 Hello and welcome to the video lecture on input and output devices. At the end of this session, students will be able to apply CAD fundamentals as well as advanced manufacturing technology to industry problems. The following topics will be discussed in this video lecture. Input devices, output devices, input devices. So what are actually input devices? So whenever we work with a computer, we need to enter data. Data may be any information and instructions to the computer using some devices. These devices are called input devices. These devices convert data and instructions to a form that can be recognized by the computer. So let's discuss some of the input devices, keyboard. It's the most commonly used input device. It allows data entry into a computer system by pressing a set of keys which are neatly mounted on a keyboard. It contains some extra command keys and function keys that affect the operation of computer or the keyboard itself. There may be various types of keyboard like a standard keyboard or multimedia keyboard or wireless keyboard. So what are the applications with respect to the CADCAM system? It may be used in the graphics like used to provide the screen coordinates, menu selection, gaming controls and for entering many graphics function. The second input device is the mouse. The basic principle on which a mouse works is that you have a ball and under the ball we have XY transducers which are fixed. So these are basically let's say X and Y variable resistors. As a result of this, if you move the mouse in X direction, the resistance of the X variable resistor will change. If you move it in the Y direction, the resistance of the variable resistor in the Y variable will change and the resistance is taken as the measure of the position of the mouse. Now let us discuss the third input device that is the tracker ball. You can find the tracker ball. The tracker ball is a ball which is there almost next to the keyboard. And you can change the orientation of the ball which changes the position of cursor on the screen joystick. I move the stick in either direction. The resistors fixed at the bottom, the resistance changes and their position can be seen on the screen. Now the fifth input device that is light pen. In a light pen, you have a light sensitive diode which is used to point onto the screen. From this pen, we can pick items from the menu. We can directly point your item on the menu and click that. Normally, if you have a mouse, you are moving the mouse on the pad or on a board. In this, you don't have to do that. In this, you just take the pen and point it on the screen and click it there. This basically works on a principle of sensing the light signal over there and current position of the screen is then sent back to the computer or to the CPU. The way it works is let's say we will be talking of raster graphics devices. In raster graphics devices, there is an electron gun which starts from one corner and spans the full screen like this at the rate of about 40 times a second or 50 times a second. It will be spanning the full screen which means the gun starts from one corner and goes to the right. Come back to the left corner again goes to the right. So the moment the light pen senses the light over here, it knows how much time lag is there between starting point and this point. And that time lag is used to compute the total distance traveled and hence the position of light pen at that point. This is how the position of the light pen is sensed and fed back to the machine. This is the basic principle of the light pen. Now pause this video for a few seconds and try to write answer to the following question. What is a light pen? Is it a mechanical input device, optical input device, electronic input device or optical output device? I think probably you have wrote the answer to the following question. Output device as the word say output. Output devices are the devices to show output to the reuser. You may have heard about example like printer which is showing the hard copy or it may be your monitor. So these are the output devices. So let us today discuss about the plotter as the output devices. A plotter is a printer designed for printing vector graphics. Instead of printing individual dots on the paper plotters draw continuous lines. This makes plotters ideal for printing architectural blueprints, engineering designs and other CAD drawings. So we will be discussing today about two types of plotter that is flatbread plotter and drum plotter. Flatbread plotter. In a flatbread plotter we have a table on which sheet of paper is fixed. Now on this sheet of paper we will be having the pens, set of pens. You can see the pens are mounted on the corner. The pens can move in the x and y direction. So the pens will be mounted on a carriage and they can move in x and y direction. The paper is fixed. So if you want to make a drawing of a A4 size we will take a paper of A4 size, fix it on this plotter and the pens will move in the x and y direction. For moving the pens in the x direction we have a x drive motor. And for moving the pens in the y direction we will have a y drive motor and as the pen is moving we need a mechanism to either lower the pen for drawing it or to raise it so that no line is drawn during the motion. So we have a pen raise and lower mechanism. So in this case essentially a paper is fixed onto the table and the paper can move in the x and y direction. So let us discuss the second type plotter called drum plotter. In the case of a drum plotter we have a drum. On this drum the paper is fixed. The paper can hang on both the sides and the paper is fixed on this. The drum can rotate by the rotation of the drum we get the motion in the y direction and the pens can move in this direction. So x direction motion. So the x direction motion is given by let's say an x drive motor and the y direction motion is given by the drum motor and of course we have a mechanism to raise and lower the pen. The basic advantage of this drum plotter is it takes less space and the total moment of the pen is much less. And typically these plotters are faster. The disadvantage is high cost and high cost of maintenance. Following are the references. Thank you.