希洛·尤尔的基于VHDL的计程车计价器设计(15)

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重庆邮电大学本科毕业设计（论文）

input terminals J, K and L, respectively, a high is generated to reset the counter and change the state of the flip-flopsuch that Q becomes low.Hence, 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 flip-flop 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 4-digit displays that give the sum of money required from each passenger separately as well as a one six-digit display that gives the total income 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 display by5 volts through terminals 1, 2 and 3, respectively.

The corresponding display will be unblanked by supplying a low level of voltage through terminals A, C and G, respectively. Keeping terminals 8, D and H, respectively, at low level will keep them reset to zero. The corresponding display is then enabled by removing the low voltage from terminals B, D, and H, respectively, to be ready for counting the sum of money required from the corresponding passenger starting from zero.

The counting pulses for these three displays are supplied through terminal P. The total sum display will be enabled whenever any of the three displays is enabled (this is done by a 3-input OR gate as shown in Figure 8). Retaining the contents of the last display will be done by unblanking it by supplying a low level of voltage to terminal I as shown in Figure 10 b.

F. Changing Over Between Time and Distance Fares

In the following part, two different methods for changing over between time andistance fares are suggested:

The first is to switch to time fare whenever the distance fare is less than the time fare. Hence, a simple look to fares table (Table 2) can show that time fare should be used whenever the taxicab moves with speed less than 50 m/min. A possible circuit

that can perform this switching action is shown in Figure IO c. It contains one rpm limit switch

and a one inverter as well as two 2-input AND gates.

The contacts of the limit switch are normally closed and will be opened whenever the angular

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重庆邮电大学本科毕业设计（论文）

speed of the speedometer cablexceeds 50 rmp. The second alternation is to connect the input of the inverter in Figure 10 c. to the output terminal Q of the speedometer circuit, Figure 2. In this case, the switching into time fare will be done whenever the taxicab is at stand still.

G. Function of the Rotary Selector Switches The voltage levels that should be supplied by the terminals of the rotary selector switches in order to ensure proper operation by the electronic

circuit are given in Table 3. Connection of three rotary selector switches each witb four decks of

five poles each, that satisfy the logic function of Table 3, is shown in Figure 10 a. Rotating any of the three switches into fully clockwise direction will pass through five positions. The function of the rotary selector switches can be described starting from the first position passing through variousteps until reaching the final position as follows:

Initial position: In this position a low voltage level is applied to terminals I, 2 and 3, this will disconnect the 5 volts supply from the three first displays, set the three inputs of the number of passenger detection circuit CTI to low level. A low voltage level is applied to terminals 8, D and H, this is to ensure that the total income display is disabled. Voltage levels at terminals A, C, G and S are at no care condition.

Step I: Rotating any of the rotary selector switches one step toward clockwise direction will supply 5 volts to the corresponding display, provides a high level voltage at terminals 1, 2 or 3 indicating that one passenger have entered the taxicab. A high level voltage should be applied to terminals A, C or G in order to ensure that the corresponding display is still blanked. Other terminals B, D, H and S are kept unchanged. Step 2: Rotating the rotary selector switch one step further, will change the state of voltages at terminal A, C or G to be at low level and unblanks the corresponding display. States of voltages at terminals I, 2, 3 and S are remained unchanged.

Terminals B, D and H should be remained at low level to ensure that the corresponding readout

is cleared to zero while unblanking the display.

二、中文翻译

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重庆邮电大学本科毕业设计（论文）

摘要

本文提出了一种出租车多通道计价的方案，能同时处理一个以上乘客的情形。 为了从理论上说明本方案，提出了一个实验上的三通道型的士的完整设计（其原型是根据埃及科学和技术研究学院的研究而建成得）。

1 .导言

在不发达的国家，早上把人们从他们家送到工作的地方，然后下午送回来已成为一个大问题，尤其是在大城市。

作为解决这个问题的一个部分，在某些国家出租车用来解决这个问题，送人们从一个地方到另外一个地方。 例如，出租车的四个席位可携带四个不同的没有任何关系的乘客，除了他们的路线是相同的。

因此，依靠目前的传统的单车道计价以确定所需的票价，把每个乘客的计费分开，这已成为一个非常困难的问题。因此，在出租车司机， 车主，乘客和国家税务部门之间存在着不公平的财政关系。

在这种情况下，出租车司机强迫乘客支付多于他们所应付的。在某些情况下乘客支付了他们应付车费的双倍。

本常规单频道计程车，出租车司机不能够确定出租车日常收入。 在某些情况下（出租车的4个席位） ，他们可能只有出租车四分之一的收入 （ 大部分的出租车司机）。从这些支付工资的出租车司机以及作为燃料费用外，还要维修以及汽车折旧等费用。事实上，出租车业主并非 …… 此处隐藏：4818字，全部文档内容请下载后查看。喜欢就下载吧 ……