Bistable multivibrator using 555 timer

Bistable multivibrator using 555 timer
Bistable multivibrator using 555 timer

You’ve been playing with circuits for years and think you understand them. You’re familiar with resistors, capacitors, and transistors, but you want to learn more sophisticated circuits with functionality. Buttercup, buckle up as we build a bistable multivibrator circuit using the 555 timer, everyone’s favorite integrated circuit. With a few common components, you can build a circuit with two stable output states that can switch between them. It’s essential for sequential logic and timing circuits. For those interested, we’ll examine the schematic, explain how it works step-by-step, discuss the timing math, and suggest modifications. Even if you’re new to integrated circuits, you’ll feel confident using the 555 by the end of this essay. Ready for a new electrical weapon? Read on!

What Is a Bistable Multivibrator?

A bistable multivibrator, or flip-flop circuit, is an electrical circuit with two stable states. Sequential logic circuits have two stable equilibrium points. One bit of state can be stored.Bistable multivibrators can use the 555 timer IC. The 555 latches to two stable states as a bistable multivibrator. It stays in any stable condition until triggered to switch. This cycling between states can generate oscillators, timers, and frequency dividers.

A simple 555 timer bistable multivibrator requires few components:

  • The 555 timer IC
  • Two resistors
  • One capacitor
  • SPDT switches

The two resistors set the 555 timer’s threshold and trigger voltages. The capacitor sets state transition timing. Manually switching the circuit state uses the SPDT switch.Flipping the switch activates one of the multivibrator’s stable states. The 555 timer will stay in that condition until the switch is switched again, causing the other stable state. Back-and-forth switching gives the multivibrator its name.

Simple memory, oscillator, and timer circuit. Use a few extra components to alter time for longer or shorter output pulses. The bistable multivibrator uses the 555 timer IC to provide clock signals, pulse-width modulation, and more.

How a 555 Timer IC Can Be Configured as a Bistable Multivibrator

A 555 timer IC can be a latch or flip-flop circuit, or bistable multivibrator. The 555 timer can latch into two stable states and stay in one until an external trigger switches it.

Building a bistable multivibrator using a 555 timer requires a few simple components:

  • The 555 timer IC
  • Two 10K-ohm resistors of identical value
  • Around 0.1 uF capacitor
  • Two push-button triggers
  • LED (status indicator)

How It Works

Output is high or low in the stable states. When a push button is pressed, the output changes. This circuit’s “memory” is the capacitor, which stores the prior state.

For instance, a low output turns off the LED. Trigger 1 (push button 1) turns on the LED by raising the output. Capacitor stores high state. Release the trigger and the output stays high and the LED stays on. Trigger 2 now. This lowers output, shutting off the LED. This low state is stored in the capacitor. And so on.

Pull-up and pull-down resistors determine high and low output states. Adjusting these resistors changes switching thresholds.

This circuit is used in counters, timers, and other applications that require a simple memory or latching function. A 555 timer chip lets you make one for a few dollars!

Circuit Diagram for a 555 Timer Bistable Multivibrator

Building a 555 timer bistable multivibrator requires only a few components. This circuit’s heart, the 555 timer IC chip, controls oscillation between two stable states. Frequency and duty cycle require capacitors and resistors.

Components needed:

  • 555 timer IC chip
  • 2 x 0.1 uF capacitors (104)
  • 2 x 1K ohm resistors (brown, black, red)
  • 2 x 10K ohm resistors (brown, black, orange)
  • LED (optional, for visual indicator)
  • Breadboard and jumper wires

Circuit diagram:

       10K   0.1uF  
   555   |   |   |   |   
       discharge  threshold
   GND | 1  2  3  4  5  VCC
       reset   output
       0.1uF   1K   LED  
   GND | 7  6  5  4  3  VCC    
       trigger   control  

Follow the diagram to connect breadboard components. The oscillation frequency and on/off timings are determined by two capacitors and four resistors. To vary time, try different resistor values.

The LED blinks as the 555 timer charges and discharges the capacitors when electricity is applied. The bistable multivibrator’s stable states are on and off. Adjusting resistor and capacitor values changes oscillator frequency and duty cycle.

A 555 timer can be used as an astable multivibrator to generate a square wave oscillator in this basic setup. A working timing circuit can be made with a few simple components! This circuit is useful for electronics enthusiasts and DIYers to learn by doing. Have more questions? Let me know!

Breadboard-Based 555 Timer Bistable Multivibrator

A breadboard-based 555 timer bistable multivibrator circuit requires a few basic components:

  • 555 timer IC
  • Two 1KΩ resistors
  • One 10KΩ resistor
  • One 0.1μF capacitor
  • Two LEDs (for visual output)
  • One breadboard
  • Hookup wires

Put the 555 timer IC on the breadboard. This chip controls timing and is the circuit’s heart. Next, connect a 1KΩ resistor from pin 2 to pin 6 and another from pin 6 to pin 7 of the 555 timer. These resistors accurately bias the internal flip-flop circuit.

Wire the 10KΩ resistor from pin 6 to pin 2. The resistor and 0.1μF capacitor connected from pin 2 to ground determine the delay between switching states.

Pin 3 is the bistable multivibrator output. One LED should be connected to ground and the other to the positive supply rail. These LEDs display flip-flop state.

Finish by connecting the positive supply to pin 8 and ground to pin 1. Use 5–15V DC to power the circuit.

To operate the bistable multivibrator, temporarily connect pin 2 to ground. This toggles the output between high and low, lighting the LEDs. The delay between state changes is set by the 10KΩ resistor and 0.1μF capacitor.

You may experiment with a bistable multivibrator timer circuit with a few simple pieces! Increase or reduce time delay by adjusting resistor and capacitor values. To control external devices, connect them to the output. Build your 555 timer circuit with fun!

Applications of 555 Timer Bistable Multivibrators

555 timer bistable multivibrators are useful in electronics projects. Simple latches and flip-flops are frequent uses. A bistable multivibrator can produce a simple memory storage circuit. Power the circuit, and it will store one bit of information in a set or reset state. Pulse the trigger input to set or reset the state. This circuit stores simple system flags or on/off settings.

Bistable multivibrators help make oscillators. Connecting the output to the trigger input generates a continuous stream of pulses at the RC timing components’ frequency. Change resistors or capacitors to change frequency. This 555 timer oscillator is helpful for clock signals, pulse width modulation, and other timing applications.

Simple analog switches can be made from 555 bistable multivibrators. High output conducts voltage. When low, it blocks voltage. Turning the output on and off with the trigger input routes an analog signal through the circuit. It works well as an analog gate or for basic logic tasks. pulsing output can trigger a relay to turn a motor on and off. Adjusting frequency controls motor speed. Braking is straightforward with the bistable setup—just switch the output to low or high to cut motor power.

The flexible 555 timer bistable multivibrator circuit can do all these things and more with a few more components. A inexpensive and reliable option for simple on/off control or pulse generation.


That’s it—a quick-to-build 555 timer bistable multivibrator circuit. With a few cheap parts, you can make a fun electronic project. You could connect an LED to make it flash. It can drive a small motor or relay. Building circuits is an excellent method to learn electronics and DIY skills, regardless of how you use it. When it succeeds, doing it cheaply makes it much more enjoyable. Grab an old 555, resistors, and caps from your components collection and start tinkering!

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