Archive for July, 2008

FOSS in Engineering Colleges

July 21st, 2008 1 comment

Shayam has written a nice letter to his HOD on usage of free software in laboratory experiments. As a teacher, I am trying to use free software in my own college. The problems mentioned in his letter is existing in all most all colleges in Kerala.
The root cause for this is in the syllabus itself , rather the way in which syllabus is set. Let us look at CUSAT syllabus for Electronics and communication. ( Sorry, I can’t find it on the Cusat website. I have placed the 2006 Btech Scheme and syllabus for Electronics and communication here.).

See the 5th semester microprocessor laboratory.

PART II – 7 Lab sessions
1. Introduction to IBM/PC and its DEBUG program commands
– Examining and modifying the contents of the memory
– Assembling 8086 instructions with the ASSEMBLER commands
– Executing 8086 instructions and programs with the Trace and GO Command.
– Debugging a program
2. Assembly language program development using IBM/PC Macro assembler
– Creating an Assembler source file
– Assembling source program with MASM
– The link program – creating a RUN module
– Typical programming examples.

The DOS debug and masm are embedded in the syllabus itself.

Similarly look at Signal Processing Laboratory. 7th Semester

1. Familiarization of Signal processing tool box-MATLAB
2. Familiarization of DSP trainer kit (Sampling & reconstruction of signals)

List of experiments to be implemented

Generation of basic input signals ( both discrete & continuous)
DFT and spectral analysis computation of DFT, properties of DFT
Digital filter design- FIR & IIR Filters
Spectral estimation
Matlab is specifically mentioned even though all the above can be done in Octave or Scilab. I don’t know why it was not mentioned.
When we had a university inspection some time back , the inspection committee specifically asked for the Matlab license.

The syllabus revision committee generally consist of senior faculty mem4bers. Most of them are included in the committee on political lines on on merit. Kerala may be the only place in the world where you will find things like Turbo C , debug etc are taught to engineering graduates.

Categories: Engineering Education Tags:

Building Bitx part 2- The crystal filter.

July 15th, 2008 Comments off

The 10 MHz crystal filter is one of the most important modules of bitx transceiver. Bitx uses an IF of 10 MHz. 10 MHz crystal filters are available at approximately Rs10 ( 1 US$ = Rs40 approximately) in the Indian market. I bought 10 crystals from a local electronics shop. The first thing I did was to number the crystals with a marker pen.


I wired up the following circuit (as described in Farhan’s website.

I didn’t have 680pf in my junk box I used 560pf capacitor. The circuit was built on a small PCB as shown below.


The Test Circuit


The crystal test circuit wired in ugly style

Then I measured the frequency of the oscillator. My readings are tabulated below.

Crystal no Frequency in MHz
before closing the
Frequency in MHz after closing the switch
a 9.99531 9.99819
b 9.99535 9.99809
c 9.99553 9.99832
d 9.99560 9.99835
e 9.99547 9.99818
f 9.99558 9.99809
g 9.99530 9.99810
h 9.99560 9.99824
i 9.99567 9.99827
j 9.99587 9.99814
k 9.99582 9.99815

As per Farhans advice I choose 4 crystals that are matched.

Then I built the filter as shown below.


The filter half built.


10mhz filter completed.


10 MHz filter fixed to a small PCB for testing.

I have the following test set up in my shack.

a) a frequency counter. ( A beautiful piece of equipment I bought form vu2ptr during ham Fest.)

b) A DDS vfo

c) An oscilloscope.


My Test Setup

I terminated both sides of the filter with 200 ohm resistors and then the DDS out put was fed to the filter. The DDS frequency was varied and the filter output observed on the CRO. I have taken readings at 100 Hz apart. I plan to plot a curve using gnuplot tomorrow.

PIC 16F877 prototyping board – part 2

July 15th, 2008 Comments off

A low cost PIC 16F877 prototyping board is being developed at College of engineering Attingal under my guidance. The credit for develoment goes to Shibu and Manoj. The board is intended for classroom use. The idea is to provide a low cost platform for experimenting with PIC micro controllers. The proposed board will have easily attachable daughter boards for connecting various accessories such as key board, LEDs , switches etc. The board will be programmable via serial port through an ICSP programmer.

The first draft schematic of the board is give below. This board contains a PIC 16F877 and ICSP programmer interface. All ports of the PIC are available via FRC connectors.


The PCB pattern along with component lay out for building the board is shown below.


You can download a PCB pattern suitable for homebrewing can be found here.

We have just completed the first board and pictures of the same are provided below.

pic_prototype_board pic_protype_board1