Printers.pptx
- 1. Printers Dr. Kinjal Patel Assistant Professor, Department of Physics, UTU, Bardoli
- 2. Classification of Printers Printers used in computers are classified in the following three broad categories. 1. Impact and Non-impact Printers Impact printers form characters on a paper by striking the paper with a print head and squeezing an inked ribbon between the print head and the paper. Non-impact printers form characters without engaging the print mechanism with the print surface, e.g. by heating sensitised paper or by spraying ink from a jet. 2. Fully Formed Character and Dot Matrix Printer Fully formed characters are like those made by a standard typewriter—all parts of characters are embossed in the reverse on the type bars of the typewriter. When printed, all type elements appear connected or fully formed. Dot matrix characters are shaped by combinations of dots that form a group representing a letter or number when viewed together. 3. Character at a Time and Line at a Time Printer Character at a time printers (character printers or serial printers), print each character serially, and virtually instantaneously Ref. Electronic Instrumentation by H S Kalsi
- 3. Printer Character Set Most printers used with mini or micro computers use ASCII codes. Printers are specified as using the 48 character set, the 64 character set, the 96 character set or the 128 character set. The 48 and 64 character sets include commonly used special symbols, numbers, a space, and upper case (capital) English alphabets. The 96 ASCII character set includes the lower case English alphabet and several additional special symbols. Of the 96 characters, ‘space’ and ‘delete’ do not print, leaving only 94 printable characters. The entire 128 character ASCII set contains 32 characters normally used for communication and control. These characters usually do not print, but correspond to expandable functions, such as communication and control. Ref. Electronic Instrumentation by H S Kalsi
- 4. Drum Wheel Ref. Electronic Instrumentation by H S Kalsi
- 5. Ref. Electronic Instrumentation by H S Kalsi Drum Wheel The typewriter is the classic example of this printer, with characters fully formed-because they are embossed on each type bar. The print mechanism is a vertical cylinder. Characters are embossed in several rows and columns around the cylinder, as shown in Fig. The ASCII character code sent to the printer, is translated into motion that rotates the cylinder, so that the column containing the desired character faces the paper. The cylinder is then raised or lowered (depending on the ASCII code) to present the column containing the desired character to be printed directly to the paper. A hanuner mechanism propels (hits) the cylinder towards the paper, Where only the positioned character strikes the ribbon, creating the printed impression of the character on the paper.
- 6. Ref. Electronic Instrumentation by H S Kalsi Daisy Wheel
- 7. It has characters mounted on the periphery of a spinning print head, known as a daisy wheel printer. and is shown in Fig. A daisy wheel print head is mounted on a rotating disk with flexible flower like petals similar to a daisy flower. Each petal contains the embossed character in reverse. As the daisy wheel spins, a hammer strikes the desired flexible petal containing the character, in turn impacting the paper with the embossed character through an inked ribbon. To print a letter, the wheel is rotated until the desired letter is in position over the paper. A solenoid driven hammer then hits the petal against the ribbon to print the letter. Ref. Electronic Instrumentation by H S Kalsi Daisy Wheel
- 8. Line Printers In line printers, characters or spaces constituting printable lines are printed simultaneously across the entire line. Paper is spaced up and the next line is printed. An embossed type font is positioned across a line for‘printing by using embossed type, either on a carrier consisting of a chain, train or band moving horizontally across the paper and print line, or a drum rotating in front of the paper with characters embossed. Typically, there are 132 columns on the drum. As the drum rotates, the column of characters pan vertically across the paper and the print line as shown in figure. In both methods, hammers (one for each. Of 132 print positions) strikes when the correct character is positioned, imprinting the character on the paper with an inked ribbon. Ref. Electronic Instrumentation by H S Kalsi
- 9. Ref. Electronic Instrumentation by H S Kalsi Line Printers
- 10. Print characters are embossed on the band. The band revolves between two capstans, passing in front of the paper. An inked ribbon is positioned between the moving band and the paper. As the print characters on the band move by 132 horizontal print positions, the 132 corresponding print hammers behind the paper strike the band at the appropriate time, causing the line of characters to print each desired character in I32 print positions. In band printers, a metallic or plastic band has a fully formed etched character on it. The band rotates at high speed. There is one hammer for one print position, because several hammers can strike simultaneously for many print positions. These printers are faster than dot matrix printers. Ref. Electronic Instrumentation by H S Kalsi Line Printers
- 11. Ref. Electronic Instrumentation by H S Kalsi Drum Printer
- 12. Drum Printer Figure illustrates a drum printer. Each of the 64 or 96 characters used is embossed in 132 columns around the drum, corresponding to the print poslttons. The drum rotates in front of the paper and ribbon. Print. hammers strike the paper, imprinting characters from the drum through the ribbon and formmg an impression on the paper. The drum printer uses a cylindrical drum which contains characters embossed around it. There is one complete character set for each print position. To print characters, magnetically driven hammers in each character position strike the paper and ribbon against the spinning drum. An entire line of characters can be printed during each rotation of the drum. The drawbacks of drum printers are that the fonts are not easily changeable, and the print lines may be wavy. Ref. Electronic Instrumentation by H S Kalsi
- 13. Ref. Electronic Instrumentation by H S Kalsi Dot-Matrix Printers
- 14. Dot-Matrix Printers Dot matrix characters are formed by printing a group of dots to form a letter, number or other symbol. This method is widely used with mini and micro computers. Dots are formed both by impact and non impact print methods and are both character at a time and line at a time printers. Figure shows the letter ‘A’ formed by a dot-matrix, five dots wide and seven dots. high (5 X 7) and in a 9 x 7 matrix. A 5 x 7 dot- matrix is frequently used when all letters are acceptable, in upper case. Dot-matrix printers can print any combination of dots with all available print positions in the matrix. The character is printed when one of 128 ASCII codes is signalled and controlled by the ROM (read only memory) chip, which in turn controls the patterns of the dots. By changing the ROM chip a character set for any language or graphic character set can be used by the printer. Ref. Electronic Instrumentation by H S Kalsi
- 15. Non Impact Dot-Matrix Printers Non-impact dot-matrix printers cause a mark without directly touching the paper. They are therefore quiet compared to impact printers. They cannot make carbon copies, however, as there is no force to impress the character through multiple carbon copies. NIDM printers are useful for printing single copies of computer output, for recording the output of printing calculators and video displays, and for logging industrial data. There are four types of NIDM printers thermal, electrosensitive, electrostatic, and ink jet. Ref. Electronic Instrumentation by H S Kalsi