555 Time Delay Relay Circuit

This time delay relay circuit is built with IC NE/SE555, produced by Intersil which contains a precision timer. Stability to temperature variations is 0.005 %/^oC. In the circuit diagram, the IC works as a monostable multivibrator. It is set by operating the key Dr1. With Dr2 you can reset the assembly any time you desire.

Time delay relay operation
Pin 3 provides (after setting) a positive rectangular pulse, whose amplitude is approximately equal to the 12V power supply voltage. This output should not be charged with more than 200 mA over a period of time.
Pulse width can be calculated with the formula:

t = (R2 + Rp1)*Cs1

In this formula t is in seconds if the R2 and Rp1 values are set in ohms and Cs1 is in Farads. Cs1 is the switched capacitor to potentiometer P1 by the S1 switch. Lighting time is set roughly in the decade with S1, while P1 serves to fine tune.

Time delay:
S1a = 0.1 … 1 s
S2b = 1 … 10 s
S2c = 10 … 100 s
S2d = 100 … 1000 s
S2e = 1000 … 10000 s

For the Reed relay, by whose contacts the lamp is connected and disconnected, the following conditions must be met: operating voltage does not exceed 12 volts and current draw is not greater than 200 mA. If Reed relay’s working voltage is below 12 volts, then you can connect a resistance Rx in series with the relay’s coil.
Eventually it can be used a triac in place of the Reed relay. In this case the gate is controlled by Rx (here Rx = 150 ohms).
You should to consider a proper insulation of the time delay relay installation and wiring.

Time delay relay circuit schematic

Electronics Lab Created By Muhammad Irfan

Electronics Lab Created By Muhammad Irfan

 

Traffic Light control

Picture of our Traffic Light Project

This Traffic Light Circuit can be used to control traffic on roads or in public places.In a Traffic light there are three different color bulb which are Green, Yellow/Amber and Red.

 This project uses  IC555 as Astable Multivibrator for rapid squire wave pulse generation. This clock pulse is feed to IC 4017 which is a Counter IC. In this counter IC, for every pulse fed to input pin-14, the High level output keeps shifting from D1 to D9 in cyclic order. See Circuit Diagram below.

At a time one output is higher (Positive) and other output pins of IC remains at low state.

The capacitor and resistor on pin 15 of IC4017 are used to reset the counter to zero (Red light ON) at initial power up.

Part Used:

IC = NE555 ( Timer IC) , IC CD4017 (Counter IC)

Diode = IN4007  6Pcs

POT = 470K

Resistance = 22K, 100K, 220 Ohms X 3Pcs

Capacitor = 0.1 Mfd, 1 Mfd, 10 Mfd.

9 Volt Battery with Snap

Switch, Wire, Clamp, PCB

Electronics Lab  Created By   Muhammad Irfan

50 555 Timer circuits

THE SIMPLEST 555 OSCILLATOR
The simplest 555 oscillator takes output pin 3 to capacitor C1 via  resistor R1.
When the circuit is turned on, C1 is uncharged and output pin 3 is HIGH. C1 charges via R1 and when Pin 6 detects 2/3 rail voltage, output pin 3 goes LOW. R1 now discharges capacitor C1 and when pin 2 detects 1/3 rail voltage, output pin 3 goes HIGH to repeat the cycle.
The amount of time when the output is HIGH is called the MARK and the time when the output is LOW is called the SPACE.
In the diagram, the mark is the same length as the space and this is called 1:1 or 50%:50%.
If a resistor and capacitor (or electrolytic) is placed on the output, the result is very similar to a sinewave.

C1 to POSITIVE RAIL 
C₁ can be connected to the positive rail. This is not normal practice, however it does work.
The output frequency changes when the capacitor is changed from the negative rail to the positive rail. Theoretically the frequency should not change, but it does, and that's why you have to check everything.  The frequency of operation in this arrangement is different to connecting the components via pin7 because pin3 does not go to full rail voltage or 0v. This means all the output frequencies are lower than those in the "555 Frequency Calculator."
The table shows the frequency for the capacitor connected to the 0v rail and 12v rail:

C1 to 0v rail			C1 to 12v rail
1k	1n	505kHz	1k	1n	255kHz
1k	10n	115kHz	1k	10n	130kHz
1k	100n	23kHz	1k	100n	16kHz
10k	1n	112kHz	10k	1n	128kHz
10k	10n	27kHz	10k	10n	16kHz
10k	100n	3700Hz	10k	100n	1600Hz

 

CHANGING THE MARK-SPACE RATIOThis ratio can be altered by adding a diode and resistor as shown in the following diagrams. In the first diagram, the 555 comes ON ("fires-up") with pin 3 low and pin 2 immediately detects this low and makes pin 3 HIGH. The 10n is quickly charged via the diode and 4k7 and this is why the MARK is "short." When the capacitor is 2/3Vcc, pin 6 detects a HIGH and the output of the 555 goes LOW. The 10n is discharged via the 33k and this creates the long-duration SPACE (LOW). The second diagram creates a long-duration HIGH:

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THE THREE BASIC 555 OSCILLATORSThe 3 basic 555 oscillators are shown in these circuits.
The basic points to remember are these:
Pin 7 goes LOW when pin 3 goes LOW.
Pin 6 detects a HIGH
Pin 2 detects a LOW
Pin 3 can be used instead of the supply-rail to deliver a HIGH and instead of pin 7 to deliver a LOW to the timing section made up of pins 2&6 and "C" and a timing resistor.

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HOW TO REMEMBER THE PINS:

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INSIDE THE 555 

Note: Pin 7 is "in phase" with output Pin 3 (both are low at the same time).
Pin 7 "shorts" to 0v via a transistor. It is pulled HIGH via R1.
Maximum supply voltage 16v - 18v
Current consumption approx 10mA
Output Current sink @5v = 5 - 50mA     @15v = 50mA
Output Current source @5v = 100mA     @15v = 200mA
Maximum operating frequency 300kHz - 500kHz

Faults with Chip:
Consumes about 10mA when sitting in circuit
Output voltage can be up to 2.5v less than rail voltage Output can be  0.5v to 1.5v above groundSources up to 200mA
Some chips sink only 50mA,  some will sink 200mA

A NE555 was tested at 1kHz, 12.75v rail and 39R load. The Results: 
Output voltage 0.5v low, 11.5v high at output current of 180mA The "test chip" performance was excellent.

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THE 555 PINS

Here is the identification for each pin:

When drawing a circuit diagram, always draw the 555 as a building block, as shown below with the pins in the following locations. This will help you instantly recognise the function of each pin: 


Pin 1 GROUND.  Connects to the 0v rail. Pin 2 TRIGGER. Detects 1/3 of rail voltage to make output HIGH. Pin 2 has control over pin 6. If pin 2 is LOW, and pin 6 LOW,  output goes and stays HIGH. If pin 6 HIGH, and pin 2 goes LOW, output goes LOW while pin 2 LOW. This pin has a very high impedance (about 10M) and will trigger with about 1uA.Pin 3 OUTPUT. (Pins 3 and 7 are "in phase.") Goes HIGH (about 2v less than rail) and LOW (about 0.5v above 0v rail) and will deliver up to 200mA.Pin 4 RESET. Internally connected HIGH via 100k. Must be taken below 0.8v to reset the chip. Pin 5 CONTROL. A voltage applied to this pin will vary the timing of the RC network (quite considerably).  Pin 6 THRESHOLD.  Detects 2/3 of rail voltage to make output LOW only if pin 2 is HIGH. This pin has a very high impedance (about 10M) and will trigger with about 1uA.Pin 7 DISCHARGE. Goes LOW when pin 6 detects 2/3 rail voltage but pin 2 must be HIGH. If pin 2 is HIGH, pin 6 can be HIGH or LOW and pin 7 remains LOW. Goes OPEN (HIGH) and stays HIGH when pin 2 detects 1/3 rail voltage (even as a LOW pulse) when pin 6 is LOW.  (Pins 7 and 3 are "in phase.") Pin 7 is equal to pin 3 but pin 7 does not go high - it goes OPEN.  But it goes LOW and will sink about 200mA. You can connect pin 7 to pin 3 to get a slightly better SINK capability from the chip.Pin 8 SUPPLY. Connects to the positive rail.

Electronics Lab Created by Muhammad Irfan 

Electronics Lab Created by Muhammad Irfan 

555 LED DIMMER Circuit

This circuit will adjust the brightness of one or more LEDs from 5% to 95%.



Electronics lab created by Muhammad Irfan 
Electronics lab created by Muhammad Irfan

555 Amplifier Circuit

The 555 can be used as an amplifier. It operates very similar to pulse-width modulation. The component values cause the 555 to oscillate at approx 66kHz and the speaker does not respond to this high frequency.  Instead it responds to the average CD value of the modulated output and demonstrates the concept of pulse-width modulation. The chip gets very hot and is only for brief demonstrations. 


Electronics Lab  created   By   Muhammad Irfan
Electronics Lab  created   By   Muhammad Irfan