基于at89c51單片機的數(shù)字電壓表設(shè)計外文翻譯-資料下載頁
2025-10-13 13:33本頁面
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【正文】 ait till it covers evenly the area around the hole and the flux boils and gets out from underneath the solder. The whole operation should not take more than 5 seconds. Remove the iron and allow the solder to cool naturally without blowing on it or moving the ponent. If everything was done properly the surface of the joint must have a bright metallic finish and its edges should be smoothly ended on the ponent lead and the board track. If the solder looks dull, cracked, or has the shape of a blob then you have made a dry joint and you should remove the solder (with a pump, or a solder wick) and redo it. Take care not to overheat the tracks as it is very easy to lift them from the board and break them. When you are soldering a sensitive ponent it is good practice to hold the lead from the ponent side of the board with a pair of longnose pliers to divert any heat that could possibly damage the ponent. Make sure that you do not use more solder than it is necessary as you are running the risk of shortcircuiting adjacent tracks on the board, especially if they are very close together. When you finish your work, cut off the excess of the ponent leads and clean the board thoroughly with a suitable solvent to remove all flux residues that may still remain on it. For the replacement resistors follow the table below: 0 2 V ............ R3 = 0 ohm 1% 0 20 V ........... R3 = Kohm 1% 0 200 V .......... R3 = 12 Kohm 1% 0 2020 V ......... R3 = 120 Kohm 1% When you have finished all the soldering on the board and you are sure that everything is OK you can insert the IC in its place. The IC is CMOS and is very sensitive to static electricity. It es wrapped in aluminium foil to protect it from static discharges and it should be handled with great care to avoid damaging it. Try to avoid touching its pins with your hands and keep the circuit and your body at ground potential when you insert it in its place. Connect the circuit to a suitable power supply ρ 5 VDC and turn the supply on. The displays should light immediately and should form a number. Short circuit the input (0 V) and adjust the trimmer P1 until the display indicates exactly 171。0187。. Parts List R1 = 180k P1 = 20k trimmer multi turn R2 = 22k U1 = ICL 7107 R3 = 12k LD1,2,3,4 = MAN 6960 mon anode led displays R4 = 1M R5 = 470k R6 = 560 Ohm C1 = 100pF C2, C6, C7 = 100nF C3 = 47nF C4 = 10nF C5 = 220nF If it does not work Check your work for possible dry joints, bridges across adjacent tracks or soldering flux residues that usually cause problems. Check again all the external connections to and from the circuit to see if there is a mistake there. See that there are no ponents missing or inserted in the wrong places. Make sure that all the polarised ponents have been soldered the right way round. Make sure the supply has the correct voltage and is connected the right way round to your circuit. Check your project for faulty or damaged ponents. Sample Power supply 1 Sample Power Suppl
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