Frequency to Voltage Converter Concept Based Project

Frequency to Voltage Converter IC Based Project:

Frequency to Voltage Converter Introduction:

• Inductive, reluctive and hall effect transducers produce switched outputs.
• That is, the output is normally held at some positive DC value untill the physical variable is sensed.
• Once it is sensed,the output falls to 0V.
• When these transducers and sensors are used to measure motion, the result is variable frequency pulse output.
• In order to be use these signals, the frequency must be converted to a proportional voltage or current.
• The circuits that perform this function are called as frequency to voltage converters and generally available as ICs.

In this post we are going to discuss about working principle and operation of these ICs, How to use these ICs to build our project? and one typical application. Once we understand completely about the IC, we can generate various  project ideas.

EXAR XR-4151, LM2907, LM2917 are some of the ICs available in the market which converts frequency into voltage. IC VFC32 will convert voltage into frequency and vice versa.

The block diagram of the XR-4151 is given below. Remember that almost all of the IC will have this same block diagram. Pin no may be different.

• As shown, there are four main components in the IC
(1) A comparator = It will compare the input value with the reference value. Please read more about opamp comparator operation.
(2) A one-shot = If the conditions meet, then it will trigger a pulse. it means, it will become active and produce a pulse.
(3) A constant current source
(4) An analog switch
• The principle of operation is very simple. The threshold input is usually biased at some voltage midway between 0V and VCC.
• When the signal at Vin exceeds the threshold, the output of the comparator switches to +SAT and triggers the one-shot.
• The the one-shot produces a pulse of duration based on the external RC circuit. The pulse enables the analog switch.
• The switch allows a short duration current pulse (of about 140μA) to pass through to the output.
• These output pulses can be filtered to produce a steady DC voltage.
• The constant current source and one-shot make the device output independent of the amplitude and duty cycle of the input signal.

we can build numerous projects and real-time applications by using this concept. One typical application using  LM2907 frequency to voltage converter IC is given below:

Once you get project ideas like this, you should ask following questions to yourself.

1. Where can I use this concept?
2. How to name the project differently?

The basic concept of the above typical application is

• The wheel will rotate when it is connected to any shaft or conveyor belt etc
• While rotating, the magnetic path intensity will increase and decrease (
• So the non inverting input of the comparator will vary
• If the wheel rotates fastly, more magnetic path, more input to the comparator.

Now a question for you.
Where can use this concept? Give some practical examples.

(Example: We can use this in textile industry where the wheel axis will connect with the thread holder. Whenever the bobbin pulls thread, the wheel will rotate.) Like this you can develop n number of real life situations.

Now give the project with catchy title. For the example given above we can name the project like:

Cost effective Thread measurement in textile industry using frequency to Voltage conversion Concept
(OR)
Innovative thread measurement/monitoring technique in textile industry.

We believe that this post will stimulate to think more and do your final year engineering project yourself.

You may also like to try the following mini Projects: