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Clock Circuits:   A - B      C - D      E - P      Q - Z


Last Updated: December 31, 2017 06:47 AM

Circuits Designed by  Dave Johnson, P.E.

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.-February 18, 2010

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 14, 2010

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.-February 18, 2010

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 14, 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 11, 2010

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 14, 2010

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 Dave Johnson P.E.-June 30, 2006

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 David Johnson P.E.-February 23, 1999

 

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

1-Gate Synchronizes Clock 10/27/94 EDN-Design Ideas -    The deceptively simple circuit in Fig 1 harbors formidable power.   Consider when you have a data-clock input to your system for an existing serial data stream.   Then, your system people surprise you __ by Phil Harvey, Technology Integration Inc/, Bedford, MA

1Hz Precision Clock Timer -  This timer makes an LED flash once every second along with a beep. The timing circuit uses a quartz crystal available in digital watches or clocks which generates precise frequency of 32.768 kHz. __ Designed by © EFY Enterprises Pvt. Ltd. All rights reserved.

1MV Offset Clock-Tunable Monolithic 5-Pole Lowpass Filter -  DN67 Design Notes (Linear Technology)___Linear Technology/Analog Devices

24 Second Shot Clock Circuit -  This is a circuit intended to be used in basketball shot clock__ Designed by Milardo de Guzman

28 LED Clock  -  programmable clock Timer circuit that uses individual LEDs to indicate hours and minutes__ Designed by Bill Bowden

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 14,2010

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 11,2010

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 14,2010

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 Dave Johnson P.E.-June 30,2006

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 David Johnson P.E.-February 23,1999

7 Segment LED Counter  -  This simple counter can be used to count pulses, as the basis for a customer counter (like you see at the doors of some stores) , or for anything else that may be counted. The circuit accepts any TTL compatible logic signal, and can be expanded easily (see Notes) __ Designed by Aaron Cake

72 LED Clock  -  in the circuit above, 60 individual LEDs are used to indicate the minutes of a clock and 12 LEDs indicate hours. The power supply and time base circuitry is the same as described in the 28 LED clock circuit above. The minutes section of the clock is comprised of eight 74HCT164 shift registers cascaded so that a single bit can be recirculated through the 60 stages i__ Designed by Bill Bowden

74ACT74 makes low-skew clock divider  -  12/17/98 EDN Design Ideas:     Serial-data systems often generate an internal clock at twice the data rate for mid-bit sampling or for generating bi-phase codes.   External equipment and some internal processes require a clock that runs at the data rate.   Simply dividing the twice-rate clock with a flip-flop generates a data-rate clock that is skewed by one logic delay with respect to the input.    This delay can be a significant fraction of the bit period.   You can use specialized PLL-based low-skew divider chips   Page includes several designs.    Scroll to find this one __ Circuit Design by JTom Napier, Consultant, North Wales, PA

7-segments 12/24 Hours LED clock with PIC 16F84A or 16F628A  -  Almost No Parts Microcontroller based electronic circuit__ Designed by Jos Pino's Projects & Tidbits

A 1MV Offset Clock-Tunable Monolithic 5-Pole Lowpass Filter  -  DN67 Design Notes (Linear Technology) __ Linear Technology/Analog Devices

A clock for all reasons, part 1: Monolithic oscillator invigorates instrumentation applications  -  06/26/03  EDN Technical Article: in addition to their common role as clock sources in digital systems, oscillators play an important role in instrumentation applications. A simple and tunable oscillator boosts the performance of a range of circuits. Part 1 of this series presents an RTD digitizer, thermistor-to-frequency converters, and relative-humidity digitizers.  __ Circuit Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

A clock for all reasons, part 2: Monolithic oscillator invigorates instrumentation applications  -  07/10/03  EDN Technical Article: Part 1 of this series presented a variety of circuits that use a monolithic oscillator in various applications. Part 2 continues with more examples: chopped amplifiers, sine-wave generators, an interval generator, and an ADC.  __ Circuit Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

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__ Designed by 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

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

AN-291: Asynchronous Clock Interfacing with the AD7878  -  AN-291 Analog Devices App Note__

AN-642: Coupling a Single-Ended Clock Source to the Differential Clock Input of Third-Generation TxDAC® & TxDAC+® Products  -  AN-642 Analog Devices App Note__

AN-769: Generating Multiple Clock Outputs from the AD9540  -  AN-769 Analog Devices App Note__

AT89C2051 Digital Thermometer & Clock  -  Build your own a laboratory instrument for measuring time and temperature. The DigiThermo demonstrates the use of 'C' language, a dual-slope converter, LCD interfacing, and digital filtering as well. __ Designed by Wichit Sirichote

Auto Snooze for Digital Alarm Clocks  -  Alarm clocks are made to wake you up. However, it is quite bothersome to hear the alarm continuously until you get up and put it off. Also, you might fall asleep again. The snooze facility solves this problem to some extent by allowing you to turn the alarm off for a specific period of time by pressing a switch. But here again, you need to look for the snooze switch!  __ Designed by © EFY Enterprises Pvt. Ltd. All rights reserved.

AVR Color Clock using RGB LEDs  -  This page describes a color clock that displays the time using two RGB LEDs, one for hours and one for minutes, showing time by using the standard color coding used for components (with two additional colors as the standard color coding only has ten colors and twelve is needed)  __ Designed by Rickard Gunee

Backup Clock Controller Checks Time Setting  -  01/05/95 EDN Design Ideas:  The simple, inexpensive circuit in Fig 1 provide as backup power to a clock IC during outages.  The circuit also determines whether the outage caused any loss in the time setting.  C1provide as the backup power, and the µC's ADC reads the time after the outage __ Circuit Design by David W Jordan, RL Drake Co, Franklin, OH

Big LED Clock  -  The circuit uses a serial-in-parallel out shift register, 74HC595 for receiving serial data from uController board. See example of U5 in the schematic, SER is for data input, SRCLK is shift clock and RCLK is Latch clock. Each data bit is shifted into the register on rising edge of the shift clock. When all data bits are shifted into the 8-bit register, the rising edge of RCLK will clock the data to be latched at each output bit, i.e. QA - QH.__ Designed by Wichit Sirichote

Binary clock  -  This clock displays the time in binary using discrete LEDs. The use of Flowcode [1] makes it very easy to program the PIC  controller in this project. The circuit is very simple. must register on this site__ Designed by Hans Summers

Binary clock using LED matrix to display a binary clock with 6 digits of 4 binary bits each  -  Timing and oscillator circuit diagrams / circuit schematics__ Designed by John Main

Bob Blick's Propeller Clock  -  A motor spins the "propeller", and a small microprocessor keeps track of time and changes the pattern on seven LEDs with exact timing to simulate a 7 by 30 array of LEDs.  It is an illusion, but it works nicely. __ Designed by Boblick

Build a synchronous clock  -  Synchronous clocks are still by far the most accurate currently available as (second-hand) consumer items. While it is certainly possible to make a quartz clock that is extremely accurate, very few manufacturers choose to do so. Because they are normally so cheap, most people would be unwilling to spend the extra to obtain guaranteed accuracy, and if such accuracy were needed, no off-the-shelf quartz clock would be good enough. __ Designed by Rod Elliott (ESP)

Building an Intel 8008 Computer Clock  -  About every year I design and build a new clock. This year’s project is a clock based on an intel 8008 first generation 8 bit microprocessor. Because it is a fairly unique project i’m putting more effort into the documentation__ Designed by Len Bayles


Clock Circuits:   A - B      C - D      E - P      Q - Z


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