AB29 F-V and V-F Converter Analog Lab Ver. 1.0 QUALITY · PDF fileF-V and V-F Converter Analog Lab Ver. 1.0 ... When a signal change occurs, the LM331's input comparator sets an internal

AB29F-V and V-F Converter

Analog Lab

Ver. 1.0

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AB29

Tel.: 91-731-2570301 Fax: 91-731-2555643Email: [email protected] Web: www.scientech.bz

Scientech Technologies Pvt. Ltd. 2

http://www.scientech.bz/

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AB29


AB29


AB29

F-V and V-F Converter

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Table of Contents

1. Introduction 4

2. Theory 6

3. AB29 Board Interpretation 10

4. Experiment 1 11To study the operation of LM331 as V-F Converter.

5. Experiment 2 14To study the operation of LM331 as F-V Converter.

Datasheet 17

6. Warranty 19

7. List of service Centers 20

8. List of Accessories with AB29 20

9. Notes 21


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Introduction

AB29 is a compact, ready to use F-V and V-F Converter experiment board. This board is useful for students to understand the working and operation of LM331 as Frequency to Voltage converter and Voltage to Frequency Converter. It can be used as stand alone unit with external DC power supply or can be used with SCIENTECH Analog Lab ST2612 which has built in DC power supply, AC power supply, function generator, modulation generator, continuity tester, toggle switches, and potentiometer.

List of Boards :

Model Name

AB01 Diode characteristics (Si, Zener, LED)AB02 Transistor characteristics (CB NPN)AB03 Transistor characteristics (CB PNP)AB04 Transistor characteristics (CE NPN)AB05 Transistor characteristics (CE PNP)AB06 Transistor characteristics (CC NPN)AB07 Transistor characteristics (CC PNP)AB08 FET characteristicsAB09 Rectifier CircuitsAB10 Wheatstone BridgeAB11 Maxwell’s BridgeAB14 Darlington PairAB15 Common Emitter AmplifierAB16 Common Collector AmplifierAB17 Common Base AmplifierAB18 Cascode AmplifierAB19 RC-Coupled AmplifierAB20 Direct Coupled AmplifierAB21 Class a AmplifierAB22 Class B Amplifier (push pull emitter follower)AB23 Class C Tuned AmplifierAB25 Phase Locked Loop (FM Demodulator & Frequency

Divider / Multiplier)AB28 Multivibrator (Mono stable / Astable)AB30 V-I and I-V ConverterAB31 Zener Voltage Regulator AB32 Transistor Series Voltage RegulatorAB33 Transistor Shunt Voltage Regulator


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AB41 Differential Amplifier (Transistorized)AB42 Operational Amplifier (Inverting / Non-inverting /

Differentiator)AB43 Operational Amplifier (Adder/Scalar)AB44 Operational Amplifier (Integrator/ Differentiator)AB45 Schmitt Trigger and ComparatorAB51 Active filters (Low Pass and High Pass)AB52 Active Band Pass Filter AB53 Notch Filter AB54 Tschebyscheff FilterAB56 Fiber Optic Analog LinkAB65 Phase Shift OscillatorAB66 Wien Bridge OscillatorsAB67 Colpitt OscillatorAB68 Hartley OscillatorAB80 RLC Series and RLC Parallel Resonance AB81 Kirchoff’s Laws (Kirchhoff’s Current Law & Kirchhoff’s

Voltage Law)AB82 Thevenin’s and Maximum power Transfer TheoremAB83 Reciprocity and Superposition TheoremAB84 Tellegen’s TheoremAB85 Norton’s theoremAB88 Diode ClipperAB89 Diode ClampersAB90 Two port network parameterAB91 Optical Transducer (Photovoltaic cell)AB92 Optical Transducer (Photoconductive cell/LDR)AB93 Optical Transducer (PhotoTransistor)AB96 Temperature Transducer (RTD & IC335)AB97 Temperature Transducer (Thermocouple)AB101 DSB Modulator and DemodulatorAB102 SSB Modulator and DemodulatorAB106 FM Modulator and Demodulator

………… and many more


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Theory

Voltage-to Frequency Converter :

A Voltage-to-Frequency converter converts dc voltage variation into proportional frequency depending on the circuit arrangement (RtCt value).

To perform the particular operation we have used IC LM331 along with the Op-amp circuit in feedback for the precise conversion of voltage into frequency. The circuit is as shown in fig.1. To understand the operation of the circuit it is necessary to understand the functional block diagram of LM331 which is as shown in fig.2

Voltage to Frequency ConverterFig. 1

As shown in fig.2 the voltages at pin no. 6 and 7 are fed to the input comparator (U1 on AB29 Board). Pin no. 6 is the threshold pin which is at fixed dc voltage (fig.1) and feedback voltage from op-amp integrator is applied to the pin no.7. When this voltage (pin no.7 voltage) exceeds threshold the R-S flip-flop is triggered which drives the output driver transistor (within O/P driver & Protection Circuit), thus, pulling down the pin no.3 to ground. Also the reset transistor (Switch S2) is cutoff and allows the external capacitor Ct at pin no.5 to charge through Rt. The pin no.5 is the input to another comparator, the timer comparator (U2 on AB29 board). The timer comparator threshold voltage is internally set to 2Vs/3 by R-2R network.


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Functional Block DiagramFig. 2

As the Ct voltage rises to 2VS/3 the comparator is triggered and thus resetting the R-S flip-flop. This will consequently drive the output driver transistor (within O/P drive & Protection Circuit) to cutoff, thus pulling output voltage to high level. When the R-S flip-flop is set, it allows the current switch to move to the position (Position shown on AB29 board) shown in fig.2. The switch is connected to a precision current reflector circuit which is actually a current mirror circuit. Depending on the resistance value at pin no.2 the current output at pin no.1 can be controlled. There is an accurate, internal band-gap source of 1.9V that is buffered by the op-amp and supplied to pin no.2. Any current leaving this pin is sent to current mirror, and is accurately copied as Is. As it also controls the bias current to all circuit the pot at pin no.2 can be used to adjust the final gain of the circuit. Also the value t limits the highest frequency that can be obtained and t can be calculated as,

t = 1.1 * Rt * Ct ………… (1)


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Output WaveformFig. 3

Integration is performed using conventional op-amp and feedback capacitor Cf (as shown in fig.1). When the integrator’s output crosses the nominal threshold level at pin no.6, the timing cycle is initiated. The average input fed into the op-amp’s summing point (pin no.2) is

I*(1.1 * Rt* Ct) * f

which is perfectly balanced with –Vin/Rin. The op-amp feedback dose not allow the offset voltage of input comparator to affect the offset or accuracy of V-F converter and offset current or bias current. Instead the offset voltage and current of op-amp are the only limits on how small the signal can be accurately converted. This circuit also responds immediately to any change in the input signal so that the output frequency will be an accurate representation of Vin. The output frequency can be given by the equation

- Vin * Rs

Fout = (Hz) (2.09V) * Rt * Ct * Rin ……… (2)

Where, Rin = 100K (internally connected to the input of integrator)

Frequency-to-Voltage Converter :

A Frequency-to-Voltage converter converts frequency variation into proportional dc voltage depending on the circuit arrangement (RtCt value).

To perform the particular operation we have used LM331 IC which gives precise conversion. When the input frequency waveform has a negative going transition, pin no.6 is driven momentarily lower than 13V threshold voltage at pin no.7 (nominally biased 2V lower than the supply voltage).


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Frequency to Voltage ConverterFig. 4

When a signal change occurs, the LM331's input comparator sets an internal latch and initiates a timing cycle.

t = 1.1 * Rt * Ct ………… (1)

C1, the filter capacitor filters this pulsating current from pin 1. During the timing cycle a precision current source

i = (1.1V) / Rs ………… (3)

flows out of pin no.1 and charges C1 up to the voltage adjusted by Ct and Rt

i.e. output voltage at the end of the charging cycle C1 stops charging and allows it to discharge through RL (R1 on AB29 board). That is the reason why the output waveform is not exactly a constant dc level but a rippled voltage. The output Voltage can be calculated by equation,

Vout = Fin * RL * (1.9) * 1.1 * Rt * Ct (V) RS ……… (4)Two problems remain, however, the output includes about 13 mVp-p ripple, and it also lags 0.1 second behind an input frequency step change, settling to 0.1% of full-scale in about 0.6 second. This ripple and slow response represent an inherent tradeoff that applies to almost every F/V converter. The output ripple (p-p) is given by

Output Ripple (p-p) = (1.9) * 1.1 * Rt * Ct

C1 * RS ………. (5)

The output waveform of the F-V converter is as shown below


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Fig. 5

AB29 Board Interpretation

AB29 contains both the circuits of F-V converter and V-F converter on single board. It explains the detailed signal flow in the various blocks within the IC LM331 and associated circuit for a particular configuration. The front view of the board contains connecting sockets for connecting external components to IC LM331 for completing circuit for either F-V converter or V-F converter (connections are mentioned in experiments). You can compare the board layout with Fig.2 for understanding it completely.

Following designations are used on board

IC U1 : Input Comparator

IC U2 : Time Comparator

S1 : Current Switch

S2 : Reset Transistor (transistor acting as switch)

Integrator (for V-F Converter) : Op-amp integrator with input 100K resistance.

Voltage Divider Network : Combination of 10K and 68K resistance attached to pin no. 7 in fig. 1.

Vref : .A 10K resistance connected to ground to one end and to the other end it will be connected to pin no.6 of IC LM31 when configured as V-F Converter.


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Experiment 1

Objective : To study the operation of LM331 as Voltage to Frequency Converter.

Apparatus required :

1. Analog board AB29.

2. DC power supplies of +/-12V and a variable negative dc supply from external source or ST2612 Analog Lab.

3. Oscilloscope.

4. 2mm patch chords.Circuit diagram :

Circuit used to study the operation of LM331 as Voltage to Frequency Converter is shown below :

Fig. 6


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Procedure :

1. For developing V-F converter circuit make the following connections using patch chords on AB29 board to make the circuit as shown in fig.1 :

• Connect point b to point c (i.e. pin no.6 Input to U1 to Voltage Reference Vref). This will set pin no. 6 at a constant reference voltage.

• Connect the point q to point p (i.e pin no.7, Input of U1 to Integrator Output).

• Connect the point m to point n (i.e pin no.3 from O/P driver & Protection Circuit to R3).

• Connect the point To CtX to point to the timing capacitor Ct1.

• Connect the point d to point f (i.e pin no.1 from Current mirror & Band Gap Reference Circuit to Integrator Input).

2. Connect +12V and -12V DC power supplies at their indicated position on AB29 board from external source or ST2612 Analog Lab.

3. Keep the Gain Adj. Pot (P1) in middle position.

4. Apply the negative variable DC supply between points Vin (for V-F Converter) and gnd and start increasing its value in negative direction (0V, -100mV…….-12V).

5. Observe the output waveform between points Fout (pin no.3) and gnd on the oscilloscope. For a particular range of input signal the output wave will appear. Note the range of input voltage for which the output signal appears on oscilloscope.

6. Repeat the above steps (from 1 to 5) after changing Ct to different values (Ct1 and Ct3).

7. To cross-check the results obtained calculate the O/P voltage using equation 2.

Result :


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1. Note down (when To CtX is connected to Ct1):

(i) Higher value of voltage for which signal appears (Vin1) =……V

(ii) Lower value of voltage for which signal appears (Vin2) =………V

2. Calculated frequency at Vin1 = ………….. (Hz)

3. Calculated frequency at Vin2 = ………….. (Hz)

4. Round off both the frequencies (eg. Let the calculated value of frequency at Vin = -1V is 1.102KHz then round it off to 1KHz)

5. f1 (rounded value of frequency at Vin1) = …………….. (Hz)

6. f2 (rounded value of frequency at Vin2) = ……………..(Hz)

7. Keep the voltage at Vin1 and adjust the output frequency (Fout) to exactly f1 value using pot. P1 (Gain Adj. Pot)

8. Keep the voltage at Vin2 and adjust the output frequency (Fout) to exactly f2 value using pot. P1 (Gain Adj. Pot)

9. Repeat the steps 7 and 8 at least twice or thrice to exactly calibrate the frequency w.r.t. input voltage.

10. Calculate and crosscheck the results using eq.2 by keeping the value of input voltage Vin as Vin1 and then Vin2.

11. Repeat the procedure when CtX is connected to Ct2 and then to Ct3.


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Experiment 2 Objective : To study the operation of LM331 as Frequency to Voltage Converter.

Apparatus required :

1. Analog board AB29.

2. DC power supplies of +12V and -12V from external source or ST2612 Analog Lab.

3. Function Generator.

4. Oscilloscope.

5. Voltmeter.

6. 2mm patch chords.Circuit diagram :Circuit used to study the operation of LM331 as Frequency to Voltage Converter is shown below :

Fig. 7


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Procedure :

1. For developing F-V converter circuit make the following connections using patch chords on AB29 board to make the circuit as shown in fig.4

• Connect the point a to point b (i.e pin no. 6, input of comparator IC U1 to Cin).

• Connect the point q to point r (i.e pin no.7, input of comparator IC U1 to Voltage divider network).

• Connect the point n to gnd (i.e pin no. 3, Output of Output driver & protection Circuit to gnd).

• Connect point d to point e (i.e. pin no 1 to filter circuit)

• Connect the point To CtX to point Ct1 (Timing Capacitor).

2. Connect supply of +12V and -12V DC at their indicated position on AB29 board from external source or ST2612 Analog Lab.

3. Keep the Gain Adj. Pot (P1) in middle position.

4. Apply a 10Vp-p Square wave signal between points Fin and gnd and start increasing its frequency from 100Hz.

5. Observe the output voltage on multi-meter between points Vout and gnd. Note down the range of frequency for which the output voltage is increasing linearly.

Note : After and before the limiting frequency the output voltage will either become zero or start decreasing. These values are beyond the range of conversion.

6. You can also observe the output voltage ripple on oscilloscope.

7. Repeat the above steps (from 1 to 6) after changing Ct to different values (Ct1 and Ct3).

8. To cross-check the results obtained, calculate the O/P voltage using equation 4.


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Result :

1. Note down (when To CtX is connected to Ct1):

(i) Lower value of frequency for which output dc signal is in linear range (Fin1) =……….Hz

(ii) Lower value of frequency for which output dc signal is in linear range (Fin1) =……….Hz

2. DC voltage at Fin1 = ………………………. (V)

3. DC Voltage at Fin2 = ……………………… (V)

4. Round off both the voltages (eg. Let the calculated value of voltage at 1KHz is 1.07V then round it off to 1V)

5. V1 (rounded value of voltage at Fin1) = …………….. (V)

6. V2 (rounded value of voltage at Fin2) = …………….. (V)

7. Keep the frequency at Fin1 and adjust the output voltage (Vout) to exactly V1 value using pot. P1 (Gain Adj. Pot)

8. Keep the frequency at Fin2 and adjust the output voltage (Vout) to exactly V2 value using pot. P1 (Gain Adj. Pot)

9. Repeat the steps 7 and 8 at least twice or thrice to exactly calibrate the frequency w.r.t. input voltage.

10. Calculate and crosscheck the results using eq.4 by keeping the value of input frequency Fin as Fin1 and then Fin2.

11. Repeat the procedure when CtX is connected to Ct2 and then to Ct3.


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Datasheet


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AB29

Warranty

1) We guarantee the instrument against all manufacturing defects during 24 months from the date of sale by us or through our dealers.

2) The guarantee covers manufacturing defects in respect of indigenous components and material limited to the warranty extended to us by the original manufacturer, and defect will be rectified as far as lies within our control.

3) The guarantee will become INVALID.a) If the instrument is not operated as per instruction given in the

instruction manual. b) If the agreed payment terms and other conditions of sale are not

followed.c) If the customer resells the instrument to another party.d) Provided no attempt have been made to service and modify the

instrument.

4) The non-working of the instrument is to be communicated to us immediately giving full details of the complaints and defects noticed specifically mentioning the type and sr. no. of the instrument, date of purchase etc.

5) The repair work will be carried out, provided the instrument is dispatched securely packed and insured with the railways. To and fro charges will be to the account of the customer.

DESPATCH PROCEDURE FOR SERVICE

Should it become necessary to send back the instrument to factory please observe the following procedure:

1) Before dispatching the instrument please write to us giving full details of the fault noticed.

2) After receipt of your letter our repairs dept. will advise you whether it is necessary to send the instrument back to us for repairs or the adjustment is possible in your premises.

Dispatch the instrument (only on the receipt of our advice) securely packed in original packing duly insured and freight paid along with accessories and a copy of the details noticed to us at our factory address.


AB29

List of Service Centers

1. Scientech Technologies Pvt. Ltd.90, Electronic Complex Ph : (0731) 2570301Pardesipura, Email : [email protected] INDORE – 452010

2. Scientech Technologies Pvt. Ltd.First Floor, C-19, Ph : (011) 22157370, 22157371F.I.E., Patparganj Industrial Area, Fax : (011) 22157369DELHI – 110092 Email : [email protected]

3. Scientech Technologies Pvt. Ltd.New no.2, Old no.10, 4th street Ph : (044) 42187548, 42187549

Venkateswara nagar, Adyar Fax : (044) 42187549CHENNAI – 600025 Email : [email protected]

4. Scientech Technologies Pvt. Ltd. 202/19, 4th main street Ph : (080) 51285011 Ganganagar, Fax : (080) 51285022 BANGALORE- 560032 Email : [email protected]. Scientech Technologies Pvt. Ltd.

8,1st floor, 123-Hariram Mansion, Ph : (022) 56299457 Dada Saheb Phalke road, Fax : (022) 24168767 Dadar (East), Email : [email protected] MUMBAI –400014 6. Scientech Technologies Pvt. Ltd. 988, Sadashiv Peth, Ph : (020) 24461673 Gyan Prabodhini Lane, Fax : (020) 24482403 PUNE – 411030 Email : [email protected]. Scientech Technologies Pvt. Ltd SPS Apartment, 1st Floor Ph : +913355266800 2, Ahmed Mamoji Street, Email : [email protected]

Behind Jaiswal Hospital, Liluah, HOWRAH-711204 W.B.8. Scientech Technologies Pvt. Ltd Flat No. 205, 2nd Floor, Ph : (040) 55465643 Lakshminarayana Apartments Email : [email protected] ‘C’ wing, Street No. 17, Himaytnagar,


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HYDERABAD- 500029List of Accessories

1. 2mm patch cord (Red)………………………………………..2 Nos.

2. 2mm patch cord (Blue)………………….……………………5 Nos.

3. 2mm patch cord (Black)……………………………………...4 Nos.


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Notes


AB29

Notes


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Notes


Documents

AB29 F-V and V-F Converter Analog Lab Ver. 1.0 QUALITY · PDF fileF-V and V-F Converter Analog Lab Ver. 1.0 ... When a signal change occurs, the LM331's input comparator sets an internal