Digital Flip Flop | Electronic Project Circuits

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Multipurpose Flip-Flop Timer

This particular timing circuit can be used to time one-shot events from a few seconds to a few hours. And in standby mode (ie, with RLY1 and LED1 off), its power consumption is very low. The heart of this circuit is a low-cost CMOS 4011 quad NAND gate, with IC1a & IC1b configured as a standard Set/Reset flip-flop. Briefly pressing switch S1 to start the timing sequence pulls pin 1 of IC1a low and, as a result, pin 3 switches high. Two things happen while pin 3 is high: capacitor Cx begins charging via potentiometer Rx; and (2) pin 11 of IC1d will be low, which means that transistors Q3 and Q1 are both on.

As a result, both LED 1 and relay RLY1 are also on. RLY1 and LED 1 remain on until Cx has been charged up to about 70% of Vcc (ie, the supply rail). At this point, pins 8 & 9 of IC1c are pulled high and so its pin 10 output goes low and resets the flip-flop by applying a low to pin 6 of IC1b. This causes pin 3 of IC1a to go low and so LED1 and RLY1 switch off and the timing period ends. At the same time, pin 4 of the flip-flop goes high and this turns on transistor Q2 while ever the flip-flop is held reset. This ensures that Cx is discharged, so that the circuit is ready the next time S1 is pressed.
Diode D1 and its associated 10µF capacitor reset the flip-flop when power is first applied, so that LED1 and RLY1 remain off until S1 is pressed. D4 is included to protect Q1 against the back-EMF that’s generated when the relay switches off. Choosing appropriate values for Cx & Rx for a given time delay is straightforward. The formula is T = 1.24 x Rx x Cx, where T is the delay time in seconds. As an example, let’s assume that we require a time delay of 10s using a value of 100µF for Cx. Now we just need to calculate the value of Rx as follows:
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Author: Trent Jackson – Copyright: Silicon Chip Electronics
Source: http://www.extremecircuits.net/2010/06/multipurpose-flip-flop-timer_14.html

Be the first to comment - What do you think? Posted by admin - October 26, 2010 at 7:14 am

Categories: Digital Tags: digital flip flop, one shot timer

led display with nand gate digital control

This circuit operates in the digital circuit.It has 2 inputs are inputs inputs A and B inputs to receive input, By used nand gate ICs,To control the on-off of the lamp.

Operation of the circuit. When the input to the A is listed as “0″ or “1″.And B is listed as “0″ will cause the output of IC1 / 3 to “0″.The Q1 does not work will not light LED1.But if the A is listed as “0″ and B is listed as “1″ will cause the output of IC1 / 3 to “1″ As a result, Q1 LED1 light work.

But if the A is listed as “1″ and B is listed as “1″ will enable LED1 blinking frequency of approximately 3.5 Hz.The principle is working. The first two legs of the conditions IC1 / 1 “0″ to the output Into “1″.And IC1 / 2 off the output is “0″ IC1 / 3 to return to the status output from a “1″ LED1 is light.And caused a charge of C1.This will take and when will fully charge C1 pin 2 of IC1 / 1 is “1″ makes the output from “0″.And IC1 / 2 off the output is “1″ and IC1 / 3 to return to the status output from a “0″ LED1 is extinguished. And caused the discharge of C1 through the voltage of R2 through the voltage of C1 gradually decreased.The voltage at pin 2 of IC1 / 1 to 0 volts of this work will continue, causing LED1 flashes.

Be the first to comment - What do you think? Posted by admin - October 4, 2010 at 8:30 am

Categories: Digital Tags: digital control systems, digital flip flop, nand gate logic

12F675 as a D-type or JK-type flip flop

Since I implemented a D type flip flop using the PIC Logic Elements I thought I might go the other way and implement an entire D type flip flop in a single PIC. This uses the edge triggered and port change status interrupts and was an opportunity to have a play with interrupts on the PIC. As written this code will cause a PIC to function as a negative edge triggered D type flip flop with active low Set and Reset inputs.
Read Source: http://picprojects.org.uk/projects/picprojects.htm#12F675%20as%20D%20Type%20Flip%20Flop