Interfacing dataTaker

Ever wondered how remote controlling of a large number of instruments work in a given scenario of a big experimental set up such as superconductivity testing or missile launching where a large number of devices need to be handled simultaneously, with very less supply dedicated for it? Standardized protocol and data formats to log data play a very crucial role in addressing these scenarios. One of the pioneer tool in this field is dataTaker. 

-project and article contributed by Adil Wankhede, VNIT, Nagpur. 

Rubber bands- they can be stretched by our hands. Ever wondered how other materials such iron, copper, superconductors etc. could be stretched? A universal testing machine (UTM), also known as a universal tester, materials testing machine or materials test frame, is used to test the tensile strength and compressive strength of materials. The "universal" part of the name reflects that it can perform many standard tensile and compression tests on materials, components, and structures.

-project and article contributed by Shantanu Bhosale, EEE, VNIT, Nagpur.

Electricity is the present era’s OXYGEN. How restless we grow when there is a power cut in summer nights especially when we are about to go to bed, or having our dinner, watching TV or having exam the next day! Well these have become a matter of past as INVERTERS have protruded the whole market. Although last institutes, hospital and other large load rely on DG set, inverters have captured almost every home.

Won’t it be interesting to begin designing our own inverter? So let’s get started!!

Working of Analog Clock

Importance of time keeping is recognized ever since the life came into existence. From just days and nights demarcating the time to using sundials for time keeping in the days in medieval period to balanced wheels and pendulum clocks in 15 and 16^th century, time keeping had always remained a challenge to the scientists.

  

The first electric clock was patented in 1840 and since then there has been a lot of advancement in this sphere. Digital Clocks have capture the 21^st century world however analog clocks still remains a part of almost all the houses.

This post is dedicated to explaining the working of these analog clocks.

  

Relays are electrically operated switches. They have an electromagnet which controls the switching operation. Relays find uses in stabilizers, mechanical bots for switching action.

Now let us come to the working of the relays.

Relays as you can see has 5 terminals – Three on one and two on other. Two of the three terminals (those at the end) are connected to the electromagnet (coil’s terminals). The third one at the centre is the common (COM) and the two terminals on the other end are Normally Close (NC) terminal and Normally Open (NO) terminal. The metal part over the electromagnet is the armature .It’s one end is connected to the COM and the protruding end of it is the contact which switches between NO and NC terminal.

Normally Closed is the terminal to which the contact is resting when the electromagnet is not energized. NO remains open at that moment and hence its name.

When small DC voltage (12V in this relay) is applied across the electromagnet, the electromagnet get magnetised and the contact moves from NC to NO. As the source is withdrawn from the electromagnet, the contact returns back to NO position either by action of Spring or metal of suitable elasticity . The switching action takes around 30ms. Thus it allows us to switch between two states be it ON/OFF or left/right movement of motor or any other relevant condition. The appliances are connected at the NO, NC and the COM terminal.



These can be AC appliances or DC appliances depends upon the voltage and current rating of the relay.

Now the very important thing is how shall we determine which one is NO and which one is NC? It is very easy if you have a multimeter. Just put it to buzzer mode and check for conductivity with one end at the COM terminal and other on either of the 2 terminals without applying voltage to the electromagnet. Whichever terminal gives the buzzing sound is the NC. Even if you don’t have a multimeter, we can determine the terminals using a bulb and a cell and small wires. Just connect one end of the bulb to the COM and the other to any one end of the cell. Using small wire connect the other end of the cell to either of the terminals. The terminal for which the light glows is NC terminal.

Adaptors are devices which convert the AC supply to DC low voltage suitable for the devices. Few of the devices were we require adaptors are the video games, small DC motors, etc. It is very interesting to find what is actually inside an adaptor and how does it convert AC voltage (220v in India) to DC voltage in range of 0 -12v.

All the adapter have 3 important parts inside them:

• Step down Transformer: The step down transformer steps down AC voltage to a small value say 12v.


• Full Wave Rectifier: The full wave rectifier flips the negative portion of the sinusoidal secondary voltage to positive side. It has four diode connected in the fashion as shown in the circuit diagram. The input terminals are connected to the point 1 and 3 while the output is obtained from 2, 4. Rectifier uses the property of the diodes that they allow the flow of current through them only in one direction. When a positive cycle of current flows, the current leaves from D1 and return from D3. D2 and D4 do not allow the flow of current. When the negative cycle arrives then D2 and D4 are conducting and D3 and D1 become non-conducting. What we observe is that the current always leaves through point 2  and return from point 4 or we can say that 2 is always at higher potential than 4. This means that the current waveform for the negative cycles must have got reversed. The waveform we obtain in CRO confirms this.

• Capacitive Filter: The current waveform which we obtained is though unidirectional but sinusoidal in nature which is not proper for a DC application. To convert it close to an ideal DC we need to filter out it out. For thiswe generally use a capacitor of large value. Capacitor has a property of storing the energy (or we can say getting charged) when its terminal voltage is less than the supply voltage and getting discharge (or act as voltage source) when the source voltage drops below its terminal voltage. Let us understand this by studying the voltage waveform. In the rising side of the voltage waveform, the capacitor gets charged upto maximum voltage Vm. On the sloping down side, as the voltage becomes less than its terminal voltage, it expands its energy, thus preventing such a fast fall in the voltage. Voltage would have fallen by a very small amount by the time next cycle starts and it gets charged again. Thus we get an average voltage very close to DC voltage across its terminal.

 
Mouse is a pointing device which help us point at various objects on the desktop. It evolved from track ball. Earlier mouse had heavy spherical rubber ball and wheel with spokes aligned at 90 degrees which registers the rotation of the ball along x-axis and the y-axis to move the cursor on the screen.

The type of mouse we use these days is an optical mouse. Unlike rubber ball mouse, the optical mouse has a red led which is refracted to the ground (desk) through a prism. The light reflected back from the desk is captured by the light detecting chip (an imaging array of photodiodes) which detected movement of mouse relative to the desk and sends the signal in digital form through the data cable to the computer. The computer processes the data and makes the cursor moves accordingly. Detection of the movement of the mouse relative to the desk is through the Digital signal processor which manipulates the change in the pattern of sequence of image received by it.

Also we have scroll bar. The scroll bar is attached to a circular potentiometer but this potentiometer unlike other do not haul at the ends but allow rotation. The analog is converted to digital form and then sent to the computer through the data cable.

There are micro switches for left click right click and the scroll click.

The tube light has three important parts:

• 1.       Tube (containing 2 filaments + vapour +  mercury gas)


• 2.       Ballast


• 3.       Starter
•  

The tube light has the filaments connected in series with the starter and ballast. The current flows through the circuit while the ends of the bimetallic strips in the starter are in contact. This warms up the tungsten filament. It starts emitting electron. The alternating nature of the input current leads growing and shrinking of the voltage across the ballast. This induces voltage spikes across the filaments which helps in movement of ions from cathode to anode.