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Clock Circuits
Clocks:   #-A      B-C      D-G       H-O      P-S      T-Z


Last Updated on: Friday, August 21, 2015 06:59 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.,  12/14/02]

  • 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.,  11/14/10] 

  • 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.,  04/11/10] 

  • 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.,  11/14/10] 

  • 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.,  02/01/07]

  • 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.,  02/23/99]


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

100 MHz Clock Solution for Desktop Computers -  Application Brief # 021. . .  [Pericom Semiconductor]

 

13 GHz Frequency Counter Prescaler -  Here is a fairly simple "divide-by-1000" circuit which was first designed by Zeljko Bozic, S52ZB, in a 2006 issue of VHF Communications Magazine. The idea of this project is to extend the range of older (and cheaper) frequency counters. You can often find 100 MHz frequency counters for as little as $20 at hamfests or eBay, and this simple circuit will extend their range up to at least 13 GHz. This version is based around a Hittite HMC363 divide-by-8 prescaler, a Fujitsu MB506 divide-by-64 prescaler, and a "divide-by-1. 953125" circuit using standard digital logic. The Hittite HMC363 front-end prescaler is good up to 13 GHz or so, and will do 15 GHz if you increase the input RF power a bit and minimize the prescaler's exposure time. . . .  [Green Bay Professional Packet Radio]

 

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. . . .  [© EFY Enterprises Pvt. Ltd. All rights reserved.]

1MV Offset Clock-Tunable Monolithic 5-Pole Lowpass Filter -  DN67 Design Notes (Linear Technology). . .  [Linear Technology]

 

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.,  12/14/02]

24 Second Shot Clock Circuit -  This is a circuit intended to be used in basketball shot clock. . .  [Milardo de Guzman]

 

28 LED Clock -  programmable clock Timer circuit that uses individual LEDs to indicate hours and minutes. . .  [Bill Bowden's website]

 

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.,  11/14/10]

 

30 Nanosecond Settling Time Measurement for a Precision Wideband Amplifier -  AN79 AN79 modifies methods presented in AN74, permitting verification of 30 nanosecond amplifier settling times to 0. 1% resolution. sampling-based technique used is detailed and results presented. Appendices cover oscilloscope overdrive issues, . . .  [Linear Technology]

 

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.,  04/11/10]

 

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.,  11/14/10]

 

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.,  02/01/07]

 

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.,  02/23/99]

 

68HC11 Read Encoder -  The encoder is connected to PORTA PA0 and PA1 --  The board must be in BOOTSTRAB MODE (tested with Loggyboard). . .  [Ludwig Orgler-Fachingenieur Elektrotechnik]

 

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) . . .  [Circuit 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. . .  [Bill Bowden]

 

74ACT74 makes low-skeW clock divider -  12/17/98 EDN Design Idea   (File contains many circuits. Scroll to find this one. )  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. . . .  [by Tom Napier, Consultant, North Wales, PA]

 

7-segments 12/24 Hours LED clock with PIC 16F84A or 16F628A -  Almost No Parts Microcontroller based electronic circuit. . .  [from Jos Pino's Projects & Tidbits]

 

8 Hints for Making Better RF Counter Measurements 5967-6038e -  Application Note. . .  [Aligent]

 

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