Jameco 555 Timer Tutorial User Guide

Txuas Pin 1 (Ground) rau hauv av Circuit Court.
Apply a low-voltage pulse to Pin 2 (Trigger) to make the output (Pin 3) go high.
Use resistor R1 and capacitor C1 to determine the output duration.

Calculate R1 value using R1 = T * 1.1 * C1, where T is the desired timing interval.
Tsis txhob siv electrolytic capacitors rau lub sijhawm raug.
Use resistor values between 1K ohms and 1M ohms for standard 555 timers.

Txuas Pin 1 (Ground) rau hauv av Circuit Court.
Capacitor C1 charges through resistors R1 and R2 in astable mode.
Cov zis yog siab thaum lub capacitor them.
Cov zis mus qis thaum lub voltage hla C1 mus txog 2/3 ntawm cov khoom voltage.

Cov zis mus siab dua thaum lub voltage hla C1 poob qis dua 1/3 ntawm cov khoom siv voltage.
Grounding Pin 4 (Reset) stops the oscillator and sets the output to low.

Yuav Ua Li Cas Configure 555 Timer IC

555 Timer Tutorial
By Philip Kane
The 555 timer was introduced over 40 years ago. Due to its relative simplicity, ease of use and low cost it has been used in literally thousands of applications and is still widely available. Here we describe how to configure a standard 555 IC to perform two of its most common functions – as a timer in monostable mode and as a square wave oscillator in astable mode.

555 Timer Tutorial Bundle Includes

555 Signals and Pinout (8-pin DIP)

Figure 1 shows the input and output signals of the 555 timer as they are arranged around a standard 8 pin dual-in-line package (DIP).

Pin 1 - Hauv av (GND) Tus pin no txuas nrog hauv av.
Pin 2 – Trigger (TRI) A low voltage (tsawg dua 1/3 cov khoom voltage) siv sijhawm ib ntus mus rau qhov kev tawm tswv yim ua rau cov zis (pin 3) mus siab. Cov zis yuav nyob twj ywm siab kom txog thaum lub siab voltage yog siv rau qhov pib nkag (pin 6).

Pin 3 – Output (OUT) In the output low state the voltage will be close to 0V. In the output high state the voltage yuav yog 1.7V qis dua cov khoom voltage. Rau example, if the supply voltage yog 5V tso zis siab voltage 3.3v. Cov zis tso zis tuaj yeem tso lossis tso dej mus txog 200 mA (qhov siab tshaj plaws nyob ntawm cov khoom siv voltagthiab).

Pin 4 – Reset (RES) A low voltage (tsawg dua 0.7V) siv rau tus pin reset yuav ua rau cov zis (pin 3) mus qis. Cov tswv yim no yuav tsum txuas nrog Vcc thaum tsis siv.

Pin 5 – Control voltage (CON) Koj tuaj yeem tswj tau qhov pib voltage (pin 6) los ntawm kev tswj cov tswv yim (uas yog sab hauv teeb rau 2/3 cov khoom siv voltage). Koj tuaj yeem sib txawv ntawm 45% mus rau 90% ntawm cov khoom siv voltage. Qhov no ua rau koj sib txawv qhov ntev ntawm cov zis mem tes hauv hom monostable lossis cov zis zaus hauv hom astable. Thaum tsis siv nws raug pom zoo tias qhov kev tawm tswv yim no txuas nrog rau hauv av ntawm 0.01uF capacitor.
Pin 6 – Threshold (TRE) In both astable and monostable mode the voltage hla lub sij hawm capacitor yog saib xyuas los ntawm Threshold input. Thaum voltage ntawm qhov kev tawm tswv yim no nce siab tshaj qhov pib tus nqi cov zis yuav mus los ntawm siab mus rau qis.

Pin 7 – Discharge (DIS) when the voltage hla lub sij hawm capacitor tshaj tus nqi pib. Lub sij hawm capacitor raug tso tawm los ntawm qhov kev tawm tswv yim no
Pin 8 – Supply voltage (VCC) Qhov no yog qhov khoom zoo voltagib terminal. Cov khoom siv voltage ntau yam yog feem ntau ntawm +5V thiab +15V. Lub sijhawm RC lub sijhawm yuav tsis sib txawv ntau dua li cov khoom siv voltage ntau yam (kwv yees li 0.1%) hauv hom astable lossis monostable.

Monostable Circuit Court

Daim duab 2 qhia qhov yooj yim 555 timer monostable circuit.

Referring to the timing diagram in figure 3, a low voltage pulse siv rau qhov kev tawm tswv yim (pin 2) ua rau cov zis voltage ntawm tus pin 3 mus ntawm qis mus rau siab. Qhov txiaj ntsig ntawm R1 thiab C1 txiav txim siab ntev npaum li cas cov zis yuav nyob twj ywm siab.

During the timing interval, the state of the trigger input has no effect on the output. However, as indicated in Figure 3, if the trigger input is still low at the end of the timing interval, the output will remain high. Make sure that the trigger pulse is shorter than the desired timing interval. The circuit in figure 4 shows one way to accomplish this electronically. It produces a short-duration low-going pulse when S1 is closed. R1 and C1 are chosen to produce a trigger pulse that is much shorter than the timing interval.

As shown in figure 5, setting pin 4 (Reset) to low before the end of the timing interval will stop the timer.

Reset must return to high before another timing interval can be triggered.

Calculating the timing interval

Use the following formula to calculate the timing interval for a monostable circuit: T = 1.1 * R1 * C1
Where R1 is the resistance in ohms, C1 is the capacitance in farads, and T is the time interval. For example, if you use a 1M ohm resistor with a 1 micro Farad (.000001 F) capacitor the timing interval will be 1 second: T = 1.1 * 1000000 * 0.000001 = 1.1

Choosing RC components for Monostable operation

First, choose a value for C1.
The available range of capacitor values is small compared to resistor values. It’s easier to find a matching resistor value for a given capacitor.)
Next, calculate the value for R1 that, in combination with C1, will produce the desired timing interval.

Avoid using electrolytic capacitors. Their actual capacitance value can vary significantly from their rated value.
Also, they leak charge which can result in inaccurate timing values.

Instead, use a lower value capacitor and a higher value resistor. For standard 555 timers, use timing resistor values between 1K ohms and 1M ohms.

Monostable Circuit Example

Figure 6 shows a complete 555 monostable multivibrator circuit with simple edge triggering. Closing switch S1 starts the 5-second timing interval and turns on LED1. At the end of the timing interval LED1 will turn off. During normal operation switch S2 connects pin 4 to the supply voltage. To stop the timer before the end of the timing interval, you set S2 to the “Reset” position which connects pin 4 to ground. Before starting another timing interval you must return S2 to the “Timer” position.

Astable Circuit

Figure 7 shows the basic 555 astable circuit.

In astable mode, capacitor C1 charges through resistors R1 and R2. While the capacitor is charging, the output is high.
Thaum voltage hla C1 mus txog 2/3 ntawm cov khoom voltage C1 discharges through resistor R2 and the output goes low.
Thaum voltage hla C1 poob qis dua 1/3 ntawm cov khoom siv voltage C1 rov pib them, cov zis tawm mus siab dua thiab lub voj voog rov ua dua.
Daim duab lub sij hawm nyob rau hauv daim duab 8 qhia 555 timer tso zis nyob rau hauv astable hom.

Raws li pom nyob rau hauv daim duab 8, grounding lub Reset pin (4) nres lub oscillator thiab teev cov zis rau qis. Rov qab pib dua tus pin rau siab restarts oscillator.
Xam lub sij hawm, zaus thiab lub voj voog lub luag haujlwm Daim duab 9 qhia 1 lub voj voog ua tiav ntawm lub voj voog square uas tsim los ntawm 555 astable circuit.

The period (time to complete one cycle) of the square wave is the sum of the output high (Th) and low (Tl) times. That is: T = Th + Tl
qhov twg T yog lub sijhawm, hauv vib nas this.
You can calculate the output high and low times (in seconds) using the following formulas: Th = 0.7 * (R1 + R2) * C1 Tl = 0.7 * R2 * C1
or, using the formula below, you can calculate the period directly. T = 0.7 * (R1 + 2*R2) * C1
Txhawm rau nrhiav qhov zaus, tsuas yog siv qhov sib txuam ntawm lub sijhawm lossis siv cov qauv hauv qab no:

Qhov twg f yog nyob rau hauv cycles per second los yog hertz (Hz).
Rau example, nyob rau hauv astable circuit nyob rau hauv daim duab 7 yog R1 yog 68K ohms, R2 yog 680K Ohms, thiab C1 yog 1 micro Farad, zaus yog kwv yees li 1 Hz:

Lub luag haujlwm lub voj voog yog qhov percentage ntawm lub sij hawm uas cov zis yog siab nyob rau hauv ib tug ua tiav voj voog. Rau example, yog tias cov zis siab siab rau Th vib nas this thiab qis rau Tl vib nas this ces lub voj voog ua haujlwm (D) yog:

Txawm li cas los xij, koj tsuas yog xav paub qhov tseem ceeb ntawm R1 thiab R2 los xam cov dej num voj voog.

C1 tsub los ntawm R1 thiab R2 tab sis tso tawm los ntawm R2 ib leeg yog li lub voj voog ua haujlwm yuav ntau dua 50 feem pua. Txawm li cas los xij, koj tuaj yeem tau txais lub voj voog ua haujlwm ze ze rau 50% los ntawm kev xaiv qhov sib xyaw ua ke rau qhov xav tau zaus xws li R1 tsawg dua R2.
Rau example yog R1 yog 68,0000 ohms thiab R2 yog 680,000 ohms lub luag haujlwm lub voj voog yuav yog kwv yees li 52 feem pua:

Qhov me me R1 piv rau R2 qhov ze dua lub luag haujlwm lub voj voog yuav yog 50%.

Txhawm rau kom tau txais lub luag haujlwm lub voj voog uas tsawg dua 50% txuas lub diode nyob rau hauv parallel nrog R2.

Choosing RC components for Astable operation

Choose C1 first.
Calculate the total value of the resistor combination (R1 + 2*R2) that will produce the desired frequency.
Select a value for R1 or R2 and calculate the other value. For example, hais (R1 + 2 * R2) = 50K thiab koj xaiv 10K resistor rau R1. Tom qab ntawd R2 yuav tsum yog 20K ohm resistor.

Rau lub voj voog ua haujlwm ze li 50%, xaiv tus nqi rau R2 uas yog siab dua R1. Yog tias R2 loj npaum li cas rau R1 koj tuaj yeem pib tsis quav ntsej R1 hauv koj qhov kev suav. Rau example, xav tias tus nqi ntawm R2 yuav yog 10 npaug R1. Siv qhov hloov kho version ntawm cov qauv saum toj no los xam tus nqi ntawm R2:

Tom qab ntawd faib cov txiaj ntsig los ntawm 10 lossis ntau dua los nrhiav tus nqi rau R1.
Rau tus qauv 555 timers siv lub sij hawm resistor qhov tseem ceeb ntawm 1K ohms thiab 1M ohms.

Astable Circuit Example

Daim duab 10 qhia txog 555 square yoj oscillator nrog zaus ntawm kwv yees li 2 Hz thiab lub voj voog ua haujlwm ntawm kwv yees li 50 feem pua. Thaum SPDT hloov S1 nyob rau hauv "Start" txoj hauj lwm cov zis alternates ntawm LED 1 thiab LED 2. Thaum S1 nyob rau hauv lub "Stop" txoj hauj lwm LED 1 yuav nyob twj ywm thiab LED 2 yuav nyob twj ywm.

Tsawg zog versions

The standard 555 has a few characteristics that are undesirable for battery-powered circuits.
It requires a minimum operating voltage of 5V and a relatively high quiescent supply current.

During output transitions, it produces current spikes of up to 100 mA. Additionally, its input bias and threshold current requirements impose a limit on the maximum timing resistor value, which limits the maximum time interval and astable frequency.
Low-power CMOS versions of the 555 timer, such as the 7555, TLC555 and the programmable CSS555, were developed to provide improved performance, especially in battery-powered applications.
They are pin compatible with the standard device, have a wider supply voltage range (example, 2V to 16V for the TLC555) and require significantly lower operating current.

They are also capable of producing higher output frequencies in astable mode (1-2 MHz, depending on the device) and significantly longer timing intervals in monostable mode.
These devices have low output current capability compared to the standard 555. For loads greater than 10 – 50 mA (depending on the device) you will need to add a current boost circuit between the 555 output and the load.

Yog xav paub ntxiv

Consider this a short introduction to the 555 timer.
For further information, be sure to study the manufacturer’s data sheet for the specific part that you are using.

Also, as a quick Google search will verify, there is no shortage ntawm cov ntaub ntawv thiab tej yaam num devoted rau no IC ntawm lub web.
Rau example ,ua website provides more detail on both standard and CMOS versions of the 555 timer www.sentex.ca/~mec1995/gadgets/555/555.html.

FAQ

Q: Dab tsi yog lub hom phiaj ntawm Kev Tshawb Fawb thiab Kev Ua Haujlwm hauv 555 timer?

A: The Trigger input causes the output to go high when a low voltage is applied while the Threshold input stops the output from being high when a high voltage siv.

Q: Dab tsi yog qhov kev pom zoo ntawm qhov ntsuas qhov ntsuas rau lub sijhawm nyob rau hauv tus qauv 555 timer?

A: It is recommended to use resistor values between 1K ohms and 1M ohms for accurate timing in a standard 555 timer configuration.

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