Frequency to Voltage Converter (F to V) Circuit using LM555 Timer

Usually, frequency to voltage converts (F to V converters) are commonly allied with digital tachometers. Digital tachometers are used to measure the rate of rotation of a wheel. These devices are currently available in a different types of forms which uses frequency to voltage converter. Most of the tachometers include reflective strip which is placed on the object to be measured. The frequency to voltage converter is used in many applications where repeating event  measurement requires like a wheel making a complete rotation. This F  to V converter is also used in place of the current encoders for the robots to measure velocity.

F to V Converter
F to V Converter

F to V Converter Circuit using LM555 Timer

LM555 Timer

LM555 IC
LM555 IC

The LM555 IC is a highly stable integrating circuit, that is used to produce precise oscillation or time delays. Extra terminals are provided for resetting or activating if desired. During time delay mode operation, the time is controlled by one external resistor or capacitor. The circuit may be activated & reset on falling waveforms, and the o/p circuit can source or drive TTL circuits.

LM555 Timer Pin Configuration

The LM555 timer comprises of 8-pins and function of the each pin are discussed below

555 Timer IC Pin Configuration
555 Timer IC Pin Configuration
  • Pin1 is a GND pin
  • Pin2 is a trigger pin, which is liable for conversion of the flip flop from set to reset. The timer’s o/p depending on the external trigger pulse amplitude which is applied to this trigger pin.
  • Pin3 is the output pin.
  • Pin4 is the reset pin. When the negative pulse is applied to this pin to reset the timer or disable, and false triggering can be avoided by connecting this pin to VCC.
  • Pin5 is the control voltage pin, this pin controls the trigger and threshold levels. This pin controls the pulse width of the o/p waveform. When an external voltage is applied, then the o/p waveform will be modulated.
  • Pin6 is the threshold pin, when the voltage is applied to this pin, then it compares with a reference voltage. The amplitude of this pin is responsible for the flip flop’s set state.
  • Pin7 is the discharge pin, when the open collector o/p discharges a capacitor among the intervals, then it toggles the o/p from high to low.
  • Pin8 is the V+ pin which is used to supply the voltage with respect to GND terminal.

LM555 Timer based Frequency to Voltage Converter Circuit

The F to V converter circuit requires a power supply circuit. For the below circuit.  This circuit uses a 12V DC supply for powering the owl circuit  In the power supply circuit diagram the D4 and D3 bridges can be made using diodes 1N4007, and 1A bridge rectifier modules also exist in the market.

F to V using LM555 Timer IC Circuit
F to V using LM555 Timer IC Circuit

The Frequency to voltage converter circuit diagram is shown belo. These circuits are used in many applications like tachometers, digital frequency meters, etc. This circuit mainly uses a LM 555 timer IC and it is wired in mono stable mode to change the i/p frequency into a fixed pulse width and variable frequency PWM (pulse width modulation) signal. Capacitor C2 and Resistor R4 afford the required timing for the circuit. The T1 transistor forms a discharge path parallel to C2 capacitor, which is required  for reactivating the IC and C1 capacitor performs as an i/p DC de-coupler.

  • This frequency to voltage Converter Circuit using LM555
  • Timer can be assembled on a Vero board.
  • It uses a 12V DC for driving the circuit.
  • LM555 timer IC must be attached to a holder.
  • The o/p of this circuit is not a pure DC but a PWM waveform.\
  • Extra circuitry is mandatory to convert this waveform from PWM to pure DC.

There are many features of using an LM555 timer in this circuit. Because, we can directly replace the SE555 or NE555. This IC operates in both astable and monostable modes. It has an adjustable duty cycle and the temperature stability is better than 0.005% per °C. The output of the LM555 timer IC is normally ON and normally OFF. It is available in the package of 8-pin VSSOP.

Some More F to V Converter Circuits

LM331 based frequency to voltage converter is a precise and compact circuit from national semiconductors. The circuit is extremely linear and has a very great dynamic range.The circuit operated from a single supply and can be easily assembled.

NE555 based F to V converter is one of the great application of IC NE555 timer. A simple  to V converter works from 12V DC. This circuit uses a maximum number of electronic components .

The applications of LM555 IC timer mainly involve in precision and sequential timing, generation of pulse and time delay, linear ramp generator, pulse width modulation and  pulse position modulation.

This is all about  frequency to voltage converter circuit using 555 timer which provides a straight forward guidelines to follow while making use of an item.In addition, the F to V converter circuit using the 555 IC online provide abundant knowledge about the several functions that are equipped with the item. Furthermore any queries regarding this concept or 555 timer projects please give your feedback in the comment section below.


  1. can i use 9v dc supply instead of 12?

    1. Tarun Agarwal says:

      Hi Alia
      yes, you can use


    Sir please send me the design of the circuit..

    1. Tarun Agarwal says:

      Hi Harikrishnan,
      Yes, we provide the Circuit diagram, Once the project has been purchased.
      The circuit diagram, code, and other information could be shared with you when you purchase the project.
      And also, can we know the title of your project?
      Meanwhile, please visit our website once:

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