555 chips are used quite often in amateur radio practice - they are practical, multifunctional and very easy to use. Any design can be implemented on such microcircuits - both the simplest Schmitt triggers with a couple of additional elements, and multi-stage combination locks.
NE555 was developed quite a long time ago, even in the Soviet magazines "Radio", "Modelist-Constructor", on the analogs of this microcircuit one could find many homemade products. Today this microcircuit is actively used in designs with LEDs.
Chip Description
This is the development of the US company 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 an integrated microcircuit - 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 assembly of elements in the device and an extremely low cost price. It is thanks to these parameters that it has earned high popularity among designers.
Domestic analogues
After that, the massive copying of this radio element began - the Soviet analogue of the microcircuit was called KR1006VI1. By the way, it is in every respect a unique development, even though it has many analogues. Only in domestic microcircuits the stop input has a higher priority than the start input. None of the foreign designs has such a feature. But this feature must be taken into account when designing circuits in which both inputs are actively used.
Where is it applied?
But it should be noted that the priorities of the inputs do not greatly affect the performance of the microcircuit. This is just a small nuance that should 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 on the 555 chip are very often used in the designs of radio amateurs. It is not difficult to implement a time relay on this microcircuit, and the delay can be set from a few milliseconds to hours. There are also more complex elements, which are based on the 555 circuit - they contain devices for preventing contact rattling, PWM controllers, restoring a digital type signal.
Advantages and disadvantages of the microcircuit
There is a built-in voltage divider inside the timer - it is he who allows you to set a strictly fixed lower and upper threshold at which the comparators are triggered. It is from this that we can draw a conclusion about the main drawback - the threshold values \u200b\u200bcannot be controlled, and the divider cannot be excluded from the design, the area of \u200b\u200bpractical application of the 555 microcircuit is significantly narrowed. Multivibrator and one-shot circuits can be built, but more complex designs will not work.
How to get rid of the flaws?
But you can get rid of such a problem, it is enough to install a polar capacitor of no more than 0.1 μF between the control output and the power supply minus.
And in order to significantly increase the noise immunity, a non-polar capacitor with a capacity of 1 μF is installed in the power circuit. In the practical application of 555 microcircuits, it is important to consider whether passive elements - resistors and capacitors - affect their operation. But one feature should be noted - when using timers on CMOS elements, all these disadvantages simply go away, there is no need to use additional capacitors.
Main parameters of microcircuits
If you decide to make a timer on a 555 chip, then you need to know its main features. In total, the device has five nodes, they can be seen in the diagram. A resistive voltage divider is located at the input. With its help, two reference voltages are formed, which are necessary for the operation of the comparators. Comparator outputs are connected to an RS flip-flop and an external reset pin. And only after that to the amplifying device, where the signal value increases.
Power supply of microcircuits
At the end there is a transistor with an open collector - it performs a number of functions, everything depends on what specific task it faces. It is recommended to supply voltage in the range of 4.5-16 V to the NE, SA, NA integrated circuits.
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 in which the 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 counterparts can be found in the datasheet.
Operation of the microcircuit
The operating conditions depend directly on which company produces the microcircuit. As an example, there are two analogs - NE555 and SE555. In the first, the temperature range in which it will normally work 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 the typical values \u200b\u200bof voltages and currents at the Reset, TRIG, THRES, CONT pins. To do this, you can use a datasheet for a specific model - in it you will find comprehensive information.
The practical application of the scheme depends on this. Radio amateurs use the 555 chip quite often - in control systems there are even master oscillators for radio transmitters 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, to 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.
IC pin assignment
On the 555 series microcircuits there are only eight pins, the type of package is PDIP8, SOIC, TSSOP. But in all cases, the purpose of the conclusions is the same. The UGO element is a rectangle labeled "G1" in the case of a single pulse generator and "GN" for a multivibrator. Pin assignment:
- GND - common, in order it is the first (if you count from the key-tag). This pin is supplied with a minus from the power supply.
- TRIG - trigger input. It is to this pin that a low-level pulse is fed 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 signal duration depends on the values \u200b\u200bof C and R.
- OUT - the output at which the high and low level signals appear. Switching between them takes no more than 0.1 μs.
- RESET - reset. This input has the highest priority, it controls the timer, and it does not depend on whether there is voltage on the other legs of the microcircuit. To allow starting, a voltage of over 0.7V is required. In the event that the pulse is less than 0.7V, then the operation of the 555 microcircuit is prohibited.
- CTRL is a control input that connects to a voltage divider. And if there are no external factors that can affect the operation, 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.
- 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 stops and the timer is transferred to a low level. But a prerequisite is that there should be no trigger signal on the TRIG leg (since it has priority).
- DIS - discharge. It connects directly to a transistor inside the 555 chip. It has a common collector. A capacitor is installed in the emitter-collector circuit, which is necessary in order to set the time.
- VCC - connection to the plus of the power supply.
Single shot mode
In total, there are three modes of the NE555 microcircuit, one of them is a one-shot. To implement the pulse shaping, it is necessary to use a polar-type capacitor and a resistor.
The circuit works like this:
- Voltage is applied to the timer input - a low-level pulse.
- The operating mode of the microcircuit is switched.
- A high signal appears at pin 3.
After this time, a low-level signal will be formed at the output. In the multivibrator mode, pins "4" and "8" are connected. When developing circuits based on a single shot, you need to take into account the following nuances:
- The supply voltage cannot influence the pulse time. With increasing voltage, the charging rate of the capacitor, which sets the time, is faster. Consequently, the output signal amplitude increases.
- If an additional pulse is applied to the input (after the main one), it will not affect the timer's performance until the end of time t.
To influence the functioning of the generator, you can use one of the following methods:
- Apply a low-level signal to the RESET pin. This will return the timer to its default state.
- If a low-level signal goes to input "2", then the output will always have a high pulse.
With the help of single pulses applied to the input, and changing the parameters of the timing components, it is possible to obtain a square-wave signal of the required duration at the output.
Multivibrator circuit
Any novice radio amateur can make a metal detector on a 555 microcircuit, but for this you need to study the features of the operation of this device. A multivibrator is a special generator that produces rectangular pulses at a certain frequency. Moreover, the amplitude, duration and frequency are strictly set - the values \u200b\u200bdepend on the task facing the device.
Resistors and capacitors are used to generate repetitive signals. The signal duration t1, pauses t2, frequency f, and period T can be found using the following formulas:
- t1 \u003d ln2 * (R1 + R2) * C \u003d 0.693 * (R1 + R2) * C;
- t2 \u003d 0.693 * C * (R1 + 2 * R2);
- T \u003d 0.693 * C * (R1 + 2 * R2);
- f \u003d 1 / (0.693 * C * (R1 + 2 * R2)).
Based on these expressions, you can see that the pause duration 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 structures are built according to datasheets - instructions. They provide all possible recommendations for assembling devices. The duty cycle can be found by the formula S \u003d T / t1. To increase this figure, it is necessary to add a semiconductor diode to the circuit. Its cathode connects to the sixth leg, and the anode to the seventh.
If you look at the datasheet, then the reciprocal of the duty cycle is indicated in it - it can be calculated using the formula D \u003d 1 / S. It is measured as a percentage. The operation of the multivibrator circuit can be described as follows:
- The capacitor is completely discharged when power is applied.
- The timer is put into a high-level state.
- The capacitor accumulates a charge and the voltage across it reaches a maximum - 2/3 of the supply voltage.
- The microcircuit switches and a low-level signal appears at the output.
- The capacitor is discharged during t1 to the level of 1/3 of the supply voltage.
- The 555 chip switches again and a high-level signal is generated at the output again.
This mode of operation is called self-oscillating. The signal value is constantly changing at the output, the 555 timer chip is in different modes for equal periods of time.
Precision Schmitt Trigger
Timers such as NE555 and similar 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 applied to the input is divided by a comparator into three equal parts. And as soon as the level of the threshold value is reached, the operating mode of the microcircuit is switched. In this case, the hysteresis increases, its value reaches 1/3 of the supply voltage. A precision trigger is used in the design of systems with automatic control.
The modern market for electronic components and various devices based on them is mainly filled with Chinese manufacturers. Most of both the simplest Christmas tree lights, thermostats, photo relays, and complex household appliances (computers, TVs) are made in China. Also, shipping from the same is free in most cases, so many radio amateurs have already switched to electronic components from China. However, interest in simple designs has not yet disappeared.
The simplest electronic circuits still find their way into home automation systems. Many of them include the NE555 integrated timer chip or its domestic analogue KR1006VI1. Based on the NE555 timer, photo relay circuits, alarm systems, voltage converters and many others are built.
1 Photo relay based on integral timer NE555
The circuit of a photo relay based on the NE555 timer is shown in Figure 1.
Picture 1
The algorithm of the circuit is as follows: changing the illumination causes the LS1 lamp to turn on or off. The presented circuit can be divided into three functional blocks: a power supply unit, a load switching unit and an illumination measurement unit.
Power Supply in the above diagram, it has no galvanic isolation of the supply network and control circuit. Adjustment of the illumination level at which the light bulb switches is performed once, therefore constant access to the circuit elements is not required and, accordingly, no additional measures are required to ensure protection against electric shock. It is recommended to set up with an external power supply unit connected with an output voltage of 12V. The operation of the circuit can be observed on the LED1 LED.
The photo relay power supply consists of a diode rectifier Br1 (1N4407), a quenching capacitor C2, a filter capacitor C14, a Zener diode D1 (1N4467 or 1N5022A) and a smoothing resistor R5.
Load switching unit is built on the basis of the KR1182PM1A microcircuit, which generates control signals for the T1 triac (KU208G or BT139 - 600). The control signals of the microcircuit are fed to terminals 5 and 6. When contacts 5 and 6 are closed (the transistor of the AOT128 optocoupler is closed), the lamp is disconnected from the network. A capacitor C13 is used to adjust the brightness of the lamp.
Light meter photo relay is being built on the basis of NE555. A photoresistor LDR1 and a trimmer resistor R7 are connected to the input of the timer microcircuit (setting the relay threshold). Switching of output signals is provided by the NE555 timer. The operation algorithm of the light meter is as follows: the output signals of the timer are determined by the voltage across the resistor R7. At a low voltage level on R7 (the photosensor did not work and its resistance is high), a high signal level is set at the output of timer 3, the optocoupler is extinguished and the transistor is closed, and the light is on. When the resistance of the photosensor decreases, the voltage on R7 rises to the threshold value 2 / 3Upit, resulting in a low voltage level at the timer output. The load switching circuit can be replaced with a simple relay (Figure 2).
Picture 2
To connect the load (light bulb) with a certain time interval relative to the power-on of the device, use the circuit shown in Figure 3 or Figure 4. The figures also show timing diagrams of the operation of the circuits (the dashed line shows the supply voltages, the solid line shows the output voltages)
Figure 3
Figure 4
2 Alarm devices based on the NE555 integrated timer chip
2.1 Liquid level switch (picture 5)
Figure 5
The circuit of the liquid level indicator based on the NE555 integral timer is a self-oscillating multivibrator.
The principle of operation of the circuit is as follows: two electrodes are immersed in a container with water. With a sufficient liquid level, both electrodes are immersed in water and the resistance between them is small (capacitor C1 is closed). In this case, the input signals of the timer (pins 2 and 6) are equal to zero, and the output signal (pin 3) is set to a high voltage level and the generator does not work.
A decrease in the liquid level will lead to the fact that the electrodes are in the air, and therefore the resistance between them will increase. As a result, the capacitor C1 will be connected to the input signals of the microcircuit and the generator will begin to generate pulses. The frequency of the generated pulses is determined by the parameters of the RC circuit.
2.2 Alarm circuit based on the NE555 integral timer (picture 6)
Figure 6
The timer is started when the S2 limit switch is closed. Resetting to the initial state is carried out by contact S1.
The history of the creation of a very popular microcircuit and a description of its internal structure
One of the legends of electronics is integrated timer chip NE555... It was developed back in 1972. Not every microcircuit and not even every transistor can be proud of such longevity. So what is so special about this microcircuit, which has three fives in its marking?
Serial production of the NE555 chip began by Signetics exactly one year after it was developed by Hans R. Camenzind... The most surprising thing in this story was that at that time Kamenzind was practically unemployed: he quit PR Mallory, but did not have time to get a job. In fact, it was a "home preparation".
The microcircuit saw the light of day and gained such great fame and popularity thanks to the efforts of the manager of Signetics, Art Fury, who, of course, was a friend of Camenzind. Previously, he worked at General Electric, so he knew the electronics market, what is required there, and how to attract the attention of a potential buyer.
According to the memoirs of Camenzind A. Fury was a real enthusiast and lover of his craft. At home he had a whole laboratory filled with radio components, where he conducted various research and experiments. This made it possible to accumulate vast practical experience and deepen theoretical knowledge.
At that time, the products of Signetics were referred to as "5 **", and the experienced A. Fury, who had an uncanny sense of the electronics market, decided that the 555 marking (three fives) would be very useful for the new microcircuit. And he was not mistaken: the microcircuit went just like hot cakes, it became, perhaps, the most massive in the history of the creation of microcircuits. The most interesting thing is that the microcircuit has not lost its relevance to this day.
A little later, two letters appeared in the marking of the microcircuit, it became known as NE555. But since in those days there was complete confusion in the patenting system, everyone rushed to release the integral timer, naturally, putting other (read your) letters in front of the three fives. Later, on the basis of the 555 timer, dual (IN556N) and quad (IN558N) timers were developed, naturally, in more multi-pin packages. But the same NE555 was taken as a basis.
Figure: 1. Integral timer NE555
555 in the USSR
The first description of 555 in the domestic radio engineering literature appeared already in 1975 in the journal "Electronics". The authors of the article noted the fact that this microcircuit will enjoy no less popularity than the operational amplifiers that were already widely known at that time. And they were not in the least mistaken. The microcircuit made it possible to create very simple designs, and, moreover, almost all of them began to work immediately, without painful adjustment. But it is known that the repeatability of a design at home increases in proportion to the square of its "simplicity".
In the Soviet Union at the end of the 80s, a complete analogue of 555 was developed, which received the name KR1006VI1... The first industrial application of the domestic analogue was in the Electronica VM12 video recorder.
The internal structure of the NE555 chip
Before we grab the soldering iron and start assembling the structure on an integral timer, let's first figure out what's inside and how it all works. After that, it will be much easier to understand how a particular practical scheme works.
There are over twenty inside the integral timer, the connection of which is shown in the figure -
As you can see, the schematic diagram is rather complicated and is presented here for general information only. After all, all the same, you can't fit into it with a soldering iron, it will not be possible to repair it. Strictly speaking, this is how all other microcircuits, both digital and analog, look from the inside (see -). This is the technology for the production of integrated circuits. It will also not be possible to understand the logic of the device as a whole using this scheme, therefore, a functional diagram is shown below and its description is given.
Technical data
But, before dealing with the logic of the microcircuit, you should probably give its electrical parameters. The supply voltage range is wide enough 4.5 ... 18V, and the output current can reach 200mA, which allows using even low-power relays as a load. The microcircuit itself consumes very little: only 3 ... 6mA is added to the load current. At the same time, the accuracy of the timer itself practically does not depend on the supply voltage - only 1 percent of the calculated value. The drift is only 0.1% / volt. The temperature drift is also small - only 0, 005% / ° C. As you can see, everything is fairly stable.
Functional diagram NE555 (KR1006VI1)
As mentioned above, in the USSR they made an analogue of the bourgeois NE555 and named it KR1006VI1. The analog turned out to be very successful, no worse than the original, so you can use it without any fears or doubts. Figure 3 shows a functional diagram of the integrated timer KR1006VI1. It also fully corresponds to the NE555 chip.
Figure 3. Functional diagram of the integrated timer KR1006VI1
The microcircuit itself is not that big - it is produced in an eight-pin DIP8 package, as well as in a small-sized SOIC8. The latter suggests that the 555 can be used for SMD - mounting, in other words, the developers are still interested in it.
There are also few elements inside the microcircuit. The main one is DD1. When a logical unit is applied to the R input, the flip-flop is reset to zero, and when a logical unit is applied to the S input, it is naturally set to one. For the formation of control signals at the RS - inputs, it is used, which will be discussed a little later.
The physical levels of a logical unit depend, of course, on the used supply voltage and practically range from Upit / 2 almost to full Upit. Approximately the same ratio is observed for logic microcircuits of the CMOS structure. The logical zero is, as usual, in the range of 0 ... 0.4V. But these levels are inside the microcircuit, one can only guess about them, but you cannot touch them with your hands, you cannot see them with your eyes.
Output stage
To increase the load capacity of the microcircuit, a powerful output stage on transistors VT1, VT2 is connected to the trigger output.
If the RS - flip-flop is reset, then the output (pin 3) is a logic zero voltage, i.e. open transistor VT2. In the case when the flip-flop is set at the output, it is also a logic-one level.
The output stage is made according to a push-pull scheme, which allows you to connect the load between the output and the common wire (pins 3,1) or the power bus (pins 3,8).
A quick note on the output stage. When repairing and setting up devices on digital microcircuits, one of the methods for checking the circuit is to apply a low level signal to the inputs and outputs of microcircuits. As a rule, this is done by shorting these very inputs and outputs to the common wire using a sewing needle, while not causing any harm to the microcircuits.
In some circuits, the NE555's power supply is 5V, so it seems that this is also digital logic and can also be dealt with quite freely. But actually it is not. In the case of the 555 microcircuit, or rather with its push-pull output, such "experiments" cannot be done: if the output transistor VT1 at this moment is in the open state, then a short circuit will result and the transistor will simply burn out. And if the supply voltage is close to maximum, then a deplorable ending is simply inevitable.
Additional transistor (pin 7)
In addition to the mentioned transistors, there is also a VT3 transistor. The collector of this transistor is connected to the output of the microcircuit 7 "Discharge". Its purpose is to discharge the timing capacitor when using the microcircuit as a pulse generator. The discharge of the capacitor occurs at the time of reset of the trigger DD1. If you recall the description of the trigger, then at the inverse output (indicated in the diagram with a circle) at this moment there is a logical unit, leading to the opening of the transistor VT3.
Reset signal (pin 4)
The trigger can be reset at any time - the "reset" signal has a high priority. For this, there is a special input R (pin 4), designated in the figure as Usbr. As can be understood from the figure, the reset will occur if a low-level pulse is applied to pin 4, no more than 0.7V. In this case, a low level voltage will appear at the output of the microcircuit (pin 3).
In cases where this input is not used, a logic-one level is applied to it to get rid of impulse noise. The easiest way to do this is by connecting pin 4 directly to the power rail. In no case should you leave it, as they say, in the "air". Then you will have to wonder and ponder for a long time, why does the circuit work so unstable?
General Trigger Notes
In order not to get confused at all in what state the trigger is, it should be recalled that when reasoning about a trigger, the state of its direct output is always taken into account. Well, if it is said that the trigger is "set", then on the direct output the state of a logical unit. If they say that the flip-flop is "reset", then the state of logic zero is sure to be at the direct output.
At the inverse output (marked with a small circle), everything will be exactly the opposite, therefore, often the trigger output is called paraphase. In order not to confuse everything again, we will not talk about this anymore.
Anyone who has carefully read up to this point, may ask: “Excuse me, this is just a trigger with a powerful transistor stage at the output. And where is the actual timer itself? " And he will be right, since business has not yet reached the timer. To get the timer, his father, the creator, Hans R. Camenzind, invented an original way to control this trigger. The whole trick of this method lies in the formation of control signals.
Formation of signals at RS - trigger inputs
So what did we do? Everything inside the timer is fueled by the DD1 trigger: if it is set to one, there is a high level voltage at the output of the microcircuit, and if it is reset, then at pin 3 a low level and, in addition, the VT3 transistor is open. The purpose of this transistor is to discharge a timing capacitor in a circuit, for example, a pulse generator.
The DD1 trigger is controlled using the comparators DA1 and DA2. In order to control the operation of the trigger at the outputs of the comparators, you need to receive high-level R and S signals. A reference voltage is supplied to one of the inputs of each comparator, which is formed by a precision divider across resistors R1 ... R3. The resistance of the resistors is the same, so the voltage applied to them is divided into 3 equal parts.
Generation of trigger control signals
Timer start
A reference voltage of 1 / 3U is applied to the direct input of the DA2 comparator, and the external timer start voltage Uref through pin 2 is applied to the inverse input of the comparator. In order to act on the input S of the flip-flop DD1 at the output of this comparator, it is necessary to obtain a high level. This is possible if the voltage Uzap will be within 0… 1 / 3U.
Even a short-term pulse of such a voltage will trigger the DD1 trigger and the appearance of a high voltage at the output of the timer. If the input Uref is affected by a voltage higher than 1 / 3U and up to the supply voltage, then no changes will occur at the output of the microcircuit.
Stop timer
To stop the timer, you just need to reset the internal trigger DD1, and for this, a high level signal R is generated at the output of the comparator DA1. Comparator DA1 is included in a slightly different way than DA2. The reference voltage of 2 / 3U is applied to the inverting input, and the control signal "Operation threshold" Uthr is applied to the direct input.
With this inclusion, a high level at the output of the comparator DA1 will occur only when the voltage Uthr at the direct input exceeds the reference voltage 2 / 3U at the inverting one. In this case, the DD1 trigger will be reset, and a low level signal will be set at the output of the microcircuit (pin 3). There will also be an opening of the "discharge" transistor VT3, which will discharge the timing capacitor.
If the input voltage is within 1 / 3U… 2 / 3U, none of the comparators will work, the state change at the timer output will not occur. In digital technology, this voltage is called "gray level". If you just connect pins 2 and 6, you get a comparator with trigger levels 1 / 3U and 2 / 3U. And even without a single additional detail!
Changing the voltage reference
Pin 5, designated in the figure as Urev, is designed to control the reference voltage or change it using additional resistors. Also, a control voltage can be supplied to this input, due to which it is possible to obtain a frequency or phase modulated signal. But more often this conclusion is not used, and to reduce the influence of interference it is connected to a common wire through a capacitor of small capacity.
The microcircuit is powered through pins 1 - GND, 2 + U.
Here is the actual description of the NE555 integral timer. The timer contains many different schemes, which will be discussed in the following articles.
Boris Aladyshkin
Continuation of the article:
Timers - NA555, NE555, SA555, SE555
1 Features
- Time range from microseconds to hours
- Astable or monostable modes
- Adjustable fill factor
- TTL - compatible output can be used as drain or source (up to 200 mA)
- Product meets MIL-PRF-38535 standard
2 Application
- Fingerprint biometrics
- Retinal biometrics
- RFID - readers
3 Description
These devices are designed to operate in precision timing circuits and can produce precise timing delays or oscillations. In time delay mode or monostable mode, the time interval is set by one external resistor or capacitor.
The threshold level and the switching level are located at two-thirds and one-third of the supply voltage, respectively. These levels can be changed by changing the voltage at the control pin. When to enter trigger a low level signal is applied, the timer is triggered and sends to the output output high voltage level. If the signal levels at the outputs trigger and threshold above the threshold level, then the trigger is triggered and sets a low voltage level at the output output... Output reset (reset) can override the voltage values \u200b\u200bon all other pins to start a new clock cycle. When to withdraw reseta low voltage level is applied, the flip-flop is reset and sets on the pin output too low voltage level. When the output goes low, the discharge pin is closed through the low impedance channel to ground.
The output circuit is capable of supporting up to 200mA current. It can operate with supply voltages from 5 V to 15 V. With a supply voltage of 5 V, the voltage levels at the outputs are compatible with TTL inputs.
| Serial number | Housing | Dimensions |
|---|---|---|
| xx555 | PDIP (8) | 9.81mm × 6.35mm |
| SOP (8) | 6.20mm × 5.30mm | |
| TSSOP (8) | 3.00mm × 4.40mm | |
| SOIC (8) | 4.90 mm × 3.91 mm |
6 Location and purpose of terminals
NA555 ... D or P housing NE555 ... D, P, PS, or PW housing
SA555 ... D or P body
SE555 ... D, JG, or P body (Top view)
SE555 ... FK package (NC - pins not used) | OUTPUT | I / O | Description | ||
|---|---|---|---|---|
| Name | D, P, PS, PW, JG | FK | ||
| NO. | ||||
| CONT | 5 | 12 | I / O | It controls the threshold voltage of the comparator, eliminates the need to connect a capacitor. |
| DISCH | 7 | 17 | O | When the transistor is open, the timing capacitor is discharged through it. |
| GND | 1 | 2 | – | Earth |
| NC | 1, 3, 4, 6, 8, 9, 11, 13, 14, 16, 18, 19 | – | Internally unconnected pins | |
| OUT | 3 | 7 | O | Timer output for load connection |
| RESET | 4 | 10 | I | When a low level voltage is applied to this pin, the timer is also reset on the terminals OUTand DISCH |
| THRES | 6 | 15 | I | Stopping the timer. When the tension is on THRES > CONT on conclusions OUTand DISCH low voltage level is set |
| TRIG | 2 | 5 | I | Start timer. When voltage is applied to TRIG < ½ CONT on conclusions OUTand DISCH high voltage level is set |
| V CC | 8 | 20 | – | Supply voltage, 4.5 V to 16 V. (SE555 18 V maximum) |
7 Specifications
7.1 Absolute maximum values
| Min. | Max. | Unit rev. | |||
|---|---|---|---|---|---|
| V CC | Supply voltage | 18 | AT | ||
| V I | Input voltage | CONT, RESET, THRES, TRIG | V CC | AT | |
| I O | Output current | ± 225 | mA | ||
| θ JA | D body | 97 | ° C / W | ||
| P body | 85 | ||||
| PS case | 95 | ||||
| PW case | 149 | ||||
| θ JC | Thermal resistance for enclosures | FK body | 5.61 | ° C / W | |
| JG body | 14.5 | ||||
| T J | Working temperature | 150 | ° C | ||
| Case temperature for 60 s. | FK body | 260 | ° C | ||
| Soldering temperature for the case within 60 s. | JG body | 300 | ° C | ||
(1) Absolute maximum values \u200b\u200bindicate limits that, if exceeded, could damage the device. Electrical specifications do not apply when operating the device outside of its stated operating conditions. Exposing the device to absolute maximum values \u200b\u200bover a long period of time may affect its reliability.
(2) All voltages are indicated with respect to earth.
(3) Maximum power dissipation is a function of T J (max), θ JA, and T A. for any admissible is equal to P D \u003d (T J (max) - T A) / θ JA
(4) Thermal resistance for enclosure calculated per JESD 51-7.
(5) Maximum power dissipation is a function of T J (max), θ JC, and T C. Maximum Allowable Power Dissipation for any admissible ambient temperature is equal to P D \u003d (T J (max) - T С) / θ JС... Operating at an absolute maximum T J of 150 ° C may affect reliability.
(6) Thermal resistance for housing calculated per MIL-STD-883.
7.2 Storage temperature
Outdoor operating temperature range (unless otherwise noted)
| MIN | MAX | Unit rev. | |||
|---|---|---|---|---|---|
| V CC | Supply voltage | NA555, NE555, SA555 | 4.5 | 16 | AT |
| SE555 | 4.5 | 18 | |||
| V I | Input voltage | CONT, RESET, THRES, and TRIG | V CC | AT | |
| I O | Output current | ± 200 | mA | ||
| T A | Outdoor working temperature | NA555 | –40 | 105 | ° C |
| NE555 | 0 | 70 | |||
| SA555 | –40 | 85 | |||
| SE555 | –55 | 125 | |||
7.4 Electrical characteristics
| Parameter | Test conditions | SE555 | NA555 NE555 SA555 |
Unit rev. | |||||
|---|---|---|---|---|---|---|---|---|---|
| MIN | TYP | MAX | MIN | TYP | MAX | ||||
| Voltage level at pin THRES | V CC \u003d 15 V | 9.4 | 10 | 10.6 | 8.8 | 10 | 11.2 | AT | |
| V CC \u003d 5V | 2.7 | 3.3 | 4 | 2.4 | 3.3 | 4.2 | |||
| Current through the THRES pin | 30 | 250 | 30 | 250 | nA | ||||
| Voltage level at the TRIG pin | V CC \u003d 15 V | 4.8 | 5 | 5.2 | 4.5 | 5 | 5.6 | AT | |
| T A \u003d -55 ° C to 125 ° C | 3 | 6 | |||||||
| V CC \u003d 5V | 1.45 | 1.67 | 1.9 | 1.1 | 1.67 | 2.2 | |||
| T A \u003d -55 ° C to 125 ° C | 1.9 | ||||||||
| Current through the TRIG pin | at 0 V on TRIG | 0.5 | 0.9 | 0.5 | 2 | μA | |||
| RESET voltage level | 0.3 | 0.7 | 1 | 0.3 | 0.7 | 1 | AT | ||
| T A \u003d -55 ° C to 125 ° C | 1.1 | ||||||||
| RESET current | at 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 at DISCH off-state | 20 | 100 | 20 | 100 | nA | ||||
| Switching voltage on DISCH open | V CC \u003d 5 V, I O \u003d 8 mA | 0.15 | 0.4 | AT | |||||
| Voltage at CONT | V CC \u003d 15 V | 9.6 | 10 | 10.4 | 9 | 10 | 11 | AT | |
| T A \u003d -55 ° C to 125 ° C | 9.6 | 10.4 | |||||||
| V CC \u003d 5V | 2.9 | 3.3 | 3.8 | 2.6 | 3.3 | 4 | |||
| T A \u003d -55 ° C to 125 ° C | 2.9 | 3.8 | |||||||
| Low output voltage | V CC \u003d 15 V, I OL \u003d 10 mA | 0.1 | 0.15 | 0.1 | 0.25 | AT | |||
| T A \u003d -55 ° C to 125 ° C | 0.2 | ||||||||
| V CC \u003d 15 V, I OL \u003d 50 mA | 0.4 | 0.5 | 0.4 | 0.75 | |||||
| T A \u003d -55 ° C to 125 ° C | 1 | ||||||||
| V CC \u003d 15 V, I OL \u003d 100 mA | 2 | 2.2 | 2 | 2.5 | |||||
| T A \u003d -55 ° C to 125 ° C | 2.7 | ||||||||
| V CC \u003d 15 V, I OL \u003d 200 mA | 2.5 | 2.5 | |||||||
| V CC \u003d 5 V, I OL \u003d 3.5 mA | T A \u003d -55 ° C to 125 ° C | 0.35 | |||||||
| V CC \u003d 5 V, I OL \u003d 5 mA | 0.1 | 0.2 | 0.1 | 0.35 | |||||
| T A \u003d -55 ° C to 125 ° C | 0.8 | ||||||||
| V CC \u003d 5 V, I OL \u003d 8 mA | 0.15 | 0.25 | 0.15 | 0.4 | |||||
| High output voltage | V CC \u003d 15 V, I OH \u003d –100 mA | 13 | 13.3 | 12.75 | 13.3 | AT | |||
| T A \u003d -55 ° C to 125 ° C | 12 | ||||||||
| V CC \u003d 15 V, I OH \u003d –200 mA | 12.5 | 12.5 | |||||||
| V CC \u003d 5 V, I OH \u003d –100 mA | 3 | 3.3 | 2.75 | 3.3 | |||||
| T A \u003d -55 ° C to 125 ° C | 2 | ||||||||
| Power consumption | V CC \u003d 15 V | 10 | 12 | 10 | 15 | mA | |||
| V CC \u003d 5V | 3 | 5 | 3 | 6 | |||||
| Low output level, no load | V CC \u003d 15 V | 9 | 10 | 9 | 13 | ||||
| V CC \u003d 5V | 2 | 4 | 2 | 5 | |||||
(1) This parameter affects the maximum values \u200b\u200bof the timing resistors R A and R B in the circuit. 12. For example, when V CC \u003d 5 V R \u003d R A + R B ≉ 3.4 MΩ, and for V CC \u003d 15 V, the maximum value is 10 mΩ.
7.5 Performance characteristics
V CC \u003d 5 V to 15 V, T A \u003d 25 ° C (unless otherwise noted)
| Parameter | Test conditions | SE555 | NA555 NE555 SA555 |
Unit rev. | |||||
|---|---|---|---|---|---|---|---|---|---|
| Min. | A type. | Max. | Min. | A type. | Max. | ||||
| Initial error time intervals | T A \u003d 25 ° C | 0.5 | 1.5 | 1 | 3 | % | |||
| Every timer, astable | 1.5 | 2.25 | |||||||
| Time Interval Temperature Coefficient | Each timer, monostable | T A \u003d MIN to MAX | 30 | 100 | 50 | ppm / ° C |
|||
| Every timer, astable | 90 | 150 | |||||||
| Change of time interval from supply voltage | Each timer, monostable | T A \u003d 25 ° C | 0.05 | 0.2 | 0.1 | 0.5 | % / V | ||
| Every timer, astable | 0.15 | 0.3 | |||||||
| Rise time of output pulse | C L \u003d 15 pF, T A \u003d 25 ° C |
100 | 200 | 100 | 300 | ns | |||
| Output pulse decay time | C L \u003d 15 pF, T A \u003d 25 ° C |
100 | 200 | 100 | 300 | ns | |||
(1) Meets MIL-PRF-38535 and has not been factory tested.
(2) For conditions specified as Min. and Max. , use the appropriate value specified in the recommended operating conditions.
(3) The time interval error is defined as the difference between measured value and average random sample from each process.
(4) Values \u200b\u200bare given for the monostable circuit shown in Fig. 9, with the following component values \u200b\u200bR A \u003d 2 from kΩ to 100 kΩ, C \u003d 0.1 μF.
(5) Values \u200b\u200bare given for the astable circuit shown in Fig. 9, with the following component values \u200b\u200bR A \u003d 1 from kΩ to 100 kΩ, C \u003d 0.1 μF.
7.6 Typical characteristics
Data for temperatures below -40 ° C and above 105 ° C only apply to SE555
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Fig. 1 Low level output voltage versus low level output current for 5V supply voltage.
Fig. 2 Low level output voltage versus low level output current for a 10 V supply voltage. 8 Delay time of signal propagation from a low level trigger pulse.8 Detailed description
8.1 Overview
The xx555 series timers are popular and easy to use and are often used to synchronize time intervals from 1 μs to hours or frequencies from<1 мГц до 100 кГц. В режиме временной задержки или моностабильном режиме заданный интервал регулируется одним внешним компонентом (резистором и конденсатором). В астабильном режиме работы частоту и коэффициент заполнения можно изменять независимо друг от друга двумя внешними резисторами и конденсатором.
8.2 Functional block diagram
- RESET can be replaced with TRIG, which can be replaced with THRES.
8.3 Description of characteristics
8.3.1 Monostable operation
To operate in monostable mode, any of the timers of this series can be connected as shown in Fig. nine.
Figure: 9 Connection diagram for monostable operation. |
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|
Figure: 10 Oscillogram of voltages for monostable operation.
Fig 11 The duration of the output pulse from the capacitance of the capacitor8.3.2 Unstable operation
Figure: 12 Connection diagram for an astable operating mode. 
Figure: 13 Oscillogram of voltages for an astable mode of operation. 9. Application
9.1 Information for use
The xx555 series timers use a resistor and capacitor to form the delay time or operating frequency. In this section provides simplified information for designing circuits.
9.2 Typical applications
9.2.1 Skip Pulse Indicator
Figure: 16 Skip Pulse Indicator Circuit 9.2.2 Design requirements
The input error (no pulse) should be large. A small input signal will not be detected as timing capacitor “C” will be discharged.
9.2.1.1 Detailed design description
Select the value of R A and C so that R A × C\u003e [maximum input pulse duration]. R L improves V OH, but is not required for TTL compatibility.
9.2.1.2 Voltage diagram
Figure: 17 Oscillogram of synchronization execution for the pulse skip indicator 9.2.2 555 PWM controller
The timer can be adjusted by changing the internal triggering threshold and switching, which is carried out by applying an external voltage or current to the CONT pin. Shown is a circuit for pulse width modulation. The continuous sequence of input pulses starts the monostable multivibrator, and the control signal modulates the threshold voltage. Shown is the resulting output pulse width modulation. While the sinusoidal modulating signal can be of any shape.
Figure: 18 Schematic of a PWM regulator for 555 Pin numbers shown are for D, JG, P, PS, and PW packages.
- The modulating signal can be connected directly or through a capacitor to the CONT pin. For direct connection, the effect of voltage and resistance of the modulation source on the timer deviation must be considered.
9.2.2.1 Design requirements
The sync input must supply V OL and V OH greater than and less than 1/3 of the supply voltage. The voltage at the input of the modulating signal must be varied relative to ground. The connected load must be tolerant of the non-linearity of the transfer function; the relationship between modulation and pulse width is not linear because the capacitor charge in the RC circuit follows a negative exponential curve.
9.2.2.2 Detailed design description
Choose R A and C so that R A × C \u003d 1/4 [sync period]. R L improves V OH, but is not required for TTL compatibility.
9.2.2.3 Voltage diagram
Figure: 19 Oscillogram of PWM modulation. 9.2.3 Pulse Phase Modulation
Shown is a 555 wiring diagram for operation as a phase-pulse regulator. This circuit adjusts the threshold voltage and thus the delay time associated with the unsynchronized oscillator. The triangle waveform for this circuit is shown; however, the signal can be of any shape.
Figure: 20 Connection diagram for pulse-phase modulation 9.2.3.1 Design requirements
The DC and AC current at the modulating signal input will change the upper and lower voltage thresholds of the timing capacitor. The frequency and duty cycle will change depending on the modulating signal.
9.2.3.2 Detailed design description
The rated output frequency and duty cycle can be calculated using the formula for an astable multivibrator. R L improves V OH, but is not required for TTL compatibility.
9.2.3.3 Voltage diagram
Figure: 21 Oscillogram of voltages for phase-pulse modulation 9.2.4 Sequential timer
Many devices such as computers require signals to initialize conditions during startup. Others, such as test equipment, require activating test signals in a pulse train. This circuit can be connected to provide such sequential control. The timers can be used in various combinations, both with astable and monostable wiring, with or without modulation, for extremely flexible waveform control. Shown is a series circuit that can be used in many systems, and the output voltage diagram is shown.
Figure: 22 Sequential timer at 555 9.2.4.1 Design requirements
A serial timer is a chain of several interconnected timers connected in a monostable circuit. The connected components are 33 kΩ resistors and 0.001 μF capacitors.
9.2.4.2 Detailed design description
The value of the timing capacitors and resistors can be calculated using the formula: t w \u003d 1.1 × R × C.
9.2.4.3 Voltage diagram
Figure: 23 Oscillograms of voltages at the outputs You don't need a controller, they said. Do it all on NE555 timers, they said. Well, I did - it seems, only to make sure that the result is a structure that is amazing in its crushing effect on my fragile psyche.
The review, if this text can be called that, will not be too long. Because it is only a statement of my complete and unconditional failure in the assembly of elementary circuits and a demonstration that at least six out of twenty chips are quite workable.
Also note: it looks like the store recently changed the rules, since now they have a minimum order with free shipping - from $ 6, and if less, then they will charge $ 1.5 for shipping. When I bought, they wrote off only the purchase price, that is, $ 0.59, and that's it.
There are exactly twenty pieces in two blisters. On the one hand, each blister is wrapped with tape, on the other, it is closed with a rubber stopper:
In general, initially I bought timers to make a simple generator for finding a short circuit in the wiring - my friends became interested. The essence of the device, if I understood correctly, is that the circuit to the short circuit is an antenna, the signal from which can be listened to with a conventional MW / LW receiver.
Where the squeak stopped, there is a short circuit. This is how it looks in practice from a friend, in whose footsteps I planned to follow:
But then the acquaintances with the need decided that they did not really need everything. Or else they decided something, but I did not insist. And to be upset too: you saw how much timers cost (a little more than half a dollar for 20 pieces) - what a chagrin?
Common DIP8:
Therefore, I decided to have some fun in another way and looked at what they generally make of NE555. And they do, as it turned out, a lot of everything. All sorts of alarms, voltage indicators, indicators of missed impulses. In general, I was impressed.
Well, since everyone describes about the same thing, here are a couple of Radio Cat links for you: and. Schemes - in the second.
It is assumed that the popularity of the NE555 is due to the fact that it is a design proven for years (more precisely, already 45 years), which is discouragingly simple to configure and quite accurately observes the characteristics regardless of the supply voltage, which can be in the range from 4.5V to 16V for the regular version (but there are options). That is, the voltage is walking, and the frequency is rather stable than not.
In fact, getting the timer to work requires a couple of parts and any suitable power source - very attractive to do some bullshit without too much hassle.
As for me, the problem with the microcontroller is even less, but in the comments to the story about the "Pistchal" I got and lost my peace. I realized that I should try at least to calm down.
So the idea was simple - a feeding timer for cats. Who, having lost all shame, began to demand food almost every half hour, and eating three crackers each, dispersed contentedly. In the opinion of the veterinarian, this is not very useful (and in our opinion it is also extremely troublesome), so it was necessary to return them to their diet. Well, as to the place: feed at least no more often than once every five to six hours.
Keeping track of the clock is certainly not difficult. However, firstly, the situation is complicated by the fact that if the feeding by the hour passes even more or less during the day, then at night it is no longer quite, since one cat, let's say, has a complex character. Exactly - he walks and scratches his claws on the battery, and even if I decided not to pay attention to this musical experiment of dubious quality, I feel sorry for the neighbors.
That is, at night you have to get up and time the time again, but in a semi-conscious state it is a little difficult.
Secondly, not all cats are so scandalous, so some simply do not come along with this troublemaker. And it turns out that the intervals are different for everyone, and in all fairness it would be nice to feed after a set time those who missed an extraordinary meal.
Therefore, I came up with a bunch of independent timers for a fixed time - one per cat. And so that like this: the cat comes, you give him food, you press the button, the light comes on. As the light goes out, the cat can be fed again.
As you might guess, this is one of the main options for the timer. It can be called in different ways: you can use a tracing paper from - monostable, you can - a single-vibrator, you can - a waiting multivibrator.
The essence of this does not change: the NE555 is required, in fact, to issue only one pulse of the required duration.
Therefore, I took the timer circuit from:
But I simplified it a little by getting rid of the trimmer (since I have a fixed interval) and the second LED as unnecessary. At the same time, I changed the values \u200b\u200bof the timing chain, checking everything with the same documentation, which says that to calculate the approximate pulse duration, you should use the formula y t \u003d 1.1RC.
After playing with the fonts with the denominations of the details available in the Chip-and-Dip boutique, I found that a 3300 uF capacitor and a 5.1 MΩ resistor are quite suitable for a five-hour interval that suits everyone:
T \u003d 1.1 * 0.0033 * 5100000 \u003d 18513 sec \u003d 5.14 hours.
The reality, however, turned out to be slightly inconsistent with theory. The timer assembled according to this scheme and with these denominations continued to work even after five hours. I didn't have the patience to wait until it was finished, so I assumed that the NE555 does not work very well with high ratings.
A quick googling showed that yes, it is possible, but there should have been no problems (theoretically) with a resistance of up to 20 megohms at a supply voltage of 15 V. Therefore, I continued the experiments and found out that in my case the formula turns out to be something like this:
And he was very grateful to himself that he bought not only 5.1 MΩ, but also, just in case, the nearest denominations - 4.7 MΩ and 3.9 MΩ. The latter, fortunately, just came up for the required interval.
With these ratings (3300 uF and 3.9 MΩ), I assembled a block of timers with bulbs and buttons. I connected everything with a common power line, they have no more points of contact (well, at least I tried not to). And since I was collecting the weights, I checked myself with a multimeter at every step and was almost calm when I started the first of the timers.
It turned out like this (I warned at the very beginning):
It turned on as expected, so I unsoldered the remaining buttons and lights, turned it on. I pressed the buttons. The LEDs turned on exactly as they should: press the button, turn on, and that's it.
And then I made a big mistake. I haven't done a few more test runs, but I was just upset that I didn't solder the wires to the buttons very well, and decided to rewire them. Therefore, I do not yet know what exactly happened: either I did something wrong initially, or I managed to spoil something at the time of soldering the wires.
But it turned out funny. When turned on again (with soldered wires), three LEDs immediately lit up. And pressing the buttons revealed complete chaos: you press one button - its LED lights up (i.e., in theory, the timer turns on), you press another - the first LED goes out, the second lights up. Etc.
Empirically, I found out that there is a certain combination of button presses in which all the LEDs are lit. But until the hands reach it, check the circuit for short circuits where they should not be.
Bonus track - play sapper:
Summing up, I want to say that I had fun with timers. In practice, I checked that it is possible to buy them in China - workers come.
And although he could not make a cat timer, he received a puzzle "Light all the lights" as a bonus. And at the same time, the understanding that NE555 is clearly not for me. And that's why:
Minimum supply voltage 4.5V
- high current consumption
Of course, these shortcomings can be overcome by ordering a CMOS version of the chip, which is much more economical and works from 1.5V. But ordinary ones cost $ 0.59 for twenty pieces, and CMOS - already about $ 10. That is, about twice the price of a controller, and if you use two or more timers in the design, then the benefit disappears altogether.
So thank you all, I'm going back to the ATmega328p, which will obviously be the one to do the feeding timer.
Ps. Now, can I also write about the screen from ITEAD Studio? By the way, my conscience torments me, because, on the one hand, there were already these screens above the roof, and on the other, I must keep my promise.
I plan to buy +19 Add to favourites I liked the review +38 +67
