designed by Dave Johnson, P.E. :

 
2 Transistor Oscillators -  This page has two unusual two-transistor oscillators.  I set the component values for a low frequency application.  Both circuits draw only about 1 micro amp of current. . . Circuit by David Johnson P.E.-December, 2002

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 David Johnson P.E.-November, 2010

36-Hour Watchdog Timer -  A watchdog timer is often used in computer systems to detect when a computer is hung up and is no longer running properly.  If it does become locked up and is not able to supply a reset pulse to the circuit within a defined time frame the timer times out a. . . Circuit by David Johnson P.E.-April, 2010

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.-December, 2011

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 David Johnson P.E.-November, 2010

555 Timer Forms Simple Circuit 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 Dave Johnson P.E.-February, 2007

60hz Clock Generator is Line Powered -  This circuit is connected to the 120vac power line and transfers 60Hz clock pulses to a logic circuit.  The optoisolator used provides 5000 volts of isolation between the power line and the logic side of the circuit . . . Hobby Circuit designed by Dave Johnson P.E.-February, 1999

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 Johnson P.E.-September, 2010

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 Dave Johnson P.E.-May, 2012

 

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-368-7747




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

 

 
A Digital Timer for Less than $20 -  Just "nick" the timer from an old microwave oven and fit it into a case.  The resulting timer has lots of uses.__ SiliconChip

A French Revolutionary Clock -  December 16, 2015   if you run a search online, you will discover so-called metric or decimal clocks for sale.  But be careful -- these clocks have what looks like a metric face (10 hour markings and numbering) , but use a standard 12-hour mechanism, with 60 seconds per hour and 60 seconds per minute.  Such a clock is not a metric clock at all. __  Gadget Freak-Case #275

A GPS Module for Your PC -  Link it to your PC and trace your position on and on-screen map.  There's lots of freeware and shareware to use with it as well.__ SiliconChip

A GPS Receiver Based Frequency Standard -  Frequency accuracy has been a topic of special interest to many amateurs and experimenters since the early days of radio.  Until recently, the best frequency standard available to most hams was a crystal oscillator carefully adjusted to zero-beat __ Designed by Brooks Shera, W5OJM

A GPS-Synchronised Clock -  Tired of resetting the time on your wall clock? This GPS circuit will convert a standard battery wall clock into a precision timekeeper that never needs to be corrected.  it will even automatically adjust for daylight saving time.__ SiliconChip

A Lap Counter for Swimming Pools -  Do you swim laps to keep in shape? This simple Picaxe-powered counter will keep track of the number of laps you've done__ SiliconChip

A Little More Serious Frequency Meter -  Maximum input frequency is specified to be 30 MHz in the multi-chip configuration, and in single-chip configuration, there are both 5 MHz and 10 Mhz versions operating with 10 and 20 MHz crystals, respectively.  All versions have 9 1/2 digit resolution.  I have used __ Designed by Dick Cappels

A Morse Clock-Look Mum, No Hands! -  if you want to know the time, you've got to learn Morse code.__ SiliconChip

A new PIC-based Flexitimer Mk.4 -  Here's a new and enhanced version of a very popular project: an easily-programmed low-cost electronic timer module.  it's compact, easy to build and offers a choice of either a single on period or continuous on/off cycling with independently programmable periods.__ SiliconChip

A PIC16F819 Dymoclock (also Demonstrates interfacing 30 LEDs to a PIC using only six I/O pins) -  Microcontroller based electronic circuit __ Designed by Bruno Gavand

A PIC16F84A Alarm Clock -  Microcontroller based electronic circuit__ Bruno Gavand

A Real Time Clock IC (DS1307) project using the PIC micro -  Making A Real Time Clock (RTC) is simple if you use a helper chip such as a DS1307 because you do not need to keep track of the length of each month or account for leap years.   __ Designed by John Main

A Regularly Repeating Interval Timer -  Timer Circuits:  This circuit has an adjustable output timer that will re-trigger at regular intervals.  The output period can be anything from a fraction of a second to half-an-hour or more - and it can be made to recur at regular intervals of anything from seconds to days and beyond.  __ Designed by Ron J.

A Timer Pulse Train Output -  Schematic only __ Designed by G.L. Chemelec

A Timer that has a 50% duty Cycle -  Here is a basic circuit using a dip switch to control all the variables of this IC .  it has a Delay of a Number of Seconds, as Determined by You.  Then it output goes Hot for a number of seconds, Then the Delay again, Hot Again, AND REPEATiNG.  Optionally, instead of using the switch, you can take off wires to additional logic circuits. __ Designed by G.L. Chemelec

A Timer that is Useful for Repetitive Triggering -  it has a Delay of a Number of Seconds, as Determined by You.  Then it output goes Hot.  A Mosfet can be Added as shown to drive more Current.  Useful Examples of this circuit: Flashing a Camera for sequential time shots.  Or turning on a Sprinkler every 24 hours. __ Designed by G.L. Chemelec

A universal XCO/PLL Board that replaces crystal oscillator Modules -  The circuit is straightforward.  it may be equipped with the NB3N501, NB3N502 or NB3N511 from ONSEMi.  As we wanted to use parts not smaller than 1206, the formfactor is 'slightly' larger than the xco in it's DiL-14 case.  Therefore assembly can be done without the help of a microscope.  With three jumpers, all different frequency options are covered.  if necessary, a voltage regulator may be assembled as well.  The pcb is single sided, i.e.  the bottom layer is ground.  One bridge (wired) at the bottom was unavoideable. __ Designed by Alexander C. Frank, aka Ajarn Changpuak

AC Power Line Clock Controller using AT89C2051 -  The Clock Controller V1.1was designed to be an exemplary of using 'C' language to control timer0interrupt, 7-segment LED and keypad scanning.  it provides 1-bit sink currentdriving output, for driving a relay, opto-TRIAC, say.  Many projects requiring7-segment display and keypad interfacing may get the idea from the Clockcircuit and software.   __ Designed by Wichit Sirichote

AC Power Monitor -  This AC Power Monitor continuously watches the AC power line voltage for both under-voltage and missing cycles.  When it detects a total of 5 or 6 consecutive missing half-cycles (50mS, 50/60HZ) , it drops a relay and starts a timer.  A power contactor is slaved to the relay contacts.  its purpose is to protect power-loss __ Designed by Jim Keith

Accurate Electronic Stopwatch -  Here is a simple circuit which can be used as an accurate stop-watch to count up to 100 seconds with a resolution of 0.01 second or up to 1000 seconds with...__ Electronics Projects for You

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 Johnson P.E.-September, 2010

Achieve Simple Circuit IR data transmission from a PC’s serial port -  10/11/07 EDN Design Ideas:  By transmitting appropriate hex values from a PC's serial port to a pair of IR LEDs, a remote-control IR receiver can enable 38.4-kHz data transmission __ Circuit Design by Andreas Grün, Wedemark, Germany

Acquisition system is Programmable on the fly -  12-Oct-95 EDN Design Ideas:  The programmable data-acquisition system in Fig 1 can take 333k samples/sec using a 3-�sec sampling ADC, IC 3.  Multiplexer IC 1 and programmable gain amplifier (PGA] IC 2  provide four truly differential channels and four decade gains of 1, 10, 100, and 1000.  These features allow the circuit to handle low-signal sensors without additional conditioning circuitry.  The circuit does not require __ Circuit Design by Sergey Velichko, SCP, Boise, ID

Active High Trigger -  This circuit produces a HiGH output via a HiGH trigger:__ 555-Timer

Active Low Power-On Reset Timer (1s POR) -  The LTC6995 provides a simple, accurate low frequency clock uniquely configurable for long duration power-on reset and watchdog timer applications.  in this example the LTC6995 combines an programmable oscillator with precision circuitry and logic to achieve an accurate 1 second POR.  This resistor-settable POR can be programmed__ Linear Technology/Analog Devices App Note, Jul 16th 2013

Active Low Trigger -  This circuit sits LOW and the output goes HiGH when the push-button is pressed.  When the normally-closed push button is pressed, it opens and the uncharged 1u will be pulled to nearly 0v rail via the 10k and this will take pin 2 LOW to make output pin 3 HiGH for the duration determined by the 22u and 100k.  if the push-switch stays open, the 1u will charge via the 100k and eventually the output of the 555 will go low__ 555-Timer

AD9852 DDS schematic -  Schematic Only__ 

Adaptive Lighting System for Automobiles -  When a vehicle is driven on the highway at night, it is required that light beam should be of high density and should illuminate the road at a distance sufficiently ahead.  However, when a vehicle coming in the opposite direction approaches the vehicle with a high-beam headlight, driver of that vehicle will experience a glare,  __ Designed by T.K. Hareendran

Adaptive Turbo Timer -  if your car's turbocharger has just been running, it is vital to allow the engine to idle for a few minutes before switching off.  This Adaptive Turbo Timer will do the job automatically.  it only operates when necessary and sets the idle time according to how hard you've driving.__ SiliconChip

Adjustable High/Low Frequency Sine wave generator -  This circuit uses the versatile MAX038 function generator.  Although in this circuit some of the advanced characteristics of this IC are disabled, you can generate Sine, Triangle, Square waves (adjusting A0 and A1 pins see datasheet on www.  maxim-ic.  com if you want other waves, use a switch __ Designed by Jonathan Filippi

Adjustable Timer -  This circuit starts timing when switched on.  A green LED lights to show that timing is in progress.  When the time period is over the green LED turns off, a red LED turns on and a bleeper sounds.  The time period is set by a variable resistor and it can be adjusted from 1 to 10 minutes (approximately).  it could be used to set a time limit when playing games or as an egg-timer in the kitchen __ Designed by John Hewes

Adjustable Timer with 555 IC -  The 555 adjustable timer circuit starts timing when switched on.  The green LED lights to show that timing is in progress.  When the time period is over the green LED turns OFF, the red LED turns ON and the beeper sounds.  The time period is set by adjusting the variable resistor.  it can be adjusted from 1 to 10 minutes (approximately) with the parts shown in the diagram.  You can mark the times on a scale drawn on the box.   __ Designed by Popescu Marian

AF variable frequency generator using 555 IC -  Ham Radio - Schematic __ Designed by Guy Roels ON6MU

All-Ears QSK Timing Generator -  in the world of amateur (ham) radio morse code communications, QSK refers to a method of operation where the transmitter and receiver are alternately active when the key is down or up.  QSK is also known as full break-in keying.  QSK operation allows the operator to hear what is happening on their frequency in the brief times between transmitting morse code dits and dahs.  The conversation can be quickly interrupted by the other station, or by a third station.  The sender also knows immediately if their signal is being interfered with. __ Designed by G. Forrest Cook

Amplifier Timer -  This circuit turns-off an amplifier or any other device when a low level audio signal fed to its input is absent for 15 minutes at least. 
Pushing P1 the device is switched-on feeding any appliance connected to SK1.  input audio signal is boosted and squared by IC 2 A & B and monitored by LED D4.   __ Contact IQ Technologies

Amplifiers perform precision divide-by-2 -  6-Mar-03 EDN Design Ideas:  Rotary encoder mates with digital potentiometer - The classic implementation of a voltage-halving circuit uses two equal-value resistors.  Using 1% resistors provide as a divider output with 2% accuracy.  For most applications, this performance is cost-effective andthan adequate.  However, when you need extreme precision, this approach requires correspondingly accurate resistors and can become expensive __ Circuit Design by Glen Brisebois and Jon Munson, Linear Technology Corp, Milpitas, CA

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Timers & Counters:  #'s - A      B - D      E - L      M - S      T - Z


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