One Shot Timer | 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

One – Shot Timer use IC NE555

This is digital circuit, It is One – Shot Timer make by IC 555.
Power supply 5-15V, Output pin 3, Input pin 2 Trigger input.
T = 1.1 RC

Be the first to comment - What do you think? Posted by admin - April 9, 2010 at 12:00 pm

Categories: Digital, Timer Tags: one shot monostable, one shot timer

Simple Monostable Multivibrator by IC CD4528

This the Simple Monostable Multivibrator circuit. That interesting by use IC CD4528 , be IC CMOS perform be Dual Monostable Multivibrator or One shot. When encourage at input make have a signal pecks at 2 output by have differently. Pulse duration and accuracy are determined by external timing components R1 and C1. Wide supply voltage range 3.0V to 18V. Separate reset available. Quiescent current e 5.0 nA/package (typ.) at 5.0 VDC.
Diode protection on all inputs. Triggerable from leading or trailing edge pulse. Capable of driving two low-power TTL loads or one. Low-power Schottky TTL load over the rated tempera-ture rang.