Multivibrator Astable Menggunakan IC 555

Multivibrator is an electronic circuit that at a certain time only one of two output voltage levels, except during the transition period. The transition (switching) between the two levels of output voltage occurs quickly. Two state level of the multivibrator output voltage, which is stable and Quasistable.

Astable multivibrator is called when the output voltage levels generated by the multivibrator circuit is quasistable. The circuit will only change the state of the output voltage level between the 2 conditions, each state has a fixed period. Multivibrator circuit will work independently and no longer need a trigger. Period of time each output voltage level is determined by the components making up the circuit.

The picture above is the astable multivibrator circuit. This circuit will work when the voltage applied to Vcc ration and ground her. This circuit has two conditions are always changing with time. Because changing the type is known as astable multivibrator. With constant changes of 0 and 1, then the multivibrator is also called a bistable multivibrator (multivibrator which has two stable state of 0 and 1).


This change in cycle length can be calculated using the following equation:

Period = t1 + t2
t1 = 0.7 x (RA + RB) XC
t2 = 0.7 xRBxC.

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Rangkaian Multivibrator Monostable IC 555

Multivibrator Monostable IC 555

Rangkaian Multivibrator Monostable IC 555 is a pulse generator circuit in which the duration of the pulse is determined by the R-C connected to IC 555 timer. In such a vibrator, one state of output is stable while the other is quasi-stable (unstable). For auto-triggering of output from quasi-stable state to stable state energy is stored by an externally connected capaci tor C to a reference
level. The time taken in storage determines the pulse width. The transition of output from stable state to quasi-stable state is accom­plished by external triggering.

Capacitor C has to charge through resistance RA. The larger the time constant RAC, the longer it takes for the capacitor voltage to reach +2/3VCC. In other words, the RC time constant controls the width of the output pulse. The time during which the timer output remains high is given as

tp = 1.0986 RAC

where RA is in ohms and C is in farads. The above relation is derived as below. Voltage across the capacitor at any instant during charging period is given as

vc = VCC (1- e-t/RAC)

Substituting vc = 2/3 VCC in above equation we get the time taken by the capacitor to charge from 0 to +2/3VCC.

So +2/3VCC. = VCC. (1 – e-t/RAC) or t – RAC loge 3 = 1.0986 RAC

So pulse width, tP = 1.0986 RAC s 1.1 RAC

The pulse width of the circuit may range from micro-seconds to many seconds. This circuit is widely used in industry for many different timing applications.

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Rangkaian Timer dengan Alarm

The IC 4060 is a 14-stage ripple-carry binary counter/divider and oscillator with three oscillator terminals (RS, RTC and CTC), ten buffered outputs (O3 to O9 and O11 to O13) and an overriding asynchronous master reset input (MR). The oscillator configuration allows design of either RC or crystal oscillator circuits. The oscillator may be replaced by an external clock signal at input RS. The counter advances on the negative-going transition of RS.
A HIGH level on MR resets the counter (O3 to O9 and O11 to O13 = LOW), independent of other input conditions. Schmitt-trigger action in the clock input makes the circuit highly tolerant to slower clock rise and fall times.

Rangkaian Ic 4060 Timer Dengan Alarm

A timer circuit using IC 4060 is given here. The IC 4060 is a 14 stage binary counter with a built-in oscillator.R2, R7, C1 are the components that determine the frequency of the oscillator and the outputs will become high one after other and only one at a time. The last five outputs are only used here. The high pulses from the outputs are used to trigger the NE555 IC. Here NE555 is wired as a monostable multivibrator. The buzzer will produce the alarm when the output of IC2 goes high. The duration of the alarm depends on the components C3 and R5.The duration can be adjusted by varying the value of C3.The alarm will automatically turn OFF after the predetermined time. The trigger pin of IC2 will be normally positive. When the Q1 is forward biased by the positive pulse at its base from IC1, the capacitor C2 becomes charged and reduces the voltage at trigger pin of IC2.This triggers the IC.When the capacitor is fully charged the pin 2 becomes again positive.
The maximum duration from timer IC 4060 will be at pin 3. The times decrease by half in the pins 2, 3, 15, and 13 respectively. The timer duration can be varied by varying the capacitor C1.

Notes

• Use 6V DC for powering the circuit.
• Mount the ICs on holders.
• The switch S2 can be a single pole five throw rotary switch.
• The switch S1 can be a push button switch.
• S1 is used to reset the timer.
• S2 is used to select the alarm time.
• R7 can be used for the fine adjustment of alarm time.

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Rangkaian Variable frequency oscillator

Skema Rangkaian Variable frequency oscillator

555 timer IC provides practical solutions and relatively inexpensive for a variety of electronic applications related to the timing (timing). Especially two of the most popular application is a series of monostable and astable timing. The main components of this IC consists of comparators and flip-flop is realized with a lot of transistors.

The principle component of this type of work does not change but each manufacturer makes the IC design and technology different. Almost all manufacturers make this type of component, although with a different. For example National Semiconductor LM555 call it, Philips and Texas Instruments SE/NE555 call. Motorola / ON-Semi designed with CMOS transistors that power consumption was small enough and called it MC1455. Philips and Maxim make his version of the CMOS ICM7555 name. Although different names, but the function of each diagram and pin compatible with each other. It's just that there are several different specific characteristics such as power consumption, maximum frequency and so on.



HereNE55 is wired as an astable multivibrator ,whose out put frequency can be varied by varying a potentiometer.This circuit is a must in the work bench of a electronic hobbyist.Frequencies ranging from several Hz to several KHz can be obtained using this circuit.For very low frequencies (few Hz) replace C with a higher value electrolytic capacitor.
The values of R and C can be obtained using the following equations.
1/f = 0.69 * C * ( R1 + 2*R2).

% duty cycle = 100*(R1+R2)/(R1+ 2*R2) .The good option is to select R1 in K Ohms and R2 in M Ohms.

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Skema Rangkaian Oscillator LM555

LM555 Astable oscillator Circuit.

Circuit oscillator astable

Frequency of the output pulses is determined by the values of two resistors, R1 and R2 and by the timing capacitor, C.

To calculate the frequency (F):

To calculate the the On time or Off time:

Before calculating a frequency, you should know that it is usual to make R1=1 kΩ because this helps to give the output pulses a duty cycle close to 50%, that is, the HIGH and LOW times of the pulses are approximately equal.

LM555 Monostable oscillator Circuit.

circuit oscillator monostable

Trigger input is held HIGH by the 10 kΩ pull up resistor and is pulsed LOW when the trigger switch is pressed. The circuit is triggered by a falling edge, that is, by a sudden transition from HIGH to LOW. The trigger pulse, produced by pressing the button, must be of shorter duration than the intended output pulse.

To calculate the period (t):

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