基于at89c51單片機(jī)的數(shù)字電壓表設(shè)計(jì)外文翻譯-在線瀏覽
2024-12-25 13:33本頁(yè)面
【正文】 ightmost displays are connected so that they can display all the numbers from 0 to 9 while the first from the left can only display the number 1 and when the voltage is negative the 171。 sign. The whole circuit operates from a symmetrical ρ 5 VDC supply which is applied at pins 1 (+5 V), 21 (0 V) and 26 (5 V) of the IC. Construction First of all let us consider a few basics in building electronic circuits on a printed circuit board. The board is made of a thin insulating material clad with a thin layer of conductive copper that is shaped in such a way as to form the necessary conductors between the various ponents of the circuit. The use of a properly designed printed circuit board is very desirable as it speeds construction up considerably and reduces the possibility of making errors. To protect the board during storage from oxidation and assure it gets to you in perfect condition the copper is tinned during manufacturing and covered with a special varnish that protects it from getting oxidised and also makes soldering easier. Soldering the ponents to the board is the only way to build your circuit and from the way you do it depends greatly your success or failure. This work is not very difficult and if you stick to a few rules you should have no problems. The soldering iron that you use must be light and its power should not exceed the 25 Watts. The tip should be fine and must be kept clean at all times. For this purpose e very handy specially made sponges that are kept wet and from time to time you can wipe the hot tip on them to remove all the residues that tend to accumulate on it. DO NOT file or sandpaper a dirty or worn out tip. If the tip cannot be cleaned, replace it. There are many different types of solder in the market and you should choose a good quality one that contains the necessary flux in its core, to assure a perfect joint every time. DO NOT use soldering flux apart from that which is already included in your solder. Too much flux can cause many problems and is one of the main causes of circuit malfunction. If nevertheless you have to use extra flux, as it is the case when you have to tin copper wires, clean it very thoroughly after you finish your work. In order to solder a ponent correctly you should do the following: Clean the ponent leads with a small piece of emery paper. Bend them at the correct distance from the ponent’s body and insert the ponent in its place on the board. You may find sometimes a ponent with heavier gauge leads than usual, that are too thick to enter in the holes of the . board. In this case use a mini drill to enlarge the holes slightly. Do not make the holes too large as this is going to make soldering difficult afterwards. Parts placement PCB dimensions: 77,6mm x 44,18mm or scale it at 35% Take the hot iron and place its tip on the ponent lead while holding the end of the solder wire at the point where the lead emerges from the board. The iron tip must touch the lead slightly above the . board. When the solder starts to melt and f
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