NE556 Dual Bipolar Timer Features, Function, Structure, Working Principle, and Applications
08 December 2023
Ⅲ. What are the features of NE556 dual timer?
Ⅳ. Pin configuration of NE556 dual timer
Ⅴ. Function of NE556 dual timer
Ⅵ. Structure and working principle of NE556 dual timer
Ⅶ. Technical parameters of NE556 dual timer
Ⅷ. Touch dimmer circuit composed of NE556
Ⅸ. What are the applications of NE556 dual timer?
The NE556 integrated circuit is a highly stable controller capable of generating precise time delays or oscillations. It integrates two independent 555 timer circuits, which allows the NE556 to provide dual-channel timing functions on a single chip. In this article, we will introduce you to the features, pin configuration, function, working principle, structure and some important technical parameters and applications of NE556 dual timer.
Timer is a special type of clock used to calculate, control and record time values. It triggers a response at a precise time interval, which can be set by program or hardware. Once the set point of time is reached, the timer performs the intended operation.
It is mainly categorized into hold-type turn-on delay timers, pulse-type timers, turn-on delay timers and disconnect delay timers. Timer is not only applied to various life appliances, such as water boiler, water heater timing control, air conditioning timing switch, etc., but also can be applied to the military, such as time bomb, timing detonator, etc..
NE556 is a high-speed monolithic device or timer IC manufactured by Fairchild for generating time delays or oscillations. It is based on the 555 timer design with two separate running versions for oscillators and pulse generators. It requires only two external components to operate in unsteady or monostable mode. As a bipolar circuit, it has a high output drive capability of 200mA output current and an operating frequency range of up to 0.1Hz to 500kHz.
Replacements and equivalents:
• LM556
• CD4538
• CD4047
• NE556J
• SE556CN
• The output of NE556 can provide relatively high current.
• Its working state supports meso-stable and monostable modes.
• It is available in 14-pin SOIC, PDIP and VSSOP packages.
• NE556 has low off-time.
• NE556 allows users to adjust the timer frequency and duty cycle through external components (such as resistors and capacitors) to adapt to different application requirements.
• NE556 is able to operate normally over a wide range of temperatures.
The picture above shows the pin configuration of NE556. Among them, NE556 has a total of 14 pins, whose names and functions are as follows.
Pin 1&13 (Discharge): It is open collector output which discharges the capacitor (in phase with the output) during the interval. It switches the output from high to low when the voltage reaches 2/3 of the supply voltage.
Pin 2&12 (Threshold): We compare the voltage applied to the terminal with the reference voltage of 2/3 Vcc. The 6 I amplitude voltage applied to this terminal is responsible for the set state of the flip-flop.
Pin 3&11 (Control Voltage): It determines the pulse width of the output voltage I waveform. An external voltage applied to this pin can also be used to modulate the output waveform.
Pin 4&10 (Reset): A negative pulse applied to this pin is used to disable or reset the timer. When not used for reset 4 I purpose, we should connect it to VCC to avoid false triggering.
Pin 5&9 (Out): This pin is usually connected to the load as it is the only pin with an output drive waveform.
Pin 6&8 (Trigger): It is responsible for the transition of the trigger from set to reset. The output of the timer depends on the amplitude of the external trigger pulse applied to this pin.
Pin 7 (Ground): The ground reference voltage is 0V.
Pin 14 (Vcc): Supply voltage (Typ = 5V, Max = 18V).
• Anti-jitter: Using NE556 to generate appropriate delay can filter out the jitter in the input switch signal on the power amplifier panel to obtain a stable control signal.
• Generate PWM signals: NE556 can easily generate PWM pulse width modulation signals.
• Timing protection: Using NE556, you can implement timing protection for the power amplifier, such as setting a delay when powering on, allowing each component to stabilize before adding output to prevent inrush of large current or delay shutdown during shutdown, etc..
• Generate timing signals: NE556 can generate precise timing pulse signals to effectively control the circuit's working rhythm and timing, including starting the power amplifier and delaying shutdown.
NE556 is a bistable integrated circuit, which consists of a bistable flip-flop and a regulating circuit. A bistable flip-flop consists of two NPN transistors and one PNP transistor. When the input signal voltage exceeds a certain threshold, the flip-flop is activated, causing the output signal voltage to change. The regulating circuit includes an adjustable resistor and a fixed resistor. When the resistance of the adjustable resistor changes, the threshold of the input signal will be adjusted accordingly, thereby changing the activation voltage of the flip-flop.
The circuit can realize the brightness of the light from dark to bright after the light is turned on, and from bright to dark after the light is turned off. It uses the touch sheet and other components to achieve touch controllable. In addition to the touch chip, it requires an additional touch control circuit (optional SK-II IC). In addition, we need to choose a suitable "delay" circuit because the light-to-dark and dark-to-light are delayed on/off. Therefore, we can consider the use of a time-based IC, the NE556. Normally, the lamp is controlled by a direct connection between the thyristor and the lamp in order to achieve on/off control of the lamp circuit. However, in fact, the thyristor and the lamp to form the main circuit of the lamp control, while the touch film, touch control circuit, time-based integrated circuit NE556 and other components are composed of a secondary circuit, which together constitute the touch dimmer lamp circuit.
• Trigger: It can be used to build various types of trigger circuits, such as astable multivibrator.
• Electronic clock: By adjusting the parameters of its external components, it can control the time display and alarm clock and other functions.
• Electronic toys: The NE556 can enhance the fun and interactivity of electronic toys by generating different sound and light effects.
• Pulse Width Modulation (PWM): The NE556 can be used to generate PWM signals for applications such as controlling motor speed and adjusting LED brightness. The duty cycle of the PWM signal can be changed by adjusting the resistor and capacitor values of the timer.
• Timer: It can be used as a timer. By cooperating with external components, it can realize precise time measurement and timing operation.
• Musical equipment: The NE556 can be used in the design and production of musical equipment. It enhances the expressiveness and infectiousness of musical equipment by generating different tones and sound effects.
• Pulse generator: The NE556 can generate pulse signals. By adjusting the parameters of its external components, the frequency and duty cycle of pulses can be controlled to meet the needs of different applications.
Frequently Asked Questions
1. What is a 556 dual timer?
The NE556 dual monolithic timing circuit is a highly stable controller capable of producing precise time delays or oscillations. Operating as a time delay, the time is accurately controlled by one external RC (resistor/capacitor)network.
2. How does a 556 timer work?
The 556 consists of a pair of 555 timers in one package. The two timers work independently and only share common power supply connections. A typical example of a 556 circuit is shown here. The circuit drives a piezo sounder to provide a pulsed bleeping sound (similar to the reversing warning on many vehicles).
3. What is the difference between LM556 and NE556?
There is no difference between LM556 and NE556 except the source/sink current of the output pin. According to the LM556 TI datasheet, it is the direct replacement for NE556.
4. What is the NE556 IC used for?
The NE556 is used for timing and pulse generation applications, such as oscillators, pulse-width modulation, pulse position modulation, and time delay generation.
5. What is the difference between 555 and 556 timer?
The 556 is a dual version of the 555 housed in a 14-pin package, the two timers (A and B) share the same power supply pins. The circuit diagrams on this page show a 555, but they could all be adapted to use one half of a 556.
