The legendary NE555 timer - description and application of the chip. What practical circuits can be made on the NE555 timer Timer 555 rare circuits

We continue the review timer 555. In this article we will look at examples of the practical application of this microcircuit. The theoretical review can be read.

Example No. 1 - Darkness alarm.

The circuit beeps when darkness falls. While the photoresistor is illuminated, pin #4 is set low, which means the NE555 is in reset mode. But as soon as the lighting drops, the resistance of the photoresistor increases and a high level appears at pin No. 4 and, as a result, the timer starts, emitting a sound signal.

Example No. 2 - Alarm module.

The diagram represents one of the car alarm modules, which emits a signal when the vehicle's tilt angle changes. A mercury switch is used as a sensor. In the initial state, the sensor is not closed and the NE555 output is set low. When the angle of inclination of the car changes, a drop of mercury closes the contacts, and a low level at pin No. 2 starts the timer.

As a result, a high level appears at the output, which controls some actuator. Even after the sensor contacts open, the timer will still remain active. You can disable it by stopping the timer by applying a low level to pin No. 4. C1 is a ceramic capacitor with a capacity of 0.1 µF ().

Example #3 - Metronome.

A metronome is a device used by musicians. It counts the required rhythm, which can be adjusted with a variable resistor. The circuit is built according to the circuit of a rectangular pulse generator. The metronome frequency is determined by the RC circuit.

Example #4 - Timer.

Timer for 10 minutes. The timer is turned on by pressing the “Start” button, and the HL1 LED lights up. After the selected time interval has passed, the HL2 LED lights up. Using a variable resistor you can adjust the time interval.

Example No. 5 - Schmitt trigger on a 555 timer.

This is a very simple but effective scheme. The circuit allows, by applying a noisy analog signal to the input, to obtain a pure rectangular signal at the output

Example #6 - Precise generator.

Generator with increased accuracy and stability. The frequency is adjusted by resistor R1. Diodes - any germanium. You can also use Schottky diodes.

Read the continuation of “Using the NE555 timer - part 2.”

Watch video: Using the NE555 timer

Portable USB oscilloscope, 2 channels, 40 MHz....

Chip NE555(analogue of KR1006VI1) - a universal timer, designed to generate single and repeating pulses with stable time characteristics. It is not expensive and is widely used in various amateur radio circuits. It can be used to assemble various generators, modulators, converters, time relays, threshold devices and other electronic equipment components...

The microcircuit operates with a supply voltage from 5 V to 15 V. With a supply voltage of 5 V, the voltage levels at the outputs are compatible with TTL levels.

Dimensions for different types of housings

CASE - DIMENSIONS
PDIP (8) – 9.81 mm × 6.35 mm
SOP - (8) - 6.20 mm× 5.30 mm
TSSOP (8) – 3.00 mm× 4.40 mm
SOIC (8) – 4.90 mm× 3.91 mm

NE555 block diagram

Electrical characteristics

PARAMETER	TEST CONDITIONS		SE555			NA555 NE555 SA555			UNITS MEAS.
			MIN	TYP	MAX	MIN	TYP	MAX
Voltage level at THRES pin	V CC = 15 V		9.4	10	10.6	8.8	10	11.2	IN
	V CC = 5 V		2.7	3.3	4	2.4	3.3	4.2
Current (1) through THRES pin				30	250		30	250	nA
TRIG pin voltage level	V CC = 15 V		4.8	5	5.2	4.5	5	5.6	IN
		T A = –55°C to 125°C	3		6
	V CC = 5 V		1.45	1.67	1.9	1.1	1.67	2.2
		T A = –55°C to 125°C			1.9
Current through TRIG pin	at 0 V on TRIG			0.5	0.9		0.5	2	µA
Voltage level at the RESET pin			0.3	0.7	1	0.3	0.7	1	IN
	T A = –55°C to 125°C				1.1
Current through RESET pin	with V CC on RESET			0.1	0.4		0.1	0.4	mA
	at 0 V on RESET			–0.4	–1		–0.4	–1.5
Switching current on DISCH in closed state				20	100		20	100	nA
Switching voltage on DISCH in open state	V CC = 5 V, I O = 8 mA						0.15	0.4	IN
Voltage on CONT	V CC = 15 V		9.6	10	10.4	9	10	11	IN
		T A = –55°C to 125°C	9.6		10.4
	V CC = 5 V		2.9	3.3	3.8	2.6	3.3	4
		T A = –55°C to 125°C	2.9		3.8
Low output voltage	V CC = 15 V, I OL = 10 mA			0.1	0.15		0.1	0.25	IN
		T A = –55°C to 125°C			0.2
	V CC = 15 V, I OL = 50 mA			0.4	0.5		0.4	0.75
		T A = –55°C to 125°C			1
	V CC = 15 V, I OL = 100 mA			2	2.2		2	2.5
		T A = –55°C to 125°C			2.7
	V CC = 15 V, I OL = 200 mA			2.5			2.5
	V CC = 5 V, I OL = 3.5 mA	T A = –55°C to 125°C			0.35
	V CC = 5 V, I OL = 5 mA			0.1	0.2		0.1	0.35
		T A = –55°C to 125°C			0.8
	V CC = 5 V, I OL = 8 mA			0.15	0.25		0.15	0.4
High output voltage level	V CC = 15 V, I OH = –100 mA		13	13.3		12.75	13.3		IN
		T A = –55°C to 125°C	12
	V CC = 15 V, I OH = –200 mA			12.5			12.5
	V CC = 5 V, I OH = –100 mA		3	3.3		2.75	3.3
		T A = –55°C to 125°C	2
Current consumption		V CC = 15 V		10	12		10	15	mA
		V CC = 5 V		3	5		3	6
	Output low, no load	V CC = 15 V		9	10		9	13
		V CC = 5 V		2	4		2	5

(1) This parameter affects the maximum values ​​of timing resistors R A and R B in the circuit Fig. 12. For example, when V CC = 5 V R = R A + R B ≉ 3.4 MOhm, and for V CC = 15 V the maximum value is 10 mOhm.

Performance characteristics

PARAMETER		TEST CONDITIONS (2)	SE555			NA555 NE555 SA555			UNITS MEAS.
			MIN.	TYPE.	MAX.	MIN.	TYPE.	MAX.
Initial error time intervals (3)		T A = 25°C		0.5	1.5 (1)		1	3	%
				1.5			2.25
Temperature coefficient of time interval	Each timer, monostable (4)	T A = MIN to MAX		30	100 (1)		50		ppm/ °C
	Each timer, astable (5)			90			150
Changing the time interval depending on the supply voltage	Each timer, monostable (4)	T A = 25°C		0.05	0.2 (1)		0.1	0.5	%/V
	Each timer, astable (5)			0.15			0.3
Output pulse rise time		C L = 15 pF, T A = 25°C		100	200 (1)		100	300	ns
Output pulse decay time		C L = 15 pF, T A = 25°C		100	200 (1)		100	300	ns

(1) Conforms to MIL-PRF-38535 and has not been field tested.

(2) For conditions specified as Min. and Max. , use the appropriate value specified in the recommended operating conditions.

(3) The error of the time interval is defined as the difference between measured meaning and average value random sample from each process.

(4) Values ​​are for a monostable circuit with the following component values ​​R A = 2 kΩ to 100 kΩ, C = 0.1 μF.

(5) Values ​​are for an astable circuit with the following component values ​​R A = 1 kOhm to 100 kOhm, C = 0.1 µF.

Metal detector on one chip

Coil diameter 70-90 mm, 250-290 turns of wire in varnish insulation (PEL, PEV...), with a diameter of 0.2-0.4 mm.

Instead of a speaker, you can use headphones or a piezo emitter.

Video of this metal detector in action

Voltage converter from 12V to 24V

Toy animation

Together with counter 4017 and 555, you can make a “running fire” to animate some kind of toy or souvenir. When the power is turned on, the 555 generator starts running for just a few minutes, then turns off. At the same time, the current consumption drops - the batteries will last for a long time. The time is set with a 500 kOhm variable resistor.

Light controlled generator

Dark detector with LM555. This scheme will generate sound when light hits the Cds photo sensor. Sveta . When exposed to light, the sensor closes the circuit and the 555 generates oscillations around 1 kHz via open transistor BC158.

Musical keyboard

A very simple musical instrument (keyboard) for playing music can be made using a 555 chip. You can build an unusual musical instrument in the photo above. Graphite is used as a keyboard and a sheet of paper with notes is represented as holes in the paper.

The same circuit, but with ordinary resistors and buttons.

Timer for 10 minutes

The timer is started by button S1 after 10 minutes. LED1 and LED2 blink alternately. The time is set by a 550 kOhm resistor and a 150 µF capacitor.

Car alarm simulator

The LED flashes as if the car has an alarm. Install the LED in a visible place. The thief will see that the car is under alarm and will avoid it :)

A simple police siren simulator

The circuit is assembled on a breadboard.

Using two NE555s you can make a simple police siren generator. It is recommended that you make the following timer parameters: R1=68 kOhm (timer No. 1) is set to slow generation mode and the timer with R4=10 kOhm (timer No. 2) is set to fast generation mode. MYou can change the timer characteristics. The output frequency is changed by a chain of resistors R1, R2 and C1 for timer components No. 1 and R4, R5 and C3 for timer No. 2.

A similar circuit below with a transistor at the output:

Liquid Level Sound Generator

You can use this water level control circuit to alarm anywhere like level indicator water, such as in reservoirs, tanks, pools or anywhere else.

This is not all the capabilities of the timer chip. Also watch a video of the chip in action.

555 Timer IC is one of the most commonly used ICs among students and hobbyists. There are many applications of this IC, mainly used as vibrators, ASTABLE MULTIVIBRATOR, MONOSTABLE MULTIVIBRATOR and BISTABLE MULTIVIBRATOR. In this article, we will try to cover various aspects of 555 IC timer and explain its working in detail. So let's first define the concepts of what are astable, monostable and bistable vibrators.

ASTABLE MULTIVIBRATOR

This means that there will be no stable output level. So the output will fluctuate between high and low levels. These astable output parameters are used as a clock for a rectangular output for many applications.

SINGLE-STABLE MULTIVIBRATOR

This means that there will be one stable state and one unstable state. In steady state, the level can be selected high or low by the user. If the stabilized output is selected high, then the Timer always tries to set the output level high. Therefore, with a low level state, the Timer is turned off for a short time and this state is called unstable during this time. If stable, the minimum value is selected and the output interrupt goes high for a short time before the low value arrives.

[Read more about Monostable Multivibrator: 555 Timer Monostable Multivibrator Circuit]

BISTABLE MULTIVIBRATOR

This means the output state is stable. With each interruption the output changes and remains as is. For example, the output is considered high now, with a break it decreases and remains low. The next break he goes high.

[Read more about Bistable Multivibrator: 555 Timer IC Bistable Multivibrator Circuit]

Important Features of Timer IC 555

NE555 IC and 8 pin devices. The important electrical characteristics of the Timer are that it should not turn on above 15V, this means that the voltage source cannot be higher than 15V. Secondly, we can't draw more than 100mA from the chip. If you do not follow these steps, the chip will be burned or damaged.

Explanation of work

The timer mainly consists of two main structural elements and they are:

1. Comparators (two) or two op-amps

2.One SR multivibrator (trigger reset selection)

As shown above there are only two important components in a Timer, these are two comparators and a flip-flop. Need to understand what is a comparator and trigger.

it is simply a device that compares the voltage at the input terminals (inverting (-VE) and non-inverting (+VE)). Therefore, depending on the difference in the positive terminal and the negative terminal at the input to the port, the output of the comparator is determined.

For example, consider the positive input terminal voltage will be +5V and the negative input terminal will be +3V voltage. The difference is 5-3=+2V. Since the difference is positive, we get a positive voltage surge at the output of the comparator.

Another example: if the positive terminal has a voltage of +3V, and the negative input terminal has a voltage of +5V. The difference is +3-+5=-2V, since the input voltage difference is negative. The output of the comparator will be a negative peak voltage.

As an example, consider the positive input terminal as the input and the negative input terminal as the reference, as shown in the figure above. So the voltage difference between the input and the other large positive will result in a positive output of the comparator. If the difference is negative, then we will get a negative or ground at the output of the comparator.

SR multivibrator: this memory cell can store one bit of data. In the figure we see a truth table.

There are four multivibrator states for two inputs; however, we must understand that there are only two trigger states for this case.

S	R	Q	Q' (Q stroke)
0	1	0	1
1	0	1	0

Now as shown in the table, for the reset and set inputs we get the corresponding results. If there is a pulse to dial the PIN code and a low level at the reset, then the flip-flop stores the value of one and affects the high logic in the Q terminals. This state continues until reset, the PIN receives a pulse while dialing and is logic low. This will reset the flip-flop so the Q output turns off and this state continues until the flip-flop is reset.

Thus, the flip-flop stores one bit of data. Here's another thing, Q and Q-stroke are always opposite.

In a timer, a comparator and a flip-flop are combined.

Consider 9V is supplied to the Timer, due to the voltage divider formed by the resistors inside the Timer, as shown in the block diagram; there will be voltage at the contacts of the comparator. So, due to the mains voltage divider, we will have +6V on the negative terminal of the first comparator. And +3V to the positive terminal of the second comparator.

The first and other pin is one output of the comparator connected to the reset pin of the multivibrator, so if the comparator has one output going low, the flip-flop will be reset. And on the other hand, the second output of the comparator is connected to the multivibrator, so that if the second output of the comparator goes from a low value, the multivibrator stores one at a time.

With a voltage of at least +3V across the flip-flop pin (the negative input of the second comparator), the output of the comparator goes from low to high, as discussed earlier. This pulse detects the multivibrator and stores one value.

Now, if we apply a voltage higher than +6V at the threshold pin (positive input of one comparator), the output of the comparator goes from low to high. This pulse resets RS and RS stores zero.

Another thing happens during reset of the flip-flop, when it resets the discharge, the contact connected to ground under the name gets turned on Q1. Transistor T1 turns on because the Q prime is at the high reset point and is connected to the base of T1.

In an unstable configuration, the capacitance connected here will reset at this point and therefore the timer output will be low during this time. In an unstable configuration, the time during the charging of the capacitor at the trigger contact, the voltage will be less than +3V and therefore the trigger maintains one value and the output will be high.

In an unstable configuration as shown in the figure,

The frequency of the output signal depends on RA, RB resistors and capacitor C. The equation is given as,

Frequency(F) = 1/(time period) = 1.44/((RA+RB*2)*C).

Here RA, RB are the resistance values ​​and C is the capacitance value. By putting the resistance and capacitance values ​​into the above equation, we get the output square wave frequencies.

High level time logic is set as, TH= 0.693*(RA+RB)*C

Low level time logic set as, TL= 0.693*RB*C

The duty cycle of the output rectangular signal pulses is specified as, Duty factor = (RA+RB)/(RA+2*RB).

555 Timer circuit and descriptions

Contact 1. Ground: this pin must be connected to ground.

Pin 8. Power or supply voltage vcc: this pin also has no special function. It is connected to positive voltage. On the Timer, for the function to work, this pin must be connected to a positive voltage in the range of +3.6 V to +15 V.

Pin 4. Reset: as discussed earlier, there is a macro switch. The trigger output controls the microcircuit, the output is connected to pin 3 directly.

The "reset" pin is directly connected to the MR (general reset) flip-flop. When examining, we can observe a small cycle on the trigger. When the SR (general reset) pin is active the trigger level is low. This means that for the flip-flop to reset the SR pin, the voltage must go from high to low. This step down logic in the trigger occurs with difficulty going to a low level. Therefore, the output is weak, regardless of any conclusions.

This pin is connected to vcc to trigger to stop with a hard reset.

Pin 3. Output: this pin also has no special function. This contact has a push-pull configuration (PUSH-PULL) formed by transistors.

This configuration is shown in the figure. The bases of the two transistors are connected to the output of the trigger. Therefore, when a high logic level appears at the output of the flip-flop, the NPN transistor turns on and appears at the +V1 output. When the logic appearing at the output of the flip-flop goes low, the PNP transistor gets turned on and the output is connected to ground or –V1 appears at the output.

So the configuration is used to get a square wave output from the flip-flop control logic. The main purpose of this configuration is to get the trigger loaded back. But the flip-flop cannot release 100mA at the output.

Well, so far we have discussed contacts that do not change the state of the outputs in any state. The remaining four pins are special because they determine the state of the chip's timer output.

Contact 5. Control contact: the control pin is connected to the negative input pin of the first comparator.

Consider for the case the voltage between vcc and ground is 9V. Due to the voltage divider in the microcircuit, the voltage to the control pin will only be vcc*2/3 (for supply voltage vcc = 9, contact voltage = 9*2/3=6V).

This function gives the user direct control of the first comparator. As shown in the above circuit, the output of the first comparator is fed to reset the flip-flop. We can put different voltages on this pin, say if we connect it to +8V. What happens now is that the contact voltage threshold must reach +8V before the trigger is reset and pulls down to the output.

For a normal case, the minimum will go to V-Out, then the capacitor receives a charge of up to 2/3VCC (+6V for a 9V supply). Now, since we have set different voltages to the control pin (the first comparator is negative or the reset comparator).

The capacitor should be charged until the control terminal voltage is reached. The strength of the capacitor charge affects the on and off time of the signal change. Therefore, the output signal experiences various inclusions of the interval.

Usually this terminal is wound down with a capacitor. To avoid unwanted noise and interference in operation.

Pin 2. Trigger: connected to the input of the second comparator. The output of the second comparator is connected to the SET pin of the flip-flop. From the output of the second comparator we get a high voltage at the output of the timer. So we can say the trigger pin controls the output of the Timer.

Now here's what's worth observing: low voltage in the trigger forces the high voltage output to the inverting input of the second comparator. The voltage at the trigger contact must be lower than the supply voltage VCC*1/3 (with VCC 9V as expected, VCC*(1/3)=9*(1/3)=3V). Therefore, the trigger voltage must be below 3V (for a 9V supply) at the timer output to go high.

If this pin is connected to ground, the output will always be high.

Contact 6. Threshold: The voltage threshold contact determines when the trigger in the Timer is reset. The voltage threshold is designated for the positive input of comparator 1.

Here the voltage difference between the THRESOLD pin and the Control pin determines the output of comparator 2 and therefore the logic reset. If the difference voltage is positive, then the trigger is reset and the output decreases. If the difference is negative, then the logic at the SET pin determines the output.

If the control input is open. Then a voltage equal to or greater than VCC*(2/3) (ie 6V for a 9V supply) will reset the flip-flop. Therefore the output is low.

Therefore we can conclude that the voltage threshold pin determines when the output should go low if the control pin is open.

Pin 7. Reset: this pin is taken from the open collector of the transistor. Because the transistor (reset pin T1) has received a Base connection to the Q prime. Whenever the output goes low or the flip-flop gets reset, the Reset is connected to ground. When the Q prime is high, then Q will be low, so transistor T1 will receive an ON change because power has entered the base of the transistor.

This pin usually discharges the capacitor in an unstable configuration, hence the name Reset.

The 555 chip appeared forty years ago and was actually the first timer on the wide market. Since then, due to the wild popularity of the microcircuit, almost all manufacturers of electronic components began to produce it, and despite its venerable age, 555 is still produced in multi-million copies.

This year there was a competition of projects (555contest.com) using it to solve a variety of problems. Applications were accepted in several categories: art, complex projects, minimalistic and useful gadgets. The prize fund was about $1500.

Among the several hundred projects was a video game collected from a handful of 555; pinball controller; electric guitar; a device that prevents neighbors from sleeping; a lock that unlocks the door with a secret knock and a bunch of other interesting things.

If you have held a soldering iron at least once in your life and can even tell a resistor from a transistor, but you are not yet familiar with the old 555, then you urgently need to correct the situation. What kind of animal is this? Inside the plastic case with eight terminals are hidden a couple of dozen transistors, diodes and resistors, but we will not go into a thorough study of the operation of the timer; let it remain for us a black box with legs sticking out of it. But let's discuss the legs.

1. Earth. Everything is simple here; in all circuits it must be connected to the power supply minus.
2. Trigger, aka start. If the start voltage drops below one-third of the supply voltage (Vcc) - for example, a button pulled to ground is pressed - then the circuit starts.
3. Exit. The task of the timer is simple - to generate rectangular pulses of a given length (the duration is set by a pair of resistances and a capacitor). The output voltage is about 2V below the supply voltage when it is on, and almost zero (less than 0.5V) when it is off. The maximum load that the output can withstand is about 200 mA. This is enough for a small speaker, a couple of LEDs or a small relay.
4. Reset. If you apply a low level to it (less than 0.7 V), the circuit goes into its original state and the output goes low. If a reset is not needed in the circuit, then it is better to pull it to the plus so that it does not reset accidentally (for example, from touching with a finger).
5. Control. Voltage applied to this leg can change the duration of the timer outputs. But it is rarely used, and hanging in the air can disrupt operation, so in circuits it is better to connect it to ground through a small 10 nF ceramic capacitor.
6. Threshold, aka stop. If the voltage on it is higher than 2/3 Vcc, then the timer stops and the output is switched to the off state. Works only if the input is turned off.
7. Discharge. This output is connected to ground inside the chip when the output is low and is used to discharge the timing chain capacitor. Can carry up to 200 mA and is sometimes used as an additional output.
8. Nutrition. It needs to be connected to the power supply. The microcircuit supports voltages from 4.5 V to 16 V. It can be powered from a regular 9V battery, from a power supply for children's toys or from a USB cable.

Let's get a horse. Modes

1. Monostable.

When a signal is applied to the input, the microcircuit turns on, generates an output pulse of a given length, and turns off, waiting for a new input pulse. It is important that after switching on, the microcircuit will not respond to new signals, no matter how many of them are sent. The pulse length can be calculated using the simple formula t=1.1 R1 C4. To get the time in seconds, the resistance must be substituted in megaohms, and the capacitance in microfarads.

For example, with C4=100 µF and R1=2.2 MOhm, the period will be approximately 4 minutes. This figure can be changed within a very wide range: from 0.000001 seconds to 15 minutes. In theory, even more is possible, but in practice problems will arise.

2. Astable multivibrator.

In this mode, there is no need to control the timer, it is its own master - it will first turn on, wait for time t1, then turn off, wait for time t2, and all over again. The output is a fence of high and low states, which in the best tradition of ASCII art can be represented like this: P P P P P. The frequency with which the entire system will oscillate depends on the parameters of the RC chain (more precisely, on the values ​​of R2, R3 and C1) and can be calculated using the formula f = 1.44/((R3 + 2R2)C1). During the time t1 = 0.693 (R3 + R2)C1 the output will be high, and during t2=0.693(R2)C1 the output will be low.

3. Bistable.

In this mode, the chip is used as a switch. Pressed one button - the output turned on, pressed another - turned off. Enough of the theoretical excursion, you probably already want to start practicing.

It is convenient to assemble simple pieces of hardware on a breadboard without soldering - it, like all the parts, can be purchased at any radio shop for a couple of hundred rubles. But my post office is closer than the store, and I ordered all the parts from Hong Kong on sureelectronics.net, although this option is not for everyone - you need a lot of patience: the parcel will take almost a month.

Hello light!

Task #1: assemble a “Halloween World” - an LED blinker. Everything is simple, as in the world of software, but in hardware even for such a trinket you can come up with a useful use.

What details are absolutely impossible to get away from? First, the 555 timer itself (IC1 in the diagram). A timer from any manufacturer will do, but to experiment on a breadboard, take one in a DIP package with long legs. Its names vary slightly among different manufacturers, but they always have three fives. For example, the one I'm using in the examples in this article is called the NE555N. There are other versions of the circuit, 556 and 558, which have 2 and 4 timers in one case, respectively.

They are also suitable for all examples, they just have more legs and they are positioned differently. Secondly, you will need capacitors: electrolytic C1 with a capacity of 5 to 10 μF and ceramic C3 with a capacity of 10 nF. You will also need: an LED (LED1) of any color and a current-limiting resistor (R5) of 300-600 Ohms (I have 470 Ohms), as well as resistors that set the frequency R1 by 1 kOhm and R2 by 10 kOhm. The last of the mandatory programs is a small button (like the one they put in mice and on all kinds of dashboards).

There is also a 100 µF capacitor C2 in the diagram, which is transferred from plus to minus. If everything is fine with your power supply (for example, you use a battery), then there is no need for it, but with a cheap network adapter you can’t go without such a capacitor. In the examples, I used a five-volt power supply from a Chinese children's toy, the manufacturer of which saved on the rectifier - as a result, without this smoothing capacitance, the circuit did not work at all. Therefore, all the diagrams in the article have this capacitor, but it’s up to you to decide whether to install it or not.

Also, if desired, you can lower capacitor C3, which attracts the fifth leg to the ground, but in this case I will not guarantee stability.
The circuit operates in an unstable mode and is assembled in such a way that while it is connected to power, it constantly generates output pulses, and as soon as we press the button, we close its output to the LED and its operation becomes visible. Now you can assemble everything according to the diagram.

When you press the button, the LED should start blinking vigorously. If it doesn't work, check the contacts and polarities. On the 555 chip there is a notch at one of the edges: place the circuit so that the notch is on the left, then the legs in the bottom row will be numbered from left to right from 1 to 4, and in the top - from right to left from 5 to 8. The LED should have a longer output connect to the plus, and the shorter one to the minus. If the diode's legs are the same length, then a flat lithium battery, like the one found on motherboards, will come to the rescue. Connect the LED this way and that, when it lights up, its plus and minus will be located like on a battery.

If it does not work in both positions, then either the diode is burnt out or it is not a diode - phototransistors can look exactly the same as LEDs. For electrolytic capacitors, the minus is usually marked with a light stripe on the body. For other parts, polarity is not important.

Now about the practical benefits. In some games, it may be necessary to click the left button incessantly, rubbing calluses on your finger, but this is not our method. You can assemble this circuit more compactly by soldering the parts directly to the outputs of the microcircuit, and stuff it into the body of any USB mouse - there is usually enough space there. You just need to remove the LED with its resistor from the circuit, and solder the third leg of the microcircuit directly to the plus of the left mouse button.

Determining where in the mouse button is a plus (green dot in the photo) and where is a minus is usually not difficult: the contact with zero is thicker and goes to the black wire from the USB, and the other is a plus, solder to it. For power, connect to the red and black wires going towards the computer, their contacts are also marked in the photo. We drilled a hole on the left side of the mouse body (so that it would be convenient to reach it with your thumb) and install the button there using a hot glue gun. That's it, now you can mercilessly cut down your enemies.

We create electronic music

Another circuit in which the timer also operates in multivibrator mode, but its task is different. It will take you back in time, to the smoky studios of the fathers of underground electronic music, who themselves had to sculpt the devices with which they created immortal hits.

Changes to the previous scheme will have to be made very small. Instead of an LED with its resistor, there is a speaker connected to ground through capacitor C4 - it is needed to filter the DC component of the output and drive only alternating current through the speaker. For maximum volume, this capacitor should be electrolytic, with a capacity of about 10 uF, but such a sound will hurt the ear, and if such a task is not worth it, put a ceramic one at 100 nF, it will be quieter. You can take a speaker from broken large headphones or a beeper from an old system unit. A piezo speaker (in the form of a round metal plate) is also suitable, plus it does not need capacitor C4.

Since the sound frequencies are slightly higher than the blinking frequency of the diode, the RC circuit will also have to be slightly altered. Replace capacitor C1 with a 100 nF ceramic one, replace resistor R2 with 1 kOhm and place a 10 kOhm variable resistor R3 in series with it. Variable resistors usually have 3 legs arranged in a row, but you only need to connect two - any of the outer ones and the central one. Such parameters will not allow the frequency to escape beyond the audible range throughout the entire R3 range. Use a resistor to set the frequency, press the button and listen to what it sounds. With some skill you will get music.

Servo as a finger extension

Another circuit in multivibrator mode. Here, using the 555 timer, you will control the servo. Turn the variable resistor, and the machine will turn whatever you want. Servo drives (or simply servos) are usually used in radio-controlled model cars/helicopters/planes, but this does not mean that you will not find other uses for them.

First, you need to get this machine somewhere. There is a good selection of inexpensive servers in the popular Chinese online store DealExtreme (s.dealextreme.com/search/servo), I ordered all of mine there. We also have them in our stores, but noticeably more expensive.

A typical hobby servo has three wires: black or brown negative power, which should be connected to the SERVO-3 pin on the diagram, red positive - to SERVO-1, yellow or white for control commands - to SERVO-2.

The servo expects that short pulses with a length of 0.9 to 2.1 ms will arrive along the signal wire 50 times per second, and the duration of the signal will tell you at what angle to deviate. The parameters of the RC chain in the circuit are selected in such a way as to provide just such signals. Since the pulse time must be less than the time between them, diode D1 must be added to the circuit. The diagram shows 1n4148, since it is one of the most common, but you can replace it with another. It is easy to determine the polarity of the diode - the perpendicular strip on the body corresponds to the line on the diagram.

The 555 timer is a simple thing, even if you supply 15 volts to the input, it doesn’t care. But the servo requires more careful handling and only works in the voltage range from 4.8 V to 6 V. So if you used a 9 V battery for power, you will have to lower the voltage. The 7805 stabilizer copes with this task perfectly, cutting off all excess and leaving clean 5 V at the output. However, it simply converts all the extra volts into heat and can get very hot. Although, when heated, the stabilizer maintains a pleasant warm microclimate in the room, it should not be used in projects powered by batteries - it is voracious. It’s easy to include it in the circuit: if you take it by the outputs and read the inscriptions on the case, then the first leg will be on the left - it needs to be connected to the battery positive, the second to the common ground, and the third to the +5 V output.

By assembling this thing, you can not only test the servos for functionality, but also remotely control switches and open locks.

Permanent button

Sometimes you need your circuit to work like a TV: press a button, it turns on, press it again, it turns off. And this problem can also be solved on the 555. A trigger is hidden inside the chip, which can be used for this purpose.

The main part of the circuit should no longer raise any special questions for you; I will only focus on the output of the third leg, namely resistor R4 and transistor T1. After all, we are making a button, which means it must be able to pass current, and it is not a fact that 200 mA, which the 555 is capable of, will be enough. Here, a small NPN transistor 2N3904 is used as a key, which is capable of passing the same 200 mA as the timer itself, and there is little point in it, but it can always be replaced with a more powerful MOS transistor - for example, IRF630, which will allow you to connect the load up to 9A. True, for such a trance the voltage on the circuit will have to be increased to 12 volts, otherwise the shutter will not open.

It’s still not very cool to use such a switch in mobile devices, since even when turned off it consumes a current of 3-6 mA, which significantly drains the battery.

Tea making gadget

When I first started getting acquainted with Linux, I came across a small but very important program for making tea. In it you can select the type of tea, and after the time required for brewing, it began to blink with an icon in the tray and beep. I don’t remember what distribution the program was from, but it helped me drink hot tea a couple of times. It’s always like this with programs: you demolished the operating system and it’s gone, but the hardware on the table is much more reliable!

To implement this contraption, you will need as many as two 555 timers. One (the one in the diagram on the left) will count down 4 minutes, during which the brew turns into a fragrant drink, and the other will generate impulses for the beeper.

The generator on IC2 diligently and continuously generates pulses. Let's take a closer look at the first timer. It is connected in monostable mode. In the normal state, immediately after turning on the power, output 3 has a low level - it is pulled to the ground, which means the speaker beeps and LED2 lights up (in fact, the LED blinks, but very quickly, and this is imperceptible). As soon as the S1 button is pressed, the timer turns on, output 3 becomes high, LED1 lights up, and the speaker turns off, because LED2, although a “light”, is still a diode, and will not pass current in the opposite direction. This continues while capacitor C4 is charged through resistor R1. When the voltage on pin 6 becomes more than 2/3 Vcc, the timer will turn off and the beeper will beep again.

The circuit can be slightly modified by adding R1 in series - a 500 kOhm variable resistor, then it will be possible to adjust the brewing time for different types of tea.

I'm sure these diagrams will be enough inspiration for you. If not, try looking for something on instructables.com. Also, the program 555 Timer Pro can help with diagrams schematica.com/555_Timer_design/555_Timer_PRO_EX.htm, which allows you to calculate the details for any mode in a couple of clicks (however, it costs “only” $29, but if you try, you can find an older one on the Internet free version).

555 microcircuits are used quite often in amateur radio practice - they are practical, multifunctional and very easy to use. On such microcircuits, you can implement any design - both the simplest Schmitt triggers with a couple of additional elements, and multi-stage combination locks.

The NE555 was developed quite a long time ago, even in the Soviet magazines “Radio” and “Modelist-Konstruktor”; many homemade products could be found using analogues of this microcircuit. Today, this chip is actively used in designs with LEDs.

Description of the chip

This is the development of a company from the USA Signetics. It was its specialists who were able to put into practice the work of Camenzind Hans. This, one might say, is the father of the integrated circuit - in difficult conditions of high competition, engineers managed to make a product that entered the world market and gained wide popularity.

In those years, the 555 series microcircuit had no analogues in the world - a very high density of elements in the device and extremely low cost. It is thanks to these parameters that it has earned high popularity among designers.

Domestic analogues

Afterwards, mass copying of this radio element began - the Soviet analogue of the microcircuit was called KR1006VI1. By the way, it is a unique development in all respects, even though it has many analogues. Only in domestic microcircuits the stop input has priority over the start input. None of the foreign designs have such a feature. But this feature must be taken into account when designing circuits in which both inputs are actively used.

Where is it used?

But it should be noted that input priorities do not greatly affect the performance of the microcircuit. This is only a minor nuance that needs to be taken into account in rare cases. To reduce power consumption, the production of CMOS elements was launched in the mid-70s. In the USSR, microcircuits on field workers were called KR1441VI1.

Generators based on the 555 chip are very often used in amateur radio designs. It is not difficult to implement a time relay on this chip, and the delay can be set from a few milliseconds to hours. There are also more complex elements, which are based on a 555 circuit - they contain devices to prevent contact rattling, PWM controllers, and digital signal restoration.

Advantages and disadvantages of the microcircuit

There is a built-in voltage divider inside the timer - it is this that allows you to set a strictly fixed lower and upper threshold at which the comparators operate. It is from here that we can draw a conclusion about the main drawback - it is impossible to control the threshold values, and it is also impossible to exclude the divider from the design; the scope of practical application of the 555 microcircuit is significantly narrowed. It is possible to build multivibrator and monovibrator circuits, but more complex designs will not work.

How to get rid of shortcomings?

But you can get rid of this problem by simply installing a polar capacitor of no more than 0.1 μF between the control terminal and the power supply minus.

And in order to significantly increase noise immunity, a non-polar capacitor with a capacity of 1 µF is installed in the power circuit. When using 555 microcircuits in practice, it is important to consider whether passive elements - resistors and capacitors - affect their operation. But you need to note one feature - when using timers on CMOS elements, all these disadvantages simply go away; there is no need to use additional capacitors.

Basic parameters of microcircuits

If you decide to make a timer on a 555 chip, then you need to know its main features. There are a total of five nodes in the device; they can be seen in the diagram. At the input there is a resistive voltage divider. With its help, two reference voltages are formed, which are necessary for the operation of the comparators. The outputs of the comparators are connected to an RS flip-flop and an external reset pin. And only after that to the amplification device, where the signal value increases.

Power supply for microcircuits

At the end there is a transistor whose collector is open - it performs a number of functions, everything depends on what specific task is facing it. It is recommended to supply NE, SA, NA integrated circuits with a supply voltage in the range of 4.5-16 V. Only when using 555 microcircuits with the abbreviation SE is an increase to 18 V allowed.

The maximum current consumption at a voltage of 4.5 V can reach 10-15 mA, the minimum value is 2-5 mA. There are CMOS microcircuits whose current consumption does not exceed 1 mA. For domestic ICs of the KR1006VI1 type, the current consumption does not exceed 100 mA. A detailed description of the 555 chip and its domestic analogues can be found in the datasheets.

Operation of the chip

Operating conditions depend directly on which company produces the microcircuit. As an example, we can cite two analogues - NE555 and SE555. For the first, the temperature range in which it will normally operate is in the range of 0-70 degrees. In the second it is much wider - from -55 to +125 degrees. Therefore, such parameters must always be taken into account when designing devices. It is advisable to familiarize yourself with all typical voltage and current values ​​​​at the Reset, TRIG, THRES, CONT pins. To do this, you can use the datasheet for a specific model - you will find comprehensive information in it.

The practical application of the scheme also depends on this. The 555 chip is used quite often by radio amateurs - in control systems there are even master oscillators for radio transmitters based on this element. Its advantage over any transistor or tube version is its incredibly high frequency stability. And there is no need to select elements with high stability or install additional devices for voltage equalization. It is enough to install a simple microcircuit and amplify the signal that will be generated at the output.

Purpose of IC pins

The 555 series microcircuits have only eight pins, package type PDIP8, SOIC, TSSOP. But in all cases the purpose of the conclusions is the same. The element UGO is a rectangle labeled “G1” in the case of a single pulse generator and “GN” for a multivibrator. Pin assignment:

1. GND is general, it is the first in order (if you count from the tag key). This pin is supplied with minus from the power source.
2. TRIG - trigger input. It is to this pin that a low-level pulse is applied and it goes to the second comparator. As a result, the IC starts up and a high level signal appears at the output. Moreover, the duration of the signal depends on the values ​​of C and R.
3. OUT is the output at which the high and low level signal appears. Switching between them takes no more than 0.1 μs.
4. RESET - reset. This input has the highest priority; it controls the timer, and this does not depend on whether there is voltage on the other legs of the microcircuit. To allow startup, a voltage above 0.7V must be present. If the pulse is less than 0.7V, then the operation of the 555 chip is prohibited.
5. CTRL is a control input that is connected to a voltage divider. And if there are no external factors that can affect the operation, a voltage of 2/3 of the supply voltage is output at this output. When a control signal is applied to this input, a modulated pulse is generated at the output. In the case of simple circuits, this output is connected to a capacitor.
6. THR - stop. This is the input of the 1st comparator; if a voltage of 2/3 of the supply voltage appears on it, the trigger operation stops and the timer is set to a lower level. But a prerequisite is that there should not be a trigger signal on the TRIG leg (since it has priority).
7. DIS - discharge. It connects directly to the transistor located inside the 555 chip. It has a common collector. A capacitor is installed in the emitter-collector circuit, which is necessary to set the time.
8. VCC - connection to the positive of the power supply.

One-shot mode

In total, there are three operating modes of the NE555 chip, one of them is a monostable. To generate pulses, you have to use a polar-type capacitor and a resistor.

The circuit works like this:

1. A voltage is applied to the timer input - a low-level pulse.
2. The operating mode of the microcircuit is switched.
3. A high level signal appears at pin “3”.

After this time, a low-level signal will be generated at the output. In multivibrator mode, pins “4” and “8” are connected. When developing circuits based on a one-shot device, you need to take into account the following nuances:

1. The supply voltage cannot influence the pulse time. As the voltage increases, the charging rate of the capacitor, which sets the time, is greater. Consequently, the amplitude of the output signal increases.
2. If you apply an additional pulse to the input (after the main one), it will not affect the operation of the timer until the end of time t.

To influence the operation of the generator, you can use one of the following methods:

1. Apply a low-level signal to the RESET pin. This will return the timer to its default state.
2. If a low-level signal goes to input “2,” then the output will always have a high pulse.

By using single pulses applied to the input and changing the parameters of the timing components, it is possible to obtain a rectangular signal of the required duration at the output.

Multivibrator circuit

Any novice radio amateur can make a metal detector using a 555 chip, but to do this, you need to study the operating features of this device. A multivibrator is a special generator that produces rectangular pulses at a certain periodicity. Moreover, the amplitude, duration and frequency are strictly specified - the values ​​​​depend on what task the device is facing.

Resistors and capacitors are used to generate repeating signals. The signal duration t1, pause t2, frequency f, and period T can be found using the following formulas:

• t1=ln2*(R1+R2)*C=0.693*(R1+R2)*C;
• t2=0.693*C*(R1+2*R2);
• T=0.693*C*(R1+2*R2);
• f=1/(0.693*C*(R1+2*R2)).

Based on these expressions, it can be seen that the duration of the pause should not be longer than the signal time. In other words, the duty cycle will never be greater than 2. The practical application of the 555 microcircuit directly depends on this. Circuits of various devices and designs are built according to datasheets - instructions. They give all possible recommendations for assembling devices. The duty cycle can be found using the formula S=T/t1. To increase this figure, it is necessary to add a semiconductor diode to the circuit. Its cathode is connected to the sixth leg, and the anode to the seventh.

If you look at the datasheet, it indicates the inverse value of the duty cycle - it can be calculated using the formula D=1/S. It is measured as a percentage. The operation of a multivibrator circuit can be described as follows:

1. When power is applied, the capacitor is completely discharged.
2. The timer is placed in a high-level state.
3. The capacitor accumulates charge and the voltage across it reaches a maximum - 2/3 of the supply voltage.
4. The microcircuit switches and a low-level signal appears at the output.
5. The capacitor is discharged during t1 to a level of 1/3 of the supply voltage.
6. The 555 chip switches again and the output again produces a high-level signal.

This mode of operation is called self-oscillating. The signal value at the output is constantly changing; the 555 timer microcircuit is in different modes for equal periods of time.

Precision Schmitt trigger

Timers like NE555 and similar ones have a built-in comparator with two thresholds - lower and upper. In addition, it has a special RS trigger. This is what makes it possible to implement the design of a precision Schmitt trigger. The voltage supplied to the input is divided into three equal parts using a comparator. And as soon as the threshold value level reaches, the operating mode of the microcircuit switches. In this case, the hysteresis increases, its value reaches 1/3 of the supply voltage. A precision trigger is used in the design of automatic control systems.