A Frequency to Voltage Converter Circuit (FVC) is an important part of signal processing, controlling motor speeds and connecting different sensors.
Its main job is to change a frequency signal it receives into a voltage output.
This makes it easier to measure and work with frequency as an analog voltage in many different uses.
This circuit works well with a power supply that provides between 10 to 15V DC.
In the diagram shown here, the TC9400 integrated circuit is set up as a frequency to voltage converter running smoothly on a single power supply.
The voltage output from this circuit directly relates to the frequency of the input signal.
This circuit uses the TC9400 integrated circuit which is known for its accuracy in converting frequency to voltage and vice versa.
It skillfully changes an input frequency signal into a DC voltage output that matches the input frequency.
Circuit Working:
Parts List:
| Component | Value | Quantity | Type |
|---|---|---|---|
| Resistors (1/4 Watt) | |||
| 470k | 1 | ||
| 33k | 1 | ||
| 100k | 1 | ||
| 10k | 2 | ||
| 1k | 2 | ||
| 1M | 2 | ||
| Preset Resistor | 100k | 1 | |
| Capacitors | |||
| Ceramic Capacitor | 0.01µF | 2 | |
| Ceramic Capacitor | 0.1µF | 1 | |
| Ceramic Capacitor | 47pF | 1 | |
| Ceramic Capacitor | 0.001µF | 1 | |
| Semiconductors | |||
| IC | TC9400 | 1 | |
| Zener Diode | 6.2V | 1 | |
| Diode | D2 = 1N914 | 1 |
The frequency signal you want to use should be connected to the Frequency IN terminal.
To reduce unwanted noise a resistor R4 and a capacitor C2 work together to filter the signal effectively.
The diode D2 is important for making sure the waveform is shaped correctly.
The IC TC9400 device changes the frequency into a voltage by creating a current that matches the input frequency.
The internal time constant is set by the combination of resistor R9 and capacitor C5.
Capacitor C4 (C ref) helps to stabilize the reference circuit.
The output voltage can be found at the Voltage OUT terminal and it directly relates to the input frequency.
To adjust the offset voltage for calibration a preset resistor VR1 is used.
The input frequency signal is connected to Pin 11 which is the input pin.
The signal is conditioned by R4, C2 and D2 to ensure the waveform is shaped properly.
Additionally, resistors R5 and R7 create a pull down network that helps with signal level shifting.
The signal at Pin 11 is then converted into a pulse signal which the integrated circuit uses for frequency to voltage conversion.
To make an adjustable reference voltage resistors VR1 and R2 form a voltage divider.
This adjustment is crucial for fine tuning the circuit making sure that when there is no input frequency the output voltage matches the correct baseline usually at 0V or another set reference point.
R8 (R bias) supplies a bias current to help the internal comparator circuit of the TC9400 work properly.
R9 (R Int Integration Resistor) is really important because it helps control how fast a frequency turns into voltage.
It works together with C5 (C Int integration capacitor) to smoothly combine the incoming frequency signal.
If you increase the resistance the time it takes to integrate gets longer which makes the response slower but smoother.
On the flip side if you lower the resistance the response gets faster, but it might cause more ups and downs in the output.
C5 (C Int Integration Capacitor) teams up with R9 to set the time constant for integration.
Together, C5 and R9 play a key role in deciding how stable the output voltage is and how quickly it reacts.
Using a bigger capacitor can make the output more stable but it might slow down the response time.
In contrast a smaller capacitor can speed up the response but it could also create some fluctuations in the output voltage.
Formulas with Calculations:
The formulas with calculations for Frequency to Voltage Converter Circuit using IC TC9400 is mentioned below:
The output voltage Vout is given by:
Vout = K × fin
where,
- K is a proportional constant determined by R9, C5 and the ICs internal characteristics
- fin is the input frequency
For practical design:
- Higher input frequency → Higher output voltage
- Lower input frequency → Lower output voltage
Example Calculation:
If the input frequency is 10 kHz and the proportional constant is 0.01 V/Hz then:
Vout =0.01 × 10,000 =100V
However, practical circuits are usually limited to an output of 0V to 10V or 0V to 5V requiring proper component selection.
How to Build:
To build a Frequency to Voltage Converter Circuit using IC TC9400 follow the below mentioned steps:
- Gather all the components as mentioned in the above circuit diagram.
- Connect pin 1 of IC1 TC9400 to GND through resistor R8
- Connect pin 2 of IC1 TC9400 to GND through resistors R2 and VR1 preset.
- Connect pin 3 of IC1 TC9400 one one end of resistor R9 and other end of resistor R9 to pin 12 of IC1.
- Connect pin 4 of IC1 to GND.
- Connect pin 5 of IC1 to one end of capacitor C4 and other end of capacitor to pin 3 of IC1
- Connect pin 6 of IC1 to one end resistor R1 and other end of resistor to pin 2, connect capacitor C1 from pin 6 and GND, connect D1 diode from pin 6 and GND.
- Connect pin 7 of IC1 to GND.
- Connect pin 11 of IC1 to frequency IN pin through capacitor C2 and resistor R4.
- Connect pin 12 of IC1 to voltage output through capacitor C5 and resistor R9
- Connect pin 14 of IC1 to V+ of 10V to 15V DC.
- Connect resistor R7 is connected between the junctions of resistor R5 and and R6.
- Connect diode cathode D2 from pin 11 and anode to one end of capacitor C3 and other end of C3 to GND
Conclusion:
This Frequency to Voltage Converter Circuit using IC TC9400 changes an input frequency into a matching voltage output.
You can adjust the circuit for various uses by choosing the right resistor and capacitor values.
When calibrated correctly it provides a precise and steady voltage output, which makes it a dependable choice for systems that measure analog signals based on frequency.
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