It only takes a minute to sign up. I'm trying to use an LM in a frequency to voltage converter configuration. I'm trying to implement this circuit from the datasheet for a supply voltage of 5V and an input frequency of Hz. Given my input signal frequency range, I'm trying to figure out how to set the full scale range of the frequency measurement. Page 3 of the data sheet says the the typical output range of pin 1 is 10uA to uA. This also means you can probably get a dynamic measurement range of Because uA is the maximum current, you'd want to choose a resistor that doesn't cause the output to hit the 5V end-stops so if you reckoned 2.
On the other hand, if you chose the circuit of figure 19 - the current output from pin 1 goes into a virtual earth op-amp circuit and therefore the restriction on impedance is of no importance any more - but obviously you have to obey the rule of not having so much gain in your op-amp circuit that the output hits the rails.
I think it's worth mentioning that although when operating as a voltage to frequency converter, a dynamic range of dB is attainable 1Hz to kHz you won't be able to get anything like this when operating as a frequency to voltage converter as mentioned above. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered.Diesel engine fuel consumption chart
Ask Question. Asked 6 years, 7 months ago. Active 6 years, 7 months ago. Viewed 7k times. LM block diagram: I'm trying to implement this circuit from the datasheet for a supply voltage of 5V and an input frequency of Hz. Joe Baker Joe Baker 1, 1 1 gold badge 15 15 silver badges 29 29 bronze badges. Active Oldest Votes. Andy aka Andy aka k 17 17 gold badges silver badges bronze badges.
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Related 4. Hot Network Questions.The LM family of voltage-to-frequency converters are ideally suited for use in simple low-cost circuits for analog-to-digital conversion, precision frequency-to-voltage conversion, long-term integration, linear frequency modulation or demodulation, and many other functions.
The output when used as a voltage-to-frequency converter is a pulse train at a frequency precisely proportional to the applied input voltage. Thus, it provides all the inherent advantages of the voltage-to-frequency conversion techniques, and is easy to apply in all standard voltage-to-frequency converter applications.
Features Related Document Register Login Checkout. Menu Special Pre-Book Deals. Modules Sensors Display Devices. Description Reviews 0 The LM family of voltage-to-frequency converters are ideally suited for use in simple low-cost circuits for analog-to-digital conversion, precision frequency-to-voltage conversion, long-term integration, linear frequency modulation or demodulation, and many other functions.
I've built a circuit with Shift lights and tachometer for a 4-cylinder engine. Everything is all right but how the LM works as a frequency to voltage converter? Can you explain me that if possible in french? Here is a scheme of the LM :. Last edited by a moderator: Dec 17, Scroll to continue with content.
3 Frequency to Voltage Converter Circuits Explained
Ron H Joined Apr 14, 7, Have you read the text on page 9 in the datasheetreferring to Fig. BTW, the part number is LM LM is a comparator. Last edited: Dec 15, Oh sorry : yes it's LM sorry Yes but I would like to know how this components works really?Like the ducklings followed their mother around the pond, certain electronics hobbyists are still going along with pre-wired China modules. As you may know, LM is a wonderful chip for voltage-to-frequency V-F conversion, and a superb component to start fiddling with analog electronics.
Luckily, we can also use the LM to build light intensity-to-frequency converter circuits. The circuit is in fact an adapted version of one application idea found in the official datasheet released by Texas Instruments www. In the basic light to frequency converter circuit shown above, one PTC 5mm silicon NPN phototransistor from Everlight is used as the light receiver T1. Anyway, you can try other compatible phototransistors for example, the SFH from Siemens here.
RC components R1 6. Note that the output frequency duty cycle, as well changes as the input light intensity changes, and the waveform driving the visual indicator LED1 can be taken from the point TP1 see the scope trace. Resistor R4 2KK is a pull-up resistor because the output pin 3 of IC1 is an open-collector terminal.
Resistor R5 R-1K sets the drive current for the red indicator LED1 which lights up entirely if the light receiver T1 gets zero light. As stated initially, the idea is pretty much cribbed from the datasheet. However, in my design of this light controlled variable frequency oscillator, I slowed the frequency down so we can see the visual blink i. LM is much simpler to interface and very linear. Today we can find cheap phototransistors and photodiodes both in 5mm LED plastic package.
Both the phototransistor and photodiode work on the background of inner photoelectric effect. In principle, a phototransistor uses normal transistor but with two terminals namely emitter E and collector Cwhereas in a photodiode ordinary PN junction diode which has anode A and cathode K terminals is used.
Phototransistor and photodiode pin assignments. The LM is ideally suited for use in simple inexpensive circuits good for analog-to-digital conversion and many other tasks. The output when used as a voltage-to-frequency or light-to-frequency converter is like a pulse train at a frequency precisely proportional to the voltage or signal at the input. Further, its input and output can be easily channeled with the help of a standard opto-isolator to provide perfect galvanic isolation. I may develop distinct ideas and write more on this later, but for now I can at least present experimental proof that it works.
Meanwhile, refer to the LM datasheet for more fascinating circuit ideas.Fixed header css
If the input voltage varies, the output frequency follows this and varies proportionately with a great degree of accuracy. The output from this IC could be expected to be highly immune to noise and with superb linearity.Ios run loops
The output conversion full-scale-range is determined with the inclusion of an external resistor and capacitor, which may be dimensioned to acquire a reasonably wide range of response. The device VFC32 is also equipped with a feature of working in the opposite manner, that is it may be configured to work like a frequency-to-voltage converter also, with similar accuracy and efficiency.
We will discuss about this in our next article in detail. The first figure below depicts a standard voltage to frequency converter circuit configuration where R1 is used for setting up the detection range of the input voltage. A 40k resistor may be selected for getting a 0 to 10V full scale input detection, other ranges could be achieved by simply solving the following formula:. Preferably R1 must be an MFR type for ensuring an improved stability. By adjusting the value of R1 one may trim down the available input voltage range.
However, it must be noted that the quality of C1 may directly affect or influence the output linearity or accuracy, therefore the use of a high quality capacitor is recommended. A tantalum perhaps becomes a good candidate for this type of application field. For higher ranges in the order of kHz and above, bigger capacitor may be opted for C1, while R1 may be fixed at 20k. The associated capacitor C2 does not necessarily produce an impact on the functioning of C1, however the value of C2 must not cross a given limit.Samsung j2 prime frp unlock tool
The value for C2 as shown in the figure below, should not be lowered, although increasing its value above this might be OK. The voltage to frequency converter circuit explained may be used for many user specific applications and could be customized for any relevant requirement.
One such application could be for making a digital power meter for recording the electricity consumption for a given load. The idea is to connect a current sensing resistor in series with the load in question and then integrate the developing current build-up across this resistor with the above explained voltage to frequency converter circuit. Since the current build up across the sensing resistor would be proportional to the load consumption, this data would be accurately and proportionately converted into frequency by the explained circuit.
The frequency conversion could be further integrated with a IC frequency counter circuit for getting the digital calibrated readout of the load consumption, and this could be stored for future assessment. The next high performance frequency to voltage converter circuit is built around a few components and an IC based switching circuit. With the part values indicated in the schematic, the ratio of conversion is achieved with a linear response of approx.
When an input voltage from 0 V V is applied it gets converted to a proportionate magnitude of 0 to 10 kHz square wave output voltage. Through the potentiometer P1the circuit could be tweaked to ensure that an input voltage of 0 V generates an output frequency of 0 Hz. The components responsible for fixing the frequency range are resistors R2, R3, R5, P1 along with the capacitor C2. Applying the formulae demonstrated below, the ratio of voltage to frequency conversion may be transformed in order that the circuit works extremely well for several unique applications.
LM331 IC - Precision Voltage to Frequency Converter IC
C2 you must ensure that this is always below one half of the minimum output period, meaning the positive output pulse should invariably be minimum as long as the negative pulse.As the name suggests frequency to voltage converters are devices that convert a varying frequency input into a correspondingly varying output voltage levels. This frequency voltage converter circuit using IC is characterized by its highly linear conversion ratio.
When a DC voltage is used at the input having 0 Hz frequency, the output generates a corresponding voltage of 0 V. The conversion ratio at the output is never affected by the duty cycle of the input square ave frequency.
But, if a sine wave frequency is applied at the input, in that situation the signal must be passed through a Schmitt trigger before introducing it to the IC input. If you are interested to have a different conversion ratio you may calculate it using the following formula:. The circuit can even be coupled to the output of a voltage to frequency converter and used as a way of sending DC signals across extended cable connection without the issues of cable resistance attenuating the signal.
The previous post explained a simple single chip voltage to frequency converter circuit using the IC VFC32, here we learn how the same IC could be used for achieving an opposite frequency to voltage converter circuit application. The figure below depicts another standard VFC32 configuration which enables it to work as a frequency to voltage converter circuit.
The input stage formed by the capacitive network of C3, R6 and R7 make the comparator input compatible with all 5V logic triggers. The comparator in turn toggles the associated one-shot stage on every falling edge of the fed frequency input pulses. The threshold reference input set for the detector comparator is around —0. As shown in the graph in the previous articlethe C1 value may be selected depending upon the full scale range of the frequency input triggers. C2 becomes responsible for filtering and smoothing the output voltage waveform, bigger values of C2 help to achieve better control over voltage ripples across the generated output, but the response is sluggish to rapidly varying input frequencies, whereas smaller values of C2 cause poor filtration but offer quick response and adjustment with the fast changing input frequencies.
R1 value could be tweaked for achieving a customized full scale deflection output voltage range with reference to a given full scale input frequency range. The basic operation of the proposed frequency to voltage converter circuit is based of a charge-and-balance theory. The result of this integration gives rise to a falling ramp integration output voltage. While the above takes place, the subsequent one-shot stage gets triggered, connecting the 1mA reference current with the integrator input in the course of the one-shot operation.
This in turn flips the output ramp response and causes it to climb upward, this continues while the one-shot is ON, and as soon as its period elapses the ramp yet again is forced to change its direction and causes to revert to the downward falling pattern. The above oscillating response process enables a sustained balance of charge average current across the input signal current and the reference current, which is solved with the following equation:.
The best possible application area for the above explained frequency to voltage converter circuit is where the requirement demands a translation of a frequency data into a voltage data. For example this circuit can be used in tachometersand for measuring speeds of motors in voltage ranges.
This circuit can be thus used for making simple speedometers for 2 wheelers including bicycles etc.Frequency to voltage converter is an electronic device which converts the sinusoidal input frequency into a proportional current or output voltage. The basic circuit includes operational amplifiers and RC circuits Resistor Capacitor networks. The operational amplifiers are used for signal processing.
And the RC networks are used to remove the frequency dependent ripples. The diagram below shows the basic circuit of frequency to voltage converter using op-amp and RC networks:. The input frequency given to this converter can be in the range of kHz. And the output can be between 0 to V.
The above block diagram shows a frequency to voltage converter.Trigonometric functions worksheet doc
The circuit charges the capacitor to a certain level. An integrator is connected in it and the capacitor discharges into this integrator or a low pass circuit. This happens for all the cycles of the input waveform. The precision switch and the monostable multivibrator generate a pulse of a specific amplitude and period which is fed into the averaging network. Hence we get a DC voltage at the output. This is the circuit diagram of frequency to voltage converter using LM This IC is basically a voltage to frequency converter but it can be used as a frequency to voltage converter.Arduino Interfacing TSL230R Light Frequency Converter
Its applications also include A to D conversion and long term integration. In this circuit, lm is used to convert frequency into voltage. The voltage on the output is proportional to the frequency at the input. It is an 8 pins IC.
2 Simple Voltage to Frequency Converter Circuits Explained
The source is connected to pin 8 and supplies 15V DC. Pins 3 and 4 are connected to ground. The input frequency is given at pin 6 and the output voltage is taken from pin 1. The input frequency is differentiated by using the resistor R7 and capacitor C3 and then the resultant pulse train goes to pin 6. The timer circuit gets triggered by the built-in comparator circuit in the IC when the negative edge of the pulse train appears at pin 6.
The current flowing out of pin 6 is proportional to the values of capacitor C1 and resistor R1 which are also known as the timing components and the input frequency. Therefore we get the output voltage across the resistor R4 which is proportional to the frequency of the input. The value of the resistor R3 is dependent upon the supply voltage. These converters are used in wide range of applications such as communication, power control, measurement and instrumentation systems etc.
A digital tachometer is an electronic device which measures the rate of rotation of a wheel. They display the rate of rotation in the form of voltage which is why a frequency to voltage converter is required in them. The diagram below shows a digital tachometer. The rate of occurrence of some events can be measured by a rate meter.
It counts the events for a certain time period and then divides the number of events by the total time and hence we get a rate. This is the theory of operation of a simple tachometer. We are using an IC LM for this tachometer circuit. The capacitors C1 and C2 and the resistor R1 have specific values according to the circuit requirements.
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