Introduction of 555 Time Calculator
555 Timer Calculator is a great online 555 calculation tool for 555 timer circuits created by Utmel Electronic. With this 555 calculator, you are able to calculate the values of 555 timer integrated circuit. And this 555 IC Timer Calculator consists of two calculating features: 555 Astable Circuit Calculator and 555 Timer Monostable Calculator. In Monostable configuration, it acts as a 555 Timer Monostable Calculator, which can help Electronic designers to get the output pulse duration of 555 timer after entering the values of R1 resistor and C1 capacitance. However, in Astable mode, the 555 Timer Astable Calculator enables you to calculate the 555 timer circuit time high, time low and frequency.
555 Timer Astable Calculator Description
When a 555 timer is in Astable mode, we get a pulse on the output pin that can be monitored in terms of ON time (Time high) and OFF time (Time low). This can be accomplished by choosing the appropriate values for the resistors R1 and R2 as well as the capacitor C1. The circuit diagram to operate the 555 IC in Astable mode is shown below.
The circuit above can be used to generate a square wave from which the high (T1) and low (T2) times can be measured. This method can be used to produce clock pulses for Microcontrollers/Digital ICs, blink an LED, or perform any other task that requires precise time intervals. Markings on the output wave obtained from pin 3 are shown below.
The Voltage axis is measured in Volts and the Time axis is measured in seconds. As previously mentioned, the value of electronic components R1,R2 and C1 shown in the circuit diagram above can be used to determine how long the pulse stays high, how long the pulse stays low, and the frequency of the pulse.
555 Timer Monostable Calculator Description
The above 555 timer is set up as a monostable circuit. When a falling edge is detected on pin 2, the output voltage becomes high for a set duration (T) (trigger). A one-shot circuit is similar to the one shown above. The output pulse width of a 555 timer monostable circuit is calculated using this calculator.
The formula for the Output Pulse Width (T) is given as:
The output pulse width is solely determined by the resistor and capacitor combination, as shown in the formula. As a result, the circuit has a wide range of applications.
Depending on the values of resistor R and capacitor C, this 555 monostable circuit can generate pulses that last anywhere from a few microseconds to many hours. It should be noted, however, that the use of extremely large capacitor values (usually electrolytic-type) is discouraged. This is due to their broad tolerance limits, which means their true value differs significantly from their declared value. Another problem with such a capacitor is that it has a high leakage current, which can impair timing accuracy. If a large capacitance is needed, choose a tantalum form with a low leakage current.
When using small value capacitors to create very short delays, problems may arise. For values less than 100 pF, stray circuit capacitance will significantly alter the value of timing capacitance, resulting in an inaccurate timing.
Applications for Monostable Circuits
Touch Switch
A quick touch switch can be made out of the monostable circuit above. When the trigger pin is struck, a touch-plate may be attached to it, grounding the pin. The width of the pulse will be determined by the R and C combination at the output.
Servo Motor Tester
A servo motor accepts pulses with widths ranging from 1 to 2 milliseconds. By carefully choosing the R and C values to achieve the desired pulse widths, monostable circuits can be used to measure a servo motor.
What is a 555 Timer IC
The 555 Timer IC is a widely used integrated circuit (chip) with a square waveform output. Generally, 555 Timer circuit is applied in oscillator, pulse generation, delay and timer. And The output will be a free-running squarewave in the Astable configuration. The output in Monostable mode is a single high pulse produced for a single input case.
Besides, different manufacturers have different 555 timer chip designs. And the standard 555 timer ICs are packed with 15 resistors, 25 transistors and 2 diodes. And those electronic components are set on a silicon chip with DIP-8 (8-pin dual in-line package).
How Does a 555 Timer Work?
The above Youtube Video is created by How To Mechatronics to show us how the 555 Timer works. The charging and discharging timing of capacitors that are provided with resistance to either shunt it or ground it is crucial to the operation of 555 timers. On time refers to the amount of time the capacitors are charged to a specific voltage [1/3rd or 2/3rd of Vcc], whereas off time refers to the amount of time it takes to discharge the capacitors through resistance. As a result, the duty cycle may be simply calculated.
On the internet and in books, there are many different types of graphs and circuits to choose from. The primary idea is to figure out how long it takes to charge and how long it takes to discharge.
They are classed as Monostable or Astable based on their stable states of on time, with usable times of 1.1 RC and 0.693(R1+R2)C, respectively. It's worth noting that they always produce a rectangle [or square] voltage waveform. They're named 555 Timer because they have 3 5K ohm resistors in series in front of the comparators. Without R and C, I present a skeletal framework for an 555 IC timer.
555 Timer Pinout
| 555 Timer IC Pinout | |||
| PIN Number | PIN Name | PIN Function | PIN Description |
| 1 | GND | Ground reference(0V) | Voltages are measured with respect to this terminal |
| 2 | TRIG | To give external trigger voltage | Inverting input to the comparator, responsible to Set or Reset Flip-Flop |
| 3 | OUT | 1.7V below +VCC or to GND | Output of timer, load can be connected between this pin and ground |
| 4 | RESET | To reset timing interval | To disable or reset the timer, negative pulse is applied to this pin. If not using reset pin, it must be connected to +Vcc |
| 5 | CTRL | Provides control access to internal voltage divider | To control the threshold and trigger levels |
| 6 | THR | Threshold voltage | Non-inverting input to the comparator |
| 7 | DIS | In phase with output | Connected intermally to the collector of transistor, mostly a capacitor is connected between this terminal and ground |
| 8 | VCC | Positive voltage supply | Supply voltage of +5V to +18V is applied to this pin with respect to ground |
Related Products of 555 Timer/556 Timer/558 Timer
IC NE555 Timer
NE555 Timer IC is a single precision Timer. The first NE555 circuit is made by Signetics. Now, Texas Instruments also manufactures the NE555 IC Oscillators. And Signetics also produces NE556 and NE558. But the NE558 timer is discontinued. These are precision timing circuits that may generate precise time delays or oscillations. The timed interval is regulated by a single external resistor and capacitor network in the time-delay or mono-stable mode of operation. With two external resistors and a single external capacitor, the frequency and duty cycle may be regulated independently in the a-stable mode of operation.
Normally, the threshold and trigger values are two-thirds and one-third of VCC, respectively. The control-voltage terminal can be used to change these values. The flip-flop is configured and the output goes high when the trigger input falls below the trigger level.
The flip-flop is reset and the output is low if the trigger input is above the trigger level and the threshold input is above the threshold level. The reset (RESET) input has the ability to override all other inputs and start a fresh time cycle. The flip-flop is reset when RESET is low, and the output is low. A low-impedance channel is provided between discharge (DISCH) and ground when the output is low.
The output circuit has a current sinking and sourcing capability of up to 200 mA. The operation is limited to supply ranging from 5 to 15 volts. The output levels are compatible with TTL inputs when powered by a 5-V source.
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