The design of digital tachometer

1 turn ／ minute. 1 measure a principle be being measured to rotate an aluminum foil is stuck to regard as on the axis glance body, should glance body turns to photoelectricity sensor when ahead, the infra-red beam of light that photoelectricity sensor gives out is reflexed to come back, what be gotten on by photoelectricity sensor at the same time is infra-red receive a canal, generate signal of a pulse, the edge that we use this signal sparks odd the high accuracy timer of a machine interior undertakes timing, precision can amount to 1 μ S, should glance body turns to photoelectricity sensor again when ahead, the edge that uses reflection signal stops sheet piece machine time. The whirl of such runner shaft is periodic T is measured to come out by accurate ground, next odd a machine become rotate speed and be in charge of periodic conversion through LED number show come. 2 circuit are formed reach software to design circuit structure to see a picture 1, because ask bulk is cabinet and indication brightness is tall, accordingly, use scanning to show pattern, however, finish at the same time with a CPU measure and showing is no good, scanning function will affect CPU badly measure. Accordingly, the AT89C2051 that uses production of two ATMEL company is odd a machine will be held the position of respectively, AT89C2051 is had inside the EEPROM program memory of buy 2KB and 128 RAM of byte, and every cite a base can these good character such as the electric current of inspiratory 20mA. CPU1 rotates with what will measure runner shaft coming back periodic and conversion becomes rotate speed, transmit indication data to CPU2 next, CPU2 just is scanning ceaselessly at ordinary times indication data, when CPU1 sends data to come over, CPU2 generation is interrupted, receive data instantly, update indication data next, the data that goes up in canal of 4 LED number so was updated instantly. The profit that uses two CPU is circuit structure clarity, process designing is simple, came true modular design. Serial interface means is used between CPU 2, have communication in order to interrupt a form. The detailed list of communication share program of CPU2 is as follows: 3 conclusion course is used actually, the tachometer that we design achieved the goal that imagines beforehand, use convenient and reliable, and because such structural design makes,the mouth of input ／ output of CPU1 takes up few, because this still can extend its function. For example we installed a diverter switch, the function that increased photoelectricity tally (probe is common) . Additional, we still can reach CPU2 4 LED in all canal of in relief number forms a general indication module, except show 0 ～ 9 outside waiting for a number, still can show give typical examples to be like A - the character such as J, L, O, P, Q, R, U, Y. Such, if we are when the circuit with other designs, if want to use LED number canal to show, need not again process designing plate making, should use this general indication module only can, go to the lavatory simply. This kind of indication module if not augment input outputs buccal line, can undertake canal of 5 7 paragraphs of numbers shows at most. CNC Milling