出租車計(jì)價(jià)器畢業(yè)設(shè)計(jì)中英文翻譯(編輯修改稿)
2025-06-26 15:39 本頁(yè)面
【文章內(nèi)容簡(jiǎn)介】 possible simplified boolean functions that gives minimum number of inputs to gates may be obtained from Table I. A possible logical diagram that is based on the above derived expressions is shown in Figure 5. It consists of two inverters, four 2input AND, to3input AND two 3input OR gates B. Tavelling Distance Scaling Circuit CT2 As shown from the block diagram of Figure 4, the circuit CT2 has four input J, K, L and E and one output M. The function of the circuit is to supply a single pulse at the output M for a certain number of pulses generated at the output of the speed sensor (certain number of meters travelled by the taxicab), according to the number of passengers hiring the car. A suggested fare per kilometer of travelling distance is shown in colomn two of Table 2. the circuit, in this case, should supply a single pulse at the output M for every 100, 125 or 143 pulses generated at the input terminal E according to the level of voltage at input terminale 3, K or L, respectively. Our circuit could be, as shown in Figure 5, three decade counters, connected as a three digit frequency divider whose dividing ratios 100, 125 and 143 are automatically selected by the voltage level at terminals J, K and L, respectively. A possible circuit diagram that may verify the above function is shown in Figure 6. It consists of three decade counters type 7490, one BCDto decimal decoder type 7445, three 4input AND, one 3input ANDone 2input AND two 3input OR gates. C. Time Scaling Circuit CT3 As shown in the block diagram, the time scalingcircuit will have four inputs J, K, L and F and one output N. The function of this circuit and accordingto colomn three of Table 2 (fare per 2 minuts of waiting time) is to supply a single pulse at the output N for every 120, 240 or 360 pulses supplied at the input terminal F from the I Hz clock according to level of voltage at inputs J, K and L, respectively. Time scaling circuit would be similar to the distance scaling circuit but with different diving ratios. A Possible circuit diagram is shown in figure 7. It consists, in this case, of three decade counter type 7490, two 3input AND, one 5input AND, one 2input AND one 3input OR gates. D. Circuit CT4 Which Generates Clock Pulses for Display Circuit The function of this circuit is to supply one, two or three pulses at the output terminal R for each pulse generated at any of the terminals N or M, according to the voltage level at the input terminals J, K or L, respectively. The output P will receive a pulse for each pulse generated at any of the input terminals N or M. This function can be performed by the circuit shown in Figure 8, it consists of one ripple counter type 7493, one half of a dual JK masterslave flipflops circuit type 7476, three inverters, three 2input AND, one 3input AND, one 2input OR and one 3input OR gates. When a pulse is generated at either input terminals N or M, a high level voltage will be generated at the output Q of the flipflop. This will g a t e t h e I Khz signal to be connected to the input A of the ripple counter as well as to the output terminal R. When one, two or three pulses are counted by the ripple counter, according to the level of voltage at the input terminals J, K and L, respectively, a high is generated to reset the counter and change the state of the flipflopsuch that Q bees , the 1 KHz signal is disabled to reach the outputerminal R or the input A of the ripple counter. In order to ensure the proper function of the circuit, the flipflop should be cleared whenever a new channel is operated. This has been achieved by the input 5 and will be explained later when describing the function of the channels rotary selector switchs. E. Display Circuit As shown in Figure 2, the display panel would contain three 4digit displays that give the sum of money required from each passenger separately as well as a one sixdigit display that gives the total ine of the taxicab. A possible wiring diagram for the display circuit is shown in Figure 9. Rotating any of the rotary selector switches to fully clockwise direction will supply the corresponding dis
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