Electronic Circuits and Diagram-Electronics Projects and Design

CircuitsToday is listing some simple 555 timer circuits that have already been published in our site before. To know about the basics of NE 555 along with the timer circuit schematic, click on the links below. 555 Timer Circuit Schematic and Working Principle 555 Timer Monostable Circuit 555 Timer Oscillator Circuit 555 as an Astable Multivibrator LM 555 Datasheet From the articles above you will also get the idea about its duty cycle and also other 555 timer applications. Here are the links of some easy 555 IC circuits with complete description and circuit diagram. A small description is given…

Ramp Generator Circuit-using 555 Timer IC We know that if a capacitor is charged from a voltage source through a resistor, an exponential waveform is produced while charging of a capaci­tor from a constant current source produces a ramp. This is the idea behind the circuit. The circuit of a ramp generator using timer 555 is shown in figure. Here the resistor of previ­ous circuits is replaced by a PNP transistor that produces a constant charging current. Charging current produced by PNP constant current source is iC = Vcc-VE / RE where VE = R2 / (R1 + R2) *…

A voltage-controlled oscillator (VCO) using the timer 555 is shown in figure. The circuit is sometimes called a voltage-to-frequency converter because the output frequency can be changed by changing the input voltage. As discussed in previous blog posts, pin 5 terminal is voltage control terminal and its function is  to control the threshold and trigger levels. Normally, the control voltage is ++2/3VCC because of the internal voltage divider. However, an external voltage can be applied to this terminal directly or through a pot, as illustrated in figure, and by adjusting the pot, control voltage can be varied. Voltage across the timing capacitor…

A monostable multivibrator (MMV) often called a one-shot multivibrator, is a pulse generator circuit in which the duration of the pulse is determined by the R-C network,connected externally to the 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 capaci­tor 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. The schematic of a 555…

An astable multivibrator, often called a free-running multivibrator, is a rectan­gular-wave generating cir­cuit. Unlike the monostable multivibrator, this circuit does not require any ex­ternal trigger to change the state of the output, hence the name free-running. Before going to make the circuit, make sure your 555 IC is working. For that go through the article: How to test a 555 IC for working An astable multivibrator can be produced by adding resistors and a capacitor to the basic timer IC, as illustrated in figure. The timing during which the output is either high or low is determined by the externally…

  Block Diagram of 555 timer IC: Comparator 1 has a threshold input (pin 6) and a control input (pin 5). In most applications, the control input is not used, so that the control voltage equals +2/3 VCC. Output of this comparator is applied to set (S) input of the flip-flop. Whenever the threshold voltage exceeds the control voltage, comparator 1 will set the flip-flop and its output is high. A high output from the flip-flop saturates the discharge transistor and discharge the capacitor connected externally to pin 7. The complementary signal out of the flip-flop goes to pin 3,…

  Block diagram for the 555 timer is given in figure. As shown in the block diagram, a 555 timer consists of two comparators (simply op-amps), an R-S flip-flop, two transistors and a resistive network Resistive network consists of three equal resistors and acts as a voltage divider. Comparator 1 compares threshold voltage with a reference voltage + 2/3 VCC volts. Comparator 2 compares the trigger voltage with a reference voltage + 1/3 VCC volts. Output of both the comparators is supplied to the flip-flop. Flip-flop assumes its state according to the output of the two compa­rators. One of the…

The 555 timer combines a relaxation oscillator, two comparators, an R-S flip-flop, and a discharge capacitor.   R-S Flip-Flop. A pair of cross-coupled transistors is shown in figure. Each collector drives the opposite base through resistance RB. In such circuit one transistor is saturated while the other is cut-off. For instance, if transistor Q1 is saturated, its collector voltage is almost zero. So there is no base drive for transistor Q2 and it goes into cut-off and its collector voltage approaches + VCC. This high voltage produces enough base current to keep transistor Q1 in saturation. On the other hand…

The 555 Timer IC is available as an 8-pin metal can, an 8-pin mini DIP (dual-in-package) or a 14-pin DIP. This IC consists of 23 transistors, 2 diodes and 16 resistors. The explanation of terminals coming out of the 555 timer IC is as follows. The pin number used in the following discussion refers to the 8-pin DIP and 8-pin metal can packages.   Pin 1: Grounded Terminal. All the voltages are meas­ured with respect to this terminal. Pin 2: Trigger Terminal. This pin is an inverting input to a comparator that is responsible for transition of flip-flop from set…

A complete basic tutorial of 555 Timer IC. This article covers every basic aspect of 555 Timer IC. You may already know that SE/NE 555 is a Timer IC introduced by Signetics corporation in 1970′s. In this article we cover the following information about 555 Timer IC. 1. Introduction to 555 Timer IC 2. 555 Timer IC Pin Configuration 3. Basics of 555 Timer 4. Block Diagram 5. Working Principle 6. Download Data Sheet 1. Introduction 555 timer IC One of the most versatile linear ICs is the 555 timer which was first introduced in early 1970 by Signetic Corporation…