Servo Motors and PWM

While playing with servo motors, I came across an interesting concept of pulse width modulation connected to the servo motors which I will be discussing here.

Servo library has to be called and an object has to be made in the Arduino IDE for controlling the servo motor. Once we do that we use object_name.write() and specify the angle which the servo should be turned to. Servo control is actually achieved by sending a PWM signal to the servo motor. But since there are only 6 PWM pins on the Arduino Uno does that mean we can connect only 6 servos to it ?

For comparison I used the same servo on both PWM as well as non-PWM pins on the Arduino and there was no visible performance difference ! If PWM is used by servos, there has to be a difference ! So whats the hack then ?

The key to this is the fact that the Servo library does not use PWM !! The servo pulses are 1ms long. Therefore they must be driven by the frequencies around 1 kHz which is very easy to generate by the software. When we call the write() function, it computes a pulse width in micro seconds and stores it in a global array. Then there is a single timer that regularly triggers an interrupt which changes the output signals according to each channel`s desired pulse width. Hence, the Servo library uses standard means to change the state of the pins just as we do Bit-Banging !

The Servo library supports up to 12 servos on most of the Arduino boards using only one timer. It can actually run servos on all pins simultaneously !

Author : Yug Ajmera (2017 Batch)

Rapid Diagnostic Tests

Common Principle of all the rapid diagnostic tests:

Currently available Rapid Diagnostic Tests comprise of a base membrane such as nitrocellulose. A detector reagent (antigen/antibody–indicator complex) specific to the analyte, impregnated at one end of the membrane. A capture reagent is coated on the membrane at the test region.

When the specimen is added to the sample pad, it rapidly flows through the conjugate pad. Analyte, if present in the specimen, binds to the detector reagent. As the specimen passes over the test band to which the capture reagent is coated, the analyte-detector reagent complex is immobilized. A colored band proportional to the amount of analyte present in the sample, develops. The excess unbound detector reagent moves further up the membrane and is immobilized at the control band.

For the past ten years, the number of dengue cases has gradually increased in India. According to the statistics, India in 2017 has seen 11,832 more cases of dengue compared with 2016. As healthcare facilities in many dengue endemic regions lack laboratory support, early dengue diagnosis must rely on either clinical recognition or a bedside diagnostic test.

Dengue fever is a severe, flu-like illness that affects infants, young children and adults, but seldom causes death. It is transmitted by the bite of a mosquito infected with one of the four dengue virus serotypes.

The immune response to this virus includes the production of IgM antibodies by the 5th day of symptoms, which remain in the circulatory system for 30-60 days. IgG antibodies appear by the 14th day of infection and persist for life. A secondary infection often results in high fever and, in many cases, initiates hemorrhagic events and circulatory failure. A secondary infection also induces an IgM antibody response after 20 days of infection and IgG antibodies rise within 1-2 days after the onset of symptoms.

Therefore, patients with secondary infections will have a positive IgG result, usually with a positive IgM result as well.

Thus, the use of a reliable and sensitive rapid serological test that can simultaneously detect the presence of anti-dengue IgG and IgM antibodies is of great clinical utility. The DenguCheck provides an excellent methodology for specifically detecting anti-dengue IgG and IgM antibodies. The presence of high titers of IgG antibodies on the Dengue rapid test does not interfere with the detection of IgM antibodies in the sample. By using a mixture of highly purified dengue proteins, the Dengue rapid test is able to detect all 4 Dengue serotypes.

This Dengue Rapid Test is a new generation immunochromatographic test using recombinant dengue viral antigens of all four serotypes to detect specific antibody response. Serum, plasma or whole blood samples may be used with this

This summer, I had the opportunity to intern at Zephyr Biomedicals, Goa where I received the thorough understanding of the company’s product “DenguCheck – Rapid Diagnostics Test for Dengue” and had to come up with effective measures that, would aid the laboratory personnel minimize erroneous reporting and troubleshoot confidently for confident result reporting.

Author : Mahima Varwandkar (2016  batch)

Embedded Systems

Has the phrase ”Embedded systems” ever intrigued you in the recent times? Well, not to oversimplify it but embedded systems are nothing but a purpose specific combination of hardware or software, usually parts of larger electronic or mechanical systems. Ninety-eight percent of all microprocessors are manufactured as components of embedded systems. Vending machines, toys, electronic appliances are all common targets of embedded systems. So, it’s no stranger to you at all. Now, there may exist multiple embedded systems for industrial applications and real time processing. Bus architecture (framework of wires) is a means of data exchange for these systems. Let us look at one such architecture.

As the name suggests a sensor ‘senses’ changes in parameters such as temperature or humidity or any other variable from the field environment and sends the data but what happens after? This data is manipulated to check for appropriate levels and for further monitoring.

And how to manipulate this data? Using different data processing systems of course. One of the major systems being the Versa Modular Europa (VME) systems. VME is a multi-processor bus-based system which consists of a bin consisting of 21 slots and cards with individual specifications that fit into these slots. How exactly does this work, you ask? Well, the bin supports a common bus and so any card inserted into the bin shares the bus with other cards in the bin. So, I can decide to share the data, received and stored in an Analog Input Card with the CPU card and wait, maybe its neighbor too. Analog Output Card, Digital Input card, Resistor Output Card are among the various cards which the VME system supports.

This summer, I got to work on the development of a hardware interface library for an Analog Input Card in a VME based embedded system at IGCAR, Kalpakkam.

Although there is no undergraduate course on this, Dr. Syed Ershad Ahmed is handling the higher degree course, Embedded System Design ( EEE G512). 

Author:- Amogh B S , 2016 batch

 

Nanoscience

An important aspect of Nanoscience is understanding how matter in the nanoscale interacts with electromagnetic radiation. A thorough understanding of this interaction will help us develop better sensors, nanoantennas, nanophotonic circuits and can even offer a better solution to treating cancer.

At the forefront of this aspect is the field of Plasmonics. Plasmonics explores how electromagnetic field can be confined and guided in dimensions smaller than the wavelength of light. Many interesting phenomena arise out of this interaction of light with plasmonic nanoparticles which in turn have a plethora of applications. A few of them are:

• Plasmonic Heating: Using light to heat nanoparticles. This field is being explored as a method to destroy cancerous tumours without damaging healthy tissue.
• EOT or Extraordinary Optical Transmission. This has great applications in Photonic circuits.
• Surface Plasmon Resonance: This involves electrons resonating with the driving electromagnetic field. This has applications in various bio sensors.

Prof. Kannan Ramaswamy of the Physics department is one of the active researchers in this field from our campus.

This summer I had an internship in CeNSE, IISc where I had to build an automated stage for a microscope which will be used to study plasmonic nanoparticles and other various aspects of how light interacts with matter in the nanoscale.

Author:- Nikhil Navaratna, 2015 batch