The NE555 integrated timer IC is a real breakthrough in electronics. It was created in 1972 by Hans R. Camenzind of Signetics. The invention has not lost its relevance to this day. The device later became the basis of the double (IN556N) and quad (IN558N) timers.
Without a doubt, the brainchild of an electronics engineer allowed him to occupy his prominent niche in the history of technical inventions. In terms of sales, this device has surpassed any other since its inception. In the second year of its existence, the 555 chip became the most purchased part.
Leadership remained in all subsequent years. The 555 chip, whose use increased every year, sold very well. For example, in 2003, more than 1 billion copies were sold. The configuration of the unit itself has not changed during this time. It has been in existence for over 40 years.
The appearance of the device came as a surprise to the creator himself. Kamenzind pursued the goal of making IP flexible in use,but that it would be so versatile, he did not expect. Initially, it was used as a timer or pulse generator. The 555 chip, which has grown rapidly in use, is now used from toys for children to spaceships.
The device is durable because it is built on the basis of bipolar technology, and nothing special is required to use it in space. Only test work is carried out with particular rigor. So, when testing the NE 555 circuit, individual trial specifications are created for a number of applications. There are no differences in the production of circuits, but the approaches to final control differ markedly.
The appearance of the circuit in domestic electronics
The first mention of innovation in the Soviet literature on radio engineering appeared in 1975. An article about the invention was published in the journal "Electronics". Chip 555, an analogue of which was created by Soviet electronics engineers in the late 80s of the last century, was called KR1006VI1 in domestic radio electronics.
In production, this part was used in the assembly of VCRs "Electronics BM12". But this was not the only analogue, since many manufacturers around the world created a similar device. All units have standard DIP8 package as well as small size SOIC8 package.
Circuit Specifications
The 555 chip, graphical representation of which is shown below, includes 20 transistors. On the block diagram of the devicethere are 3 resistors with a resistance of 5 kOhm. Hence the name of the device "555".
The main specifications of the product are:
- supply voltage 4.5-18V;
- maximum output current 200mA;
- energy consumption is up to 206 mA.
If you look at the output, then this is a digital device. It can be in two positions - low (0V) and high (4.5 to 15 V). Depending on the power supply, the indicator can reach 18 V.
What is the device for?
NE 555 chip - a unified device with a wide range of applications. It is often used in the assembly of various circuits, and this only makes the product popular. As a result, consumer demand rises. Such fame caused the price of the timer to drop, which pleases many masters.
Internal structure of timer 555
What makes this device function? Each of the outputs of the unit is connected to a circuit containing 20 transistors, 2 diodes and 15 resistors.
Double model format
It should be noted that the NE 555 (chip) comes in a double format called 556. It contains two free ICs.
The 555 timer has 8 pins while the 556 has 14 pins.
Device modes
The 555 chip has three modes of operation:
- Monostable mode of the 555 chip. It works like a one-way one-way. During operationa pulse of the specified length is emitted as a response to the trigger input when the button is pressed. The output remains low until the trigger is turned on. From here it also received the name waiting (monostable). This principle of operation keeps the device idle until it is turned on. The mode provides the inclusion of timers, switches, touch switches, frequency dividers, etc.
- Unstable Mode is a standalone feature of the device. It allows the circuit to stay in generator mode. The output voltage is variable: sometimes low, sometimes high. This scheme is applicable when it is necessary to set the device for jerks of an intermittent nature (with a short-term switching on and off of the unit). The mode is used when turning on LED lamps, functions in the clock logic, etc.
- Bistable mode, or Schmidt trigger. It is clear that it works according to the trigger system in the absence of a capacitor and has two stable states, high and low. A low trigger value goes to a high one. When the low voltage is released, the system rushes to the low state. This scheme is applicable in the field of railway construction.
Timer outputs 555
The generator chip 555 includes eight pins:
- Pin 1 (ground). It is connected to the negative side of the power supply (common wire of the circuit).
- Output 2 (trigger). It supplies high voltage for a while (it all depends on the power of the resistor and capacitor). This configuration is monostable. Conclusion 2controls pin 6. If the voltage in both is low, then the output will be high. Otherwise, if pin 6 is high and pin 2 is low, the timer output will be low.
- Pin 3 (output). Outputs 3 and 7 are in phase. Applying a high voltage of approximately 2 V and a low voltage of 0.5 V will produce up to 200 mA.
- Pin 4 (reset). The voltage supply to this output is low despite the 555 timer mode. To avoid accidental resets, this output should be connected to the positive side when in use.
- Conclusion 5 (control). It opens access to the comparator voltage. This output is not used in Russian electronics, but when it is connected, you can achieve a wide range of control options for the 555 device.
- Conclusion 6 (stop). Included in comparator 1. It is the opposite of pin 2, applicable to stop the device. This results in low voltage. This output can accept sine and square wave pulses.
- Pin 7 (digit). It is connected to the transistor collector T6, and the emitter of the latter is grounded. With the transistor open, the capacitor discharges before it closes.
- Pin 8 (positive power side), which is 4.5 to 18V.
Using Output
Output 3 (Output) can be in two states:
- Connecting a digital output directly to the input of another driver on a digital basis. The digital output can control other devices with a few additional components(power supply voltage is 0 V).
- Voltage reading in the second state is high (Vcc at power supply).
Machine Capabilities
- When the voltage in Output drops, current is directed through the device and connects it. This is the pulldown as the current is drawn from Vcc and flows through the unit to 0V.
- When Output increases, the current passing through the device ensures its inclusion. This process can be called the source of current. Electricity in this case is produced from the timer and goes through the device to 0 V.
Increase and decrement can function together. In this way, the device is switched on and off alternately. This principle is applicable to the operation of LED lamps, relays, motors, electromagnets. The disadvantages of this property include the fact that the device must be connected to Output in different ways, since output 3 can act both as a consumer and as a current source up to 200 mA. The power supply used must supply sufficient current for both devices and the 555 timer.
LM555 chip
Microcircuit 555 Datasheet (LM555) has a wide functionality.
It is used from square wave generators with a variable duty cycle and relays with a response delay to complex configurations of PWM generators. Chip 555 pinout and internal structure are shown in the figure.
The accuracy level of the fixture is 1% of the calculated indicator,which is optimal. A unit such as the NE 555 datasheet chip is not affected by ambient temperature conditions.
Analogues of the NE555 chip
Microcircuit 555, whose analogue in Russia was called KR1006VI1, is an integrated device.
Among the working blocks, we should highlight the RS flip-flop (DD1), comparators (DA1 and DA2), an output amplifying stage based on a push-pull system and complementing the transistor VT3. The purpose of the latter is to reset the time-setting capacitor when using the unit as a generator. The trigger is reset when a logical unit (Jupit/2…Jupit) is applied to the inputs R.
If the trigger is reset, the output of the device (pin 3) will have a low voltage indicator (transistor VT2 is open).
The uniqueness of the scheme 555
With the functional scheme of the device, it is very difficult to understand what is its unusualness. The originality of the device lies in the fact that it has a special trigger control, namely, it generates control signals. Their creation takes place on the comparators DA1 and DA2 (to one of the inputs, to which the reference voltage is applied). To generate control signals at the trigger inputs (comparator outputs), high voltage signals should be obtained.
How to start the device?
To start the timer, output 2 must be energized from 0 to 1/3 Jupiter. This signal contributes to the trigger, and a high voltage signal is generated when output. A signal above the limit will not cause any change in the circuit, since the reference voltage for the comparator is DA2 and is 1/3 Jupiter.
You can stop the timer when the trigger is reset. To this end, the voltage at output 6 must exceed 2/3 Jupit (the reference voltage for comparator DA1 is 2/3 Jupit). Resetting will set a low voltage signal and discharge the timing capacitor.
You can adjust the reference voltage by connecting an additional resistance or power source to the output of the unit.
Speedometer winding on 555 chip
Recently, it has become fashionable among car owners to wind up the mileage traveled by the car on the speedometer.
Many people are wondering if winding up a speedometer on a 555 microcircuit is doable?
This procedure is not particularly difficult. For its manufacture, a 555 microcircuit is used, which can function as a pulse counter. Individual components of the scheme can be taken with indicators deviating by 10-15% from the calculated values.
