Analog Experiments Anywhere

by ajoyraman in Circuits > Electronics

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Analog Experiments Anywhere

ASLK_SigGen_Scope.jpg
Two DIY micro-controller based USB connected electronic units which along with the Texas Instruments Analog System Lab Starter kit and a laptop permit you to conduct analog experiments anywhere.

It would be wonderful  if senior students and laboratory supervisors built these units so that they could be used in their laboratories by freshers.




Aj-SigGen-PS     http://ajoyraman.in/DDS_SigGen_PS.html

Aj-Simple-Scope      http://ajoyraman.in/USB_Simple_Oscilloscope.html

Analog System Lab Starter Kit ASLKv2010    http://www.uniti.in/teaching-material/analog-system-lab-starter-kit

Aj-SigGen-PS

Aj-SigGen-PS.png
This unit is designed to compliment the Aj-Simple-Scope and serve as a teaching aid for budding engineers, electronic enthusiasts and hobbyists.

This USB connected unit implements a microcontroller based DDS Signal Generator providing Sin and Triangular waveforms with adjustable magnitude and offset up to 50 kHz. TTL and 1 V square waves are simultaneously provided. Additionally ± 12V and a variable +2 to 7V output with a total capacity of  1W is provided to power external circuits under test.


Block Schematic and Function Description of Signal Generator and Power Supply Unit

Aj-SigGen-Block-Diagram.png
 For ease of portability the unit is powered and controlled from the USB port of a PC.


Two PIC18F14K50 microcontrollers are used to provide the functionality of the unit.

The first PIC microcontroller implements the following functions:

• Communicates with the host PC for enumeration as a USB to UART device

• Sets up the unit as a 500mA device

• Switches on power to the DC-DC converter

• Provides the complimentary square wave drive to the DC-DC converter

• Acts as a USB communication interface to the second PIC

• Provides the Amplitude reference for DAC2

• Provides the digital word for DAC1 giving the offset value.


The second PIC microcontroller implements the remaining DDS functions

• Direct Digital Synthesis (DDS) signal generation

• Sin/ triangle word output to DAC2

• TTL and 1 V square reference output


The DC-DC converter is a driven 1W, 5V to ± 12V operating at 100 kHz. The +12 V output is fed to a linear regulator to provide a variable +2 to 7 V output controlled by a variable potentiometer.

The DC-DC converter provides full protection to the host PC USB port as its outputs are short circuit and current limit protected.

The circuit under test can be rigged up on a standard breadboard and powered from the power sockets provided.

Aj-Simple-Scope

Aj_Scope_Main.jpg
This unit is designed to compliment the Aj-SigGen-PS and serve as a teaching aid for budding engineers, electronic enthusiasts and hobbyists.

This USB connected unit implements a microcontroller based 2-Channel Oscilloscope providing continuous sampling rates up to 100 ksps and 20 Msps using equivalent time sampling. Common DSO features such as spectrum analysis, waveform capture and data saving are provided. The input range is ± 12V with additional gain settings of X2 and X5. Trigger and sweep options are also provided.

Block Schematic and Function Description of the Simple-Scope Unit

Aj-Smple-Scope.png
For ease of portability the unit is powered and controlled from the USB port of a PC.


A PIC18F14K50 and dsPIC30F4011 microcontrollers are used to provide the functionality of the unit.

The first PIC microcontroller implements the following functions:

• Communicates with the host PC for enumeration as a USB to UART device

• Sets up the unit as a 200mA device

• Switches on power to the DC-DC converter

• Acts as a USB communication interface to the second PIC


The second PIC microcontroller implements the main Oscilloscope Functions

• Analog to Digital conversion of the CH1 and CH2 signal conditioned inputs at the required sampling rates

• Trigger interrupt handling

• Responding to serial commands from PIC1 and sending back the acquired data.

• A  Busy signal is  also generated


The dual-charge pump circuitry of the MAX232 is used as a DC-DC converter to provide a nominal ± 10V to all the analog circuitry.

Typical Test Results Using the ASLK

000_1.5.3 Slew rate of LM741 opamp inv gain 2.jpg
007_Fig 1.6 b Time Response of Negative Feedback Amplifiers.jpg
008_Fig 1.7 Transfer Characteristics Inv Amp Gain 2.2.jpg
009_Fig 1.7 Transfer Characteristics Non-iInv Amp Gain 3.2.jpg
018_Fig 1.10 DAC out for 16 Bit Count +5V Ref and Sin Wave Ref.jpg
002_Fig 2.1 Inv Comp With Hytterisis YT.jpg
001_Fig 2.1 Inv Comp With Hytterisis XY.jpg
003_Fig 2.3 Non-Inv Schmidt YT.jpg
002_Fig 2.3 Non-Inv Schmidt XY.jpg
004_Fig 2.4 Astable Multivibrator.jpg
005_Fig 2.4 DFT of Sq Op of Astable Multivibrator.jpg
006_Fig 3.4 a SqWave Input to Differentiator.jpg
007_Fig 3.4 b Triangular Input to Differentiator.jpg
023_Fig 3.4b Triagular wave to differentiator ( small fb capacitor added).jpg
010_Fig 3.4 b Integrator output for triangular wave.jpg
011_Fig 3.4 a Integrator output for square  wave.jpg
012_Fig 4.2 Output of Active filter gain=1, Q=10, f0=723Hz.jpg
019_Fig 6.1 VCO unmodulated.jpg
014_Fig 6.2a Function Generator.jpg
020_Fig 6.1 DFT of VCO output (unmodulated).jpg
013_Fig 6.2 b  FSK generator .jpg
022_Fig 6.1 VCO output (modulated).jpg
021_Fig 6.1 DFT of VCO output (modulated).jpg
016_Fig 9.1 DC-DC Converter Vi and Vc .jpg
017_Fig 9.1 DC-DC Converter V01 and Vc .jpg
015_Fig 8.4 AGC Circuit for  output voltage = 1 V peak.jpg
Refer to the Analog Systems Lab Manual from Texas Instruments

http://www.uniti.in/images/teaching-material/aslk-lab-manual-2edition.pdf

It is extremely easy to setup the analog experiments in the lab manual on the kit and test them using the Aj-SigGen-PS and Aj-Simple-Scope units.

The kit is powered from the Aj-SigGen-PS which also provides test signal inputs as required. The wave-forms at selected test points on the circuits are captured using the Aj-Simple-Scope and saved as image files on the laptop.

Typical wave-forms which have been captured are shown.

These demonstrate the capabilities of the ASLK and how to test the circuits using the two DIY units presented here.

For further details of the Hardware and freely downloadable Software kindly visit http://www.ajoyraman.in