NE555 Schema and Application

Brief History of the NE555:

The NE555 is an integrated circuit used to manage time (delay, etc. ...). It was created in 1970 by Hans R. Camenzind and marketed in 1971 by Signetics. Today, this component is still used because it is easy to use (ideal for educational purposes) and inexpensive. Today, the CMOS version of this circuit is used (such as the Motorola MC1455), however there have been many improvements and variations of the circuit. But despite the variations, all types are compatible with each other at the pin.

Many manufacturers realize this circuit under different names and here are a few:

Motorola -> MC1455
Fairchild -> NE555
Philips -> NE555D
Texas instruments -> SN52555
National -> LM555C

The main features of this component:

• Runs on supply voltages from 4.5V to 16V (TTL compatible).
• Frequency 2 MHz max.
• Temperature stability of 0.005% per ° C.
• Maximum current output of 200 mA.

1-b: Symbol, internal schema, pin:

I usually record the NE555 that way in my schemes (but there are other ways to present the pins ...)

Symbol of the NE555:

The NE555 actually contains about 23 transistors, 2 diodes and about 16 resistors which, when associated, make up this pattern (Fig. internal NE555)

Here is the pinout of the case of NE555:

Description of Pins:

1 - GND: Case earth.
2 - TRIG (trigger) control the output state. Starts the timer.
3 - OUT: Out of the box.
4 - RESET (RESET) Reset output signal. Stops the timer.
5 - CONT: (reference) voltage reference. (2 / 3 of VCC).
6 - THREE (threshold) control the output state. Signall the end of the timing when the voltage exceeds 2 / 3 of VCC
7 - DISCHE: (discharge) the capacitor discharge timing.
8 - VCC: Power of the housing.

1-c: Principle of operation (in brief):

The three internal resistance to make a bridge NE555 voltage divider that provides the tension 2 / 3 and 1 / 3 VCC, used as reference voltage for comparator 2.

Four cases before us:

1 - RESET is at a low level: The latch is reset and the output is low.
2 - TRIG "to 1 / 3 of VCC: the switch is enabled (SET) and the output is at a high level.
3 - THREE> to 2 / 3 VCC: the flip-flop is reset (RESET) and the output is low.
4 - THREE <2 / 3 VCC and TRIG> to 1 / 3 of VCC: The output retains its previous state.

Truth table:

2 - Erection of single solenoid:

Little explanation about the term shot:

Mounting monostable means that the output of the assembly remains at a logic level when nothing happens on its control input. But when we put a pulse on its control input, the output switches to the opposite logic state, for a predetermined time (T1).

Any example:

2-a: mount non re-triggerable monostable:

The output is '1 'for a time' t1 ', when applying a negative pulse on the entry.
The term 't1' is determined by R1 and C1, including the following formula:

When you do the math, keep in mind that the components have a certain tolerance (5% for resistors, capacitors 10% ...)

This assembly is not re-trigger because if during the time t1 there is a new input pulse, the time 't1' does not include zero.

2-a: mount-triggerable monostable re:

The difference with the mounting re-triggerable monostable non is that the pin 4 (reset) is connected to pin 2 (TRIG).

The output is '1 'for a time' t1 ', when applying a negative pulse on the entry.
The term 't1' is determined by R1 and C1, including the following formula:

When you do the math, keep in mind that the components have a certain tolerance (5% for resistors, capacitors 10% ...)

This assembly is re-triggered because if during the time 't1' there is new momentum in the entrance, the time t1 starts again.

3 - Erection of Astable:

Little explanation about the term astable:

We say that a signal is astable when it passes a permanent logic state '1 'to logic '0'.
Example: a square wave.

Assembly diagram of the NE555 in astable:




With this installation we will be able to generate niche which will change the frequency and the time t1 and t2 corresponding to the time the state high and low.

= Time to the low state =
= Time in the high state =


Therefore
frequency =

and therefore:
duty cycle =

When you do the math, keep in mind that the components have a certain tolerance (5% for resistors, capacitors 10% ...)

4 - Example of use: Blink two LEDs:

The assembly that I propose allows to flash two LEDs at a speed that is selected by turning a knob.
This circuit operates with a 9V battery.

4-a: Schematic of the assembly:

4-b: List of components:

4-c: Operation and explanations:

The NE555 is used in astable.
That is, it will provide us with a square wave 0V - 9V.

So when the output OUT will be at 9 V, the LED D2 will have a positive voltage at its terminals and will be lit, while the LED D1 is turned off for power in reverse.
By cons, if OUT is 0V, the LED D1 will have a positive voltage at its terminals and will be lit while the LED D2 will be powered off for reverse.

See how often can you flash the LEDs:

Recall the formula for the frequency for the NE555 in astable mounting:
frequency =
In the diagram, corresponds to the C1 C2 formulas!

For P1 = 0 (minimum):


For P1 = 50 Kohm (maximum):



So by varying the minimum of P1 at its maximum can be varied the frequency of blinking LEDs between 1.26 Hz (approximately) to 9.86 Hz (approximately).

I say "about" as capacitors and resistors have a tolerance value ...

 

Shema was based NE555:

Organ has a mini base NE555

This is a circuit to build a small organ.
When in the press of a button (S1 to S5), the integrated circuit NE555 generate a tone.
VR1 for adjusting the frequency interval.

Diagram

A simple detector dark

This is a simple detector circuit absence of any light source or detector just dark.
The circuit generates the sound in the dark and goes into silence in the light

schema

Flashing brake lights for car

This circuit is provided as a hobby project. The 555 timer IC is connected to operate in astable multivibrator.

This is a flashing circuit modified to turn on and off a bulb instead of LED. It will create a state of flashing brake lights while the brake is pressed. You can adjust the flash rate by varying the variable resistor VR1. You can increase the value of C1 for a slower rate of flashing of a maximum of once in 10 seconds.
Before using this assembly that it the check is legal in your country.

Protection speakers

Schema

This assembly is designed to protect the speakers of the annoying "pump" that occurs in some amplifiers during power up. The assembly is based on the popular NE555 integrated circuit.

When the circuit is powered, it provides the delayed activation of a relay which is connected to pin 3 through diode D2. The delay time can be adjusted by adjusting the potentiometer P1. You can further increase the delay by increasing the value of C1.

Circuit