Hartley Oscillator


Aim:


To study the operation of Hartley Oscillator

Apparatus:


1.     Analog board AB68
2.   DC Power Supplies +12V from external source or ST2612 analog lab
3.   Oscilloscope 20 MHz, Caddo 802 or equivalent
4.   2 mm patch cords

Theory:


The Hartley oscillator is one of the simplest and best known oscillators and is used extensively in circuits, which work at radio frequencies.  The transistor  is in voltage divider bias which sets up Q-point of the circuit. The output voltage is fed back to the base and sustains oscillations developed across the tank circuit, provided there is enough voltage gain at the oscillation frequency. The resonant frequency of the Colpitt oscillator can be calculated from the tank circuit used. We can calculate the approximately resonant frequency as
1

ResonantFrequency(fr) =

2πLT C

Here, the Inductor used is the equivalent Inductance. In Hartley oscillator the circulating current passes through the series combination of L1 and L2. Therefore equivalent Inductance is,

LT = L1 + L2 + 2M
 
Where, M is the mutual inductance between two inductors.


M = K    L1L2
Where, K is the coefficient of coupling, lies between 0 to 1. The coefficient of coupling gives the extent to which two inductors are couple.

Circuit Diagram:



Procedure:

1.     Connect +12V dc power supplies at their indicated position from external source or ST2612 Analog Lab.
2.   Connect a patch cord between points a and b and another patch cord between point d and ground.
3.   Switch ON the power supply.
4.   Connect oscilloscope between Vout and ground on AB68 board.
5.   Record the value of output frequency on oscilloscope.
6.   Calculate the resonant frequency using equation mentioned.
7.    Compare measured frequency with the theoretically calculated value.
8.   Switch off the supply.
9.   Remove the patch chord connected between points a and b and connect it between points a and c.

10.   Remove the patch cord connected between points d and ground and con- nect it between point e and ground.
11.     Follow the procedure from point 4 to 7.

Result:

    When patch cords are connected across a and b.
Practically calculated Output frequency (on CRO): 1.055 MHz Theoretically calculated values:
LT : 2.078 x 105 H
Resonant frequency (fr): 1.1038 MHz

    When patch cords are connected across a and c
Practically calculated Output frequency (on CRO): 310.6 KHz Theoretically calculated values:
LT : 2.278 x 104 H
Resonant frequency (fr): 334 KHz

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Colpitt’s Oscillator


Aim:

To study the operation of Colpitt’s Oscillator

Apparatus:


1.     Analog board AB67
2.   DC Power Supplies +12V from external source or ST2612 analog lab
3.   Oscilloscope 20 MHz, Caddo 802 or equivalent
4.   2 mm patch cords

Theory:


Oscillators are circuits that produce specific, periodic waveforms such as square, triangular, sawtooth, and sinusoidal. Two requirements for oscillation are:

1. The magnitude of the loop gain AvB must be at least 1, and
2.            The total phase shift of the loop gain AvB must be equal to 0o or 360o.  If  the amplifier causes a phase shift of 180o, the feedback circuit must provide an additional phase shift of 180o so that the total phase shift around the loop is 360o.

The Colpitt oscillator is  one of  the  simplest and best known oscillators and  is used extensively in circuits, which work at radio frequencies. The transistor is in voltage divider bias which sets up Q-point of the circuit.In the circuit note that Vout is actually the ac voltage across C2. This voltage is fed back to the base and sustains oscillations developed across the tank circuit, provided there is enough voltage gain at the oscillation frequency.

The resonant frequency of the Colpitt oscillator can be calculated from the tank circuit used. We can calculate the approximately resonant frequency as
1

ResonantFrequency(fr) =

2πLC

Here, the capacitance used is the equivalent capacitance the circulating cur- rent passes through. In Colpitt oscillator the circulating current passes through the series combination of C1 and C2. Therefore equivalent capacitance is,


C equivalent) =   C1C2
(                                         C1 + C2




Procedure:

1.     Connect +12V DC power supplies at their indicated position from external source or ST-2612 Analog Lab.
2.   Connect a patch cord between points a and b and another patch chord between points d and g1.
3.   Switch ON the power supply.
4.   Connect oscilloscope between points f and g2 on AB–67 board.
5.   Record the value of output frequency on oscilloscope.
6.   Calculate the resonant frequency using equation mentioned.

7.    Compare measured frequency with the theoretically calculated value.
8.   Switch off the supply.
9.   Remove the patch chord connected between points a and b and connect it between points a and c.
10.   Remove the patch chord connected between points d and g1 and connect it between points e and g2.
11.     Follow the procedure from point 4 to 8.
12.   Connect +5V supply instead of +12V supply ly and follow the procedure from point 2 to point 11.

Result:

    When patch cords are connected across C1 and C2
Practically calculated Output frequency (on CRO): 1.073 MHz Theoretically calculated values
Cequ: 14.98 nF
Resonant frequency (fr): 1.18  MHz Output voltage amplitude : 1.90 V (Vp-p)


    When patch cords are connected across C3 and C4
Practically calculated Output frequency (on CRO): 1.76 MHz Theoretically calculated values
Cequ: 4.71 nF
Resonant frequency (fr): 2.12  MHz Output voltage amplitude : 3.58 V (Vp-p)





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Essay Writing compition by Department of Atomic energy ( DAE )

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NASA MASS MISSION




Engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, have installed the SuperCam Mast Unit onto the Mars 2020 rover. The instrument's camera, laser and spectrometers can identify the chemical and mineral makeup of targets as small as a pencil point from a distance of more than 20 feet (6 meters).
SuperCam is a next-generation version of the ChemCam instrument operating on NASA's Curiosity Mars rover. It has been developed jointly in the U.S., France and Spain. Once France delivered the last piece of flight hardware, the instrument was fully integrated on the Mars 2020 rover on June 25, 2019, in the Spacecraft Assembly Facility's High Bay 1 clean room at JPL.
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Also to be installed in the next few weeks is Mars 2020's Sample Caching System, which includes 17 separate motors and will collect samples of Martian rock and soil that will be left on the surface of Mars for return to Earth by a future mission.
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SuperCam is led by Los Alamos National Laboratory in New Mexico, where the instrument's Body Unit was developed. That part of the instrument was installed in the body of the rover in May and includes several spectrometers, control electronics and software. The Mast Unit was built with contributions from numerous academic laboratories in France, led by the French space agency Centre National d'Études Spatiales, and includes the high-powered laser, a telescope, a camera, an infrared spectrometer and a microphone. Calibration targets on the rover deck are provided by Spain's University of Valladolid.
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News Media Contact
Andrew Good
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-2433
andrew.c.good@jpl.nasa.gov
Alana Johnson
NASA Headquarters, Washington
202-358-1501
alana.r.johnson@nasa.gov
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