http://www.next.gr/templates/cleancss/img/feed-esyndicat.pnghttp://www.next.gr/http://www.next.gr/meter-counter/clock-circuits/http://www.next.gr/meter-counter/clock-circuits/Oscillator-clock-generator-l13192.htmlThis self-starting fixed-frequency oscillator circuit gives excellent frequency stability. R1 and C 1 comprise the frequency-determining network, while R2 provides the regenerative feedback. Diode D 1 enhances the stability by compensating for the difference between VaH and VsurrLY· Tue, 26 Feb 2013 00:02:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Wide-frequency-ttl-clock-l13194.htmlThis free-running TTL square-wave oscillator has a variable frequency output over a 20:1 range or better through use of four of the six inverters in an SN7404 chip and the additional components shown. Frequency of oscillation is determined by the capacitor and the settings of potentiometers R2 and R4; the first pot controls width Tl and the second controls width T2 of the square-wave output. Tue, 22 Jan 2013 00:01:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Clock-Input-Frequency-Divider-l14067.html 1. THE INPUT CLOCK frequency fed into this circuit is divided by 2n-l. The circuit consists of clocked flip- Sat, 08 Sep 2012 00:09:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Glitch-free-turbo-circuit-l13293.htmlThis simple circuit generates a dual-speed clock for personal computers. The circuit synchronizes your asynchronous switch inputs with the master clock to provide glitch-free transitions from one clock speed to the other. The dual-speed clock allows some programs to run at the higher clock speed in order to execute more quickly. Other programs- for example, programs that use loops for timing-can still run at the lower speed as necessary. The circuit will work with any master-clock frequency that meets the flip-flops minimumpulse- width specs. Wed, 22 Aug 2012 00:08:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Single-op-amp-clock-l13193.htmlCapacitor C1 is charged through timing resistor R1 when the clock output is high. When C1 reaches the upper threshold voltage, the output signal decreases, and then C1 discharges through R1 until its voltage reaches the lower threshold point. When this happens, the output increases again and the cycle repeats itself. Using the parts values shown results in a frequency of 1 Hz. Sun, 22 Jul 2012 00:07:00 MSThttp://www.next.gr/meter-counter/clock-circuits/20Mhz-clock-phase-lock-l13214.htmlThe 20-MHz clock phase-locks to Apple"s Mac II 10-MHz NuBus clock. It uses a simple, inexpensive CMOS circuitry to generate 10-and 20-MHz square waves. The output duty cycle settings are insensitive to Vee variations. The input to the circuit is a NuBus clock signal with specifications that call for a 75 percent duty cycle at 10 MHz-a square wave that"s high for 75 ns and low for the remaining 25 ns. Sat, 14 Jul 2012 00:07:00 MSThttp://www.next.gr/meter-counter/clock-circuits/7-Segment-LED-Counter-l2333.htmlThis 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). Sat, 23 Mar 2013 00:03:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Propeller-Clock-Mechanically-Scanned-LED-Clock-l2341.htmlA 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. Wed, 06 Mar 2013 00:03:00 MSThttp://www.next.gr/meter-counter/clock-circuits/AVR-Microcontroller-Digital-Clock-with-ATtiny2313-l6300.htmlUsually we see Digital clock on LCD or 7 segmen. But, this AVR Digital Clock which is designed by Ficara Emilio displayed on Oscilloscope. The project use ATtiny 2313 as the main controller. What an interesting microcontroller project. Source code and schematic available for download.. Sat, 02 Mar 2013 00:03:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Don-t-let-slow-circuits-slow-down-the-system-l2360.htmlA combinatorial function with a propagation delay greater than the system clock period does not necessarily prevent a design from operating at frequency. By taking advantage of arrival times or carefully using wait states, a design can give the combinatorial circuit sufficient time to settle before sampling the output, thereby allowing the remaining logic to operate at frequency. Tue, 26 Feb 2013 00:02:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Quartz-Crystal-Windup-Wall-Clock-l8264.htmlLast year, I found a 31 day pendulum wall clock (dissambled) in a box of parts at a swap meet and decided to try and put it together and regulate it with a quartz crystal oscillator. The escapement part that rocks back and forth and drives the pendulum was missing and had to be made from a couple razor blade pieces and heavy copper wire. The razor blade escapement worked well but only allowed the movement to advance as the pendulum swung, and would not sustain the pendulum motion by itself. But this wasn't a problem since the quartz crystal divider circuit provides energy to the pendulum with an electromagnet to keep it swinging with only a 5 second error per day. Tue, 26 Feb 2013 00:02:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Bootstrapped-Timer-l5050.htmlThis circuit demonstrates how to use bootstrapping to seriously boost the output power of the timer. The LC555 can only put out about 50mA as it is. This circuit can put out at least 200mA and goes to the rail as well. Sun, 24 Feb 2013 00:02:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Pacer-clock-saves-subroutine-calls-l2371.htmlThis Design Idea outlines an easy-to-implement time-delay routine that requires no subroutine calls and thus avoids possible stack-overflow problems (Listing 1). This method also saves RAM space by requiring in most cases only two variables: the PACER_CLOCK as a free-running counter and another variable introduced at a particular instance (for example, TIME_VAR). Tue, 19 Feb 2013 00:02:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Clock-timer-with-LEDs-l8249.htmlThis is a programmable clock timer circuit that uses individual LEDs to indicate hours and minutes. 12 LEDs can be arranged in a circle to represent the 12 hours of a clock face and an additional 12 LEDs can be arranged in an outer circle to indicate 5 minute intervals within the hour. 4 additional LEDs are used to indicate 1 to 4 minutes of time within each 5 minute interval. Tue, 19 Feb 2013 00:02:00 MSThttp://www.next.gr/meter-counter/clock-circuits/SP-L-modulator-uses-single-speed-bit-clock-l2382.htmlSplit-level (SP-L), or Manchester, encoding is a common modulation scheme in data transmission (Figure 1). SP-L is popular because bit-clock extraction at the receiving end is easy, and the modulator circuit is simple to implement--simple, but not trivial, because the output of this classic circuit suffers from severe spikes during data transitions (Figure 2). Thu, 31 Jan 2013 00:01:00 MSThttp://www.next.gr/meter-counter/clock-circuits/More-accurate-PC-AT-clock-l2368.htmlThe combination of the 68k resistor and the capacitor provides a phase-shifted version of the AC input, so there is still 30-40V across the capacitor when the AC line goes through zero. When the downward zero crossing does occur, the 2N3904 turns off, the SCR`s gate goes positive, and the SCR fires, dumping the capacitor`s charge through the 4N27`s LED and pulling the output down to ground. Tue, 29 Jan 2013 00:01:00 MSThttp://www.next.gr/meter-counter/clock-circuits/simple-clock-dbler-l2337.htmlA week or 3 ago I posted a question about reccomendations for building a simple clock doubling circuit, to operate at approx 500kHz, using CMOS logic. The circuit functions quite well and is stable. If the Not gates are omitted, however, it becomes unstable, and gives variable width pulses. Mon, 28 Jan 2013 00:01:00 MSThttp://www.next.gr/meter-counter/clock-circuits/MSF-Radio-Time-Clock-l6855.htmlThe National Physics Laboratory broadcasts a time signal, previously known as the Rugby clock but now called "Time from NPL." Its most commonly known as the MSF signal due to it originally being identified in Morse code those letters. It is broadcast from Anthorn on 60kHz. Many commercial clocks use it to automatically set themselves. I decided to convert a digital clock I bought into one set by the MSF signal. To make the project more interesting I decided to use the ATtiny2313 microcontroller with only 2k flash ROM and 128 bytes of RAM. Features: Automatically set by MSF time signal. Bright, flicker free display. Alarm with choice of 5 polyphonic melodies. Hour chime with choice of melodies and no chime between 00:00 and 08:00 Tue, 22 Jan 2013 00:01:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Dynamic-clock-provides-for-zero-wait-states-l2361.htmlThe clock controller in Figure 1, which you can implement in a PLD, dynamically manipulates the timing of synchronous FIFO clock and control signals to provide for zero-wait-state accesses. These zero wait states would be otherwise impossible with a fixed clock design. This concept initially was developed for an embedded application that uses a RISC processor running at 25 MHz. Sun, 13 Jan 2013 00:01:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Use-a-PC-s-parallel-port-to-program-a-clock-source-l2386.htmlThis Design Idea shows how you can use Linear Technology`s LTC6903 programmable oscillator as a clock source for direct-digital synthesis, data conversion, switched-capacitor filtering, clock, and voltage-controlled oscillator circuits. Tue, 08 Jan 2013 00:01:00 MSThttp://www.next.gr/meter-counter/clock-circuits/28-LED-Clock-schematic-l8223.htmlIn the circuit below, 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 indicating the appropriate minute of the hour. Only two of the minutes shift registers are shown connected to 16 LEDs. Pin 13 of each register connects to pin 1 of the next for 7 registers. Fri, 28 Dec 2012 00:12:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Radio-Clock-for-PC-s-l2378.htmlThe three best known of these signals are the DCF77 signal broadcast from Mainflingen near Frankfurt in Germany on 77.5kHz which can be received through out most of central and northern europe. The MSF signal broadcast from outside Rugby in England by the National Physical Laboratory at 60kHz which can be received in the anywehere in the British Isles and large parts of northern europe. Sun, 23 Dec 2012 00:12:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Digital-Clock-with-6-nixies-l7232.htmlThe clock will have 6 digits and time setting will be done by means of a few buttons. I will try to use the most common types from widely used microcontroller families of miscellaneous producers. I will write the program in C language. Nixies need high voltage for operation. I wanted to avoid dangerous mains line voltage. The supply voltage for the clock must be safe 12 V. As the main target of the construction was toy, this instruction is not subtle construction with mechanical details and specified case. You can modify the clock to your taste and qualification. Most of blocks in the block diagram are clear. Somewhat special is converter TTL/high voltage for nixies. Anode drivers are based on high voltage NPN and PNP transistors. I took the driver here. TTL IC 74141 ensures BCD decoder and high voltage driver for individual digits. Sun, 23 Dec 2012 00:12:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Led-Clock-using-PIC16F84-l7395.htmlUsing only 2 capacitors, 3 resistors, 4 seven-segment Display, 1 xtal, 2 switches n.o. and 1 Microcontroller PIC, you can build this Digital Led Clock. you can use common anode or common cathode display, just select the display type. Here is the pinout information: Pin 3 defines the display type. If you will use common cathode display, connect to negative. For common anode, connect to positive. Here is a example circuit: Fri, 21 Dec 2012 00:12:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Use-a-system-s-real-time-clock-to-hide-a-code-sequence-l2387.htmlAlthough the concept of a totally accessible system represents an ideal situation for users, designers now must limit access toand conceal code sequences forsoftware routines for calibration, diagnostics, memory erasure, system reset, and more. In a system that includes a computer-compatible interface, such as an RS-232, a GPIB, or an infrared-I/O port, the system`s software can detect unique input patterns and execute the "secret" code sequences. Tue, 18 Dec 2012 00:12:00 MSThttp://www.next.gr/meter-counter/clock-circuits/digital-clock-circuit-l6135.htmlThe Clock Controller was 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. Thu, 13 Dec 2012 00:12:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Edge-detector-runs-off-of-single-supply-l2367.htmlYou can use a single-supply circuit to generate a pulse on both the rising and the falling edges of a signal for use with counters or similar devices that require only a rising edge to trigger (Figure 1a). R1 and C1 form a differentiator that converts rising edges to positive spikes and falling edges to negative spikes. Mon, 10 Dec 2012 00:12:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Digital-Clock-l7555.htmlThe digital clock of circuit, has as base one IC, the MM5314N, in which are contained all the circuits that need. The IC1 collaborates with six Display of common anode, that are not critically as materials. You can select what dimension, you want it is enough you adapt pins their in the circuit. The display are drive by a system of polyplexis and are drive by thirteen transistors. For timing the circuit, is used the frequency of network (50HZ). This solution is the simplest, that it is not best. For more constant frequency you can use a circuit that would be based on crystal, (it will be given shortly). For the clue of hour are used six display of 7 element common anode. The DS1-DS2, show the hours (decades-unit respectively), the DS3-DS4, show the minutes and DS5-DS6, the seconds. Sat, 08 Dec 2012 00:12:00 MSThttp://www.next.gr/meter-counter/clock-circuits/SPI-Interface-Big-7-Seg-LED-l2340.htmlThe 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. Thu, 06 Dec 2012 00:12:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Clock-circuit-using-SX-28-internal-oscillator-l6302.htmlThe SX 28 internal oscillator Is not that fast so an external oscillator can be hooked up to the processor as shown in the diagram to increase the operation cycles per second. Tue, 04 Dec 2012 00:12:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Clock-pulse-generator-for-CMOS-l7730.htmlExcellent clock generator to drive 4017 type cmos circuits. R1 = 10K to 10M, C1 = 100pF to 47uF. Fo is ±1Kz when R1=100K and C1=10nF. Input voltage can be from 5 to 15V. Sun, 02 Dec 2012 00:12:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Building-an-Intel-8008-Computer-Clock-l2342.htmlAbout every year I design and build a new clock. This years project is a clock based on an Intel 8008 first generation 8 bit microprocessor. Because it is a fairly unique project Im putting more effort into the documentation. Im also totally opening the design, hardware and software, to anyone wanting to learn more about the 8008. Tue, 06 Nov 2012 00:11:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Spinning-PIC-Clock-l2381.htmlThe idea is quite simple - spin a column of lights round in a circle fast enough, and you can scan out messages, rather like the scan on a television screen. With eight LEDs, a PIC and very few other components, you can create a simple display. The obvious choice for the message is the time, and so the Spinning PIC Clock is born. Tue, 06 Nov 2012 00:11:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Circuit-allows-high-speed-clock-multiplication-l2345.htmlIn theory, synchronous clock multiplication is an easy task. A simple PLL with two digital dividersone inserted just after the VCO (voltage-controlled oscillator) and the second one placed directly at the input of the phase detectormay do the job. The flexibility of such a configuration allows for clock multiplication by any rational number. Wed, 31 Oct 2012 00:10:00 MSThttp://www.next.gr/meter-counter/clock-circuits/19-LED-Clock-circuit-l8182.htmlThe clock circuit above uses seven ICs and 19 LEDs to indicate binary coded decimal time. The LEDs can be arranged (as shown in example above) so that each horizontal group of 3 or 4 LEDs represents a decimal digit between 0 and 9 and each individual LED represents a single bit or (binary digit) of the value. Binary digits have only two values (0 and 1) so a number written in binary would be something like 1001 or 0011, which represents decimal numbers 9 and 3 respectively. From right to left, each binary (1) represents increasing powers of 2, so that a 1 in the right hand place represents 2^0=1 and the next place to the left is 2^1=2 and then 2^2=4, and so forth. Sat, 20 Oct 2012 00:10:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Clock-switching-circuit-banishes-glitches-l2354.htmlMany of today`s digital systems require multiple clock domains as well as the ability to switch between them on the fly without producing glitches. Listing 1 consists of synthesizable VHDL code for such a circuit. In the circuit, two lines choose from among four input clocks to produce an output clock. Thu, 11 Oct 2012 00:10:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Clock-Calendar-Alarm-with-ATtiny12-l7005.htmlThis is the timekeeping test circuit. It includes a one-transistor circuit to switch in the 5V power supply when present and drop back to the 3v battery the rest of the time. That loop of blue wire-wrapping wire is a lariat used to quickly and easily pull the chip out of the socket during development without damage and without having to reach for the removal tool. Low current operation (chip sleeps most of the time). Alarm and external event triggered interpreter operation. Capable of stand-alone timer and alarm use. No additional processor required once programmed. One external input pin and one open drain output pin for interpreter. Mon, 08 Oct 2012 00:10:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Digital-Clock-Timer-schematic-l8265.htmlThis clock timer uses a PIC16F628 microcontroller to display 3 and 1/2 digit time and control an external load. The clock includes a calendar with leap year and optional daylight savings adjustments. The timer output can be set from 1 to 59 minutes and manually switched on and off. The clock also has a correction feature that allows an additional second to be added every so many hours to compensate for a slightly slow running oscillator. The oscillator uses a common 32.768 KHz watch crystal and the frequency can be adjusted slightly with the 24pF capacitor on the right side of the crystal. Fri, 05 Oct 2012 00:10:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Prop-Clock-Project-l2377.htmlThe LED`s are rotating at 1500rpm. The motor is an VCR head from a Sharp VC651SH it`s supplied with 12V 410mA The 1288 rpm (21Hz) is just enough for a stable picture. Thu, 04 Oct 2012 00:10:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Digital-Clock-with-Solar-Regulator-l8183.htmlThe basic clock circuit (top schematic below) is similar to the binary clock (on another page) and uses 7 ICs to produce the 20 digital bits for 12 hour time, plus AM and PM. A standard watch crystal oscillator (32,768) is used as the time base and is divided down to 1/2 half second by the 4020 binary counter. One half of a 4013 data latch is used to divide the 1/2 second signal by 2 and produce a one second pulse that drives the seconds counter (74HC390 colored purple). The minutes are advanced by decoding 60 seconds (40 + 20) and then resetting the seconds counter to 0 and at the same time advancing the minutes counter. The same procedure is used to advance the hours. The second half of the 4013 latch is used to indicate AM or PM and is toggled by decoding 13 hours and resetting the hours to 0 and then advancing the hours to "one". Wed, 03 Oct 2012 00:10:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Clock-fail-circuit-switches-to-alternate-clock-l2352.htmlA common design need is to detect the presence or absence of a clock signal. In the absence of a clock, it may be necessary to switch to an alternate clock or to at least notify the system that a failure has occurred. The circuit in Figure 1 uses a silicon delay line to anticipate when the next clock cycle is due and makes the flip-flop sample the input clock to verify that a pulse is present. Sun, 09 Sep 2012 00:09:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Scheme-speeds-access-to-uP-s-real-time-clock-l2380.htmlThe DS5000T (Dallas Semiconductors, www.dalsemi.com) is an 8051-compatible processor that integrates nonvolatile memory and a real-time clock. This module has an impressive set of functional extensions and security features, which makes it particularly useful for all-in-one embedded systems. Tue, 21 Aug 2012 00:08:00 MSThttp://www.next.gr/meter-counter/clock-circuits/PIC-Tock-l2373.htmlPIC-Tock is a video clock using a PIC16C61. In the tradition of Marv Newland`s "Bambi Meets Godzilla", there is far too much ROM space spent on credits, which are smooth-scrolled horizontally on the bottom of the screen. Sat, 18 Aug 2012 00:08:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Tanktwanger-circuit-puts-a-new-spin-on-clock-synthesis-l2384.htmlWhen you think of clock synthesis, you typically think of simple digital division or a PLL. However, using a wire delay line and an unusual circuit known as a "tanktwanger," you can produce a clock generator with numerous advantages, including phase that is continuously variable. Sat, 18 Aug 2012 00:08:00 MSThttp://www.next.gr/meter-counter/clock-circuits/System-implements-digital-clock-modulation-l2383.htmlThe original design used a VCXO (voltage-controlled crystal oscillator) for this function, but this revised design implements an all-digital method that provided additional functions, using a midlevel CPLD from Altera (www.altera.com). Fri, 17 Aug 2012 00:08:00 MSThttp://www.next.gr/meter-counter/clock-circuits/LCD-digital-Clock-using-PIC16F628-l7396.htmlThe reason why I'm using a LCD display is because it allow me to display many characters and it doesn't need to be "refreshed" as 7-segment Led displays. Also, the interface requieres less I/O pins. For this project I used a 16x1 LCD Display with 4-bits interface. Mon, 16 Jul 2012 00:07:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Programmable-Clock-Oscillator-l2375.htmlThis is a voltage controller oscillator that was designed as a wide range oscillator to generate clock pulses for a stepper motor drive system. It does however have some interesting features. The original application used a stepper motor for its ability to operate over a very wide speed range, so this oscillator is also designed for a very wide frequency range. Fri, 13 Jul 2012 00:07:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Programmable-divider-restores-SVGA-pixel-clock-l2376.htmlIf you`ve tried to design a video-overlay board that works with super- video- graphics- adapter (SVGA) graphics through a feature connector, you`ve probably noticed that the frequency of the supplied clock signal is not always equal to the pixel-clock frequency. In high-color modes (32,000, 64,000, and 16 million colors), the clock usually runs at 2 or 3½§ the pixel frequency. Mon, 09 Jul 2012 00:07:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Video-Clock-l7222.htmlThe LM1881 separates the composite sync signal from the incoming video. The 74HCT4538A one-shot eliminates the vertical sync and equalizing pulses, to provide a nice clean horizontal sync. (Yes, Elantec makes some chips that do this in one package.) A 16.1 MHz signal from the VCO of a 74HCT4046 PLL is phase locked to the horizontal sync via the 74HCT4020 configured to divide by 1024. That 16.1 MHz signal then serves as a clock for the PIC. The PIC in turn operates the 74HCT4051 multiplexer at just the right moments to put the clock pixels up in place of normal video. Having the PIC syncronous with the video signal allows crisp overlaying with no jaggies. Mon, 09 Jul 2012 00:07:00 MSThttp://www.next.gr/meter-counter/clock-circuits/VCXO-makes-inexpensive-dual-clock-reference-l2389.htmlThis Design Idea describes an inexpensive circuit to generate two extremely high-quality, crystal-clock-reference-signals, one of which is a PWM-controlled VCXO (voltage-controlled crystal oscillator) clock signal (Figure 1). Fri, 06 Jul 2012 00:07:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Delay-line-implements-clock-doubler-l2358.htmlTiming delays are undesirable in most digital circuits. However, in some cases, delays can be usefulto deal with a µP-speed-compatibility issue, for example. The circuit in Figure 1a uses a silicon T/4 delay line and an XOR gate to implement a simple clock doubler. Using a 5-nsec delay unit, a 50- MHz, 50% duty-cycle square-wave input produces a 100-MHz, 50% duty-cycle output clock. Sun, 01 Jul 2012 00:07:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Gated-clock-has-duty-cycle-control-l2363.htmlThe circuit in Figure 1 produces clock pulses with variable duty cycle from a gated clock. The output of the circuit, pulse, is always 180° out of phase with the clock input. When the delay-logic elements, IC5 and IC7, have the same propagation delays, the duty cycle of the circuit`s output is 50%. The circuit produces gated clock pulses when the gate input, gate, is high and the active-low reset, reset_n, is high. Sun, 17 Jun 2012 00:06:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Cheap-40KHz-clock-l2343.htmlThis circuit has worked for me in many applications. (it might be an idea to buffer the signal befor using it. (There are still 5 unused gates in the `C14.. :-) Sat, 16 Jun 2012 00:06:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Greenhouse-irrigation-controller-PIC16F84-l7373.htmlThis is a simple one-valve irrigation controller made for our greenhouse. The code contains a software real-time clock (RTC) and a multiplexed 8-digit LED display and keyboard you can use in other projects. The operating software is simple, it contains a real-time clock and a day counter. The valve is turned on in regular intervals in the same time. Day setting specifies the number of days between the activations, time setting specifies the time of the day when to start. Duration is the time after which the valve will be turned off. MODE button cycles through clock, start time and duration settings. the interval and starting time set will be stored in the DATA EEPROM. Scheduling can be totally turned OFF by the ENABLE button. Irrigation can be manually turned ON/OFF any time by the START/STOP buttons Fri, 15 Jun 2012 00:06:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Circuit-conditions-variable-duty-cycle-clock-l2346.htmlThe input-clock signal serves as the clock signal to a D flip-flop, which is configured as a toggle flip-flop. The flip-flop`s output signal is thus a 50%-duty-cycle, half-frequency version of the input clock, independent of the input-clock duty cycle. The flip-flop`s output passes through the clock-doubler circuit (from the earlier Design Idea, Figure 1b). Mon, 11 Jun 2012 00:06:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Gear-clock-using-PIC-16f628A-l8097.htmlThe heart of the clock is a PIC 16f628A microcontroller (PDF). This microcontroller has an internal oscillator however an external 20MHz crystal oscillator is being used since it will have to accurately keep track of time for weeks and months. The microcontroller is interfaced to two buttons and one motor. The interface is very simple, it consists of two buttons. When the left button is pressed the clock advances time using the motor. When the right button is pressed the clock decrements time using the motor. The only issue is when you need to correct time by many hours you would have to keep the button pressed for a long time. Wed, 06 Jun 2012 00:06:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Clock-recovery-scheme-suits-low-SNR-systems-l2353.htmlA clock-recovery architecture can operate with NRZ digital signals, even at low SNRs. A clock-recovery subsystem is based on a PLL comprising a phase comparator, a loop filter, and a voltage-controlled oscillator (VCO). Sat, 02 Jun 2012 00:06:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Video-Clock-Superimposer-l2390.htmlAs a followup to my VCR Pong project, here is a gadget that is actually useful in the Real World! It superimposes the time of day, in "HH MM SS" format, in the bottom right-hand corner of an existing video signal. My friend Scott uses it with his home security system. Fri, 01 Jun 2012 00:06:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Clock-using-a-Hard-Drive-l7101.htmlHave an old hard drive that no longer works? As long as it still spins up chances are you could build a clock out of your old hard drive! You will need some electronic knowledge, some common electronic components and a bit of patience. The clock that is produced isn’t exactly practical since most hard drives (especially older ones) are too loud for a clock that is to operate 24 hours a day. Uses 12 high power LEDs for displaying the clock hands, 6 Blue and 6 Red. Slot cut into upper drive platter and white tape on center drive platter provides a slot that when illuminated by the LEDs will represent a clock hand. Minute hand is represented by blue light, hour hand is represented by red light and the second hand is represented by purple (both blue and red on at the same time). Sun, 27 May 2012 00:05:00 MSThttp://www.next.gr/meter-counter/clock-circuits/74ACT74-makes-low-skew-clock-divider-l2335.htmlSerial-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. Sat, 26 May 2012 00:05:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Crosstalk-on-the-Clock-l2355.htmlWhat is the effect of crosstalk from the digital data signals into the clock signal of a data-conversion system? This is a more obscure problem than crosstalk from digital bits into the analog signal path, which was the subject discussed in the previous article: Part 1 of this series, Effects of Digital Crosstalk in Data Converters. Tue, 22 May 2012 00:05:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Clock-using-analogue-multimeters-PIC16F628A-l8098.htmlThe Multimeter Clock consists of three multimeters, the first meter displays hours, the second displays minutes and the last displays seconds. A 16F628A PIC microcontroller keeps track of time and outputs a calculated current to each meter to display the current time. The user enters the time by pressing three time adjust buttons. The first button increments the hours, the second button increments the minutes and the third button resets the seconds. Once the time has been entered the microcontroller will keep track of time from there. An interrupt fires every 10th of a second to increment a 10th second counter. Another routine checks to see if we have at least one full second of time, if we do the current time is incremented by a second. Thu, 17 May 2012 00:05:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Real-time-clock-chip-makes-low-power-oscillator-l2379.htmlMany systems use watch-crystal-based, 32.768-kHz oscillators. In battery-powered designs, the 32-kHz oscillator may consume a fairly high percentage of the total power budget. Reduced power consumption equates to longer battery life, smaller batteries, and smaller products. Sun, 13 May 2012 00:05:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Delay-line-has-wide-duty-cycle-range-l2357.htmlToday`s digital delay lines can process pulses no shorter than their delay times, and that restriction confines the devices to applications in which the duty cycle remains near 50%. A limited range of available delays (2 to 100 nsec per tap) further limits their use. Longer delay is available with one-shot multivibrators of standard digital-logic families, but those devices do not retain duty-cycle information. Sat, 12 May 2012 00:05:00 MSThttp://www.next.gr/meter-counter/clock-circuits/DC-power-wire-also-carries-clock-or-data-l2356.htmlDesigned for monitoring charge and discharge current in secondary batteries, IC1 outputs a current of 0.5 mA per amp of load current flowing through its internal sense resistor while rejecting common-mode supply-voltage noise. The on-chip sense resistor handles as much as 3A of continuous current. Thu, 10 May 2012 00:05:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Digital-Clock-circuit-with-CMOS-4047-l6301.htmlThis circuit provides a digital square wave that can be viewed directly or used to drive other circuits. It used the CMOS 4047 Low-Power Monostable/Astable Multivibrator. As used in Tom Duncan's Adventures with Digital Electronic's Book, to drive CMOS Decade of 4-bit binary counters. Thu, 03 May 2012 00:05:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Nixie-Clock-with-AVR-l7577.htmlThis was my second Nixie clock project. I wanted something a little smaller / cheaper / simpler then my rather large B-7971 clock. I will post the design for that one of these days. I was trying to simplify everything. And basically wound up with a one chip solution, ... the micro itself does just about everything. The Nixie tubes are relatively cheap and available (Ebay) Russian IN-17s. Discrete transistors drive the tubes in a 1x4 mux arrangement. Needs 15 I/O lines from the processor. No external RTC chip. Saw no need for 10 years backup with a lithium battery. Really just wanted a few hours to handle the typical short term power outages I get so I don't have to reset the time too often. Mon, 30 Apr 2012 00:04:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Nixie-Tube-Clock-l2370.htmlBecause of the nixie-tube is a gas tube, it requires relatively high-voltage supply. Judging from archives, from 180 to 300 volts are used for supply voltage. In this project, 270 volts from rectified 100V line voltage directly is used. It is very simple but whole of the circuit is not insurated from the power line, never touch any part of the circuit. Sun, 29 Apr 2012 00:04:00 MSThttp://www.next.gr/meter-counter/clock-circuits/Morse-Code-Alarm-Clock-l7081.html(Almost) Trivial application of an AT90S2313 or ATtiny2313 in an alarm clock to change the alarm from "BEEP BEEP BEEP BEEP BEEP BEEP BEEP BEEP..." to "WAKE UP" in Morse code. This was designed in response to a request and is in daily use. An inexpensive alarm clock was modified by installing a small circuit board inside the clock body and attaching some wires to the clock's circuit board. The second AA cell needed to bring the voltage up to 3 volts for the micro controller is mounted on the back. The high impedance speaker was temporarily mounted on the top as I pondered where the best permanent location would be, and like many decisions that are delayed with the aid of a temporary fix, its still waiting final disposition. Sat, 07 Apr 2012 00:04:00 MST