Simple counter design and production, CD4516 Counter
Keywords: counter circuit diagram, CD4511, CD4516
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Author: Wan Dong Wang Wei
The counter enables functions such as button count, increase or decrease control, hand / automatic cleaning. Need to prepare the following components: a common cathode 7-segment digital tube, button switch, CD4511 (BCD latch / 7-segment classification / driver), CD4516 (preset 4-bit binary plus / minus counter), CD40106 (or 7414, six-reverse Schmocyte trigger), CD4001 (or 7400, four 2 input and non-door), CD4093 (or 74132, four and non-simplete triggers) and a bread plate, resistance, and capacitance. In addition, it is also necessary to prepare a + 5V voltage regulator power supply, or a homemade power module. This circuit is the core with the counter integrated block. The input is: count, clear, increase or decrease three buttons, and the output is processed by the decoded drive Displayed by the digital tube. The schematic diagram is shown below.
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First, the counter can increase or decrease the count according to the design requirements, and the reversible counter should be selected. This design selects the preset 4-bit binary plus / reduce counter 4516, as shown below. The count pulse is input from the CP, and each of the pulses rises, the binary output data changes 1. If the U / D terminal is high, add 1; vice versa. Rd is an asynchronous clearance end, and Rd is high, and the counter is cleared. This design is to control the three inputs. Further, other control terminals should also be reasonably set: LD is a preset control terminal of asynchronous data. When the LD is high, the data on the DO to D3 is placed in the counter, which is the counting control terminal, the counting operation of the counter, Ci = O, when the count, Ci = 1 is allowed, held. As for the setting, it is still a low level, please consider it.
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Second, the button control button switch typically has two kinds, one is the low level, the press is high, as shown in the following figure (a), the A point is the control signal input terminal; another In contrast, the usual is high, and the following is low, as shown in the following figure (b). The reader can choose the pickup of the pulse button itself, but the clear button must be posed (a) to pick up, the reader can analyze the reason it is.
Third, the 4-bit binary data output from the decoding drive counter cannot be sent directly to the digital tube, and 4516 cannot drive the spotlight. This design selects 7 segment / driver 4511, and the pin is arranged as shown. Where Al, A2, A3, A4 are BCD code input, and A1 is the lowest bit. LT is the lamp test end, when the electricity is usually displayed, the display is displayed, and the display has always displayed the digital "8", and each pen section is illuminated to check if the display is faulty. BI is the blanking function, low timing makes all pen sections, and the BI should be higher than when the normal display is normal. Further, 4511 has the characteristics of rejecting the pseudo code. When the input data crosses the decimal number 9 (1001), the display gland is also blamed. Le is a latch control terminal, high-speed latch, low-speed transmission data. A ~ G is 7-segment output, which can drive a total-rich LED digital tube.
In addition, as shown in the figure below, 4511 displays the number "6", the A, B is blamed; when the number "9", the E, D segment is blamed, so 6,9 These two gangs are not beautiful. If you need to design a normal digital display, you can choose 4026, 4033 as a decoding drive; if you need to drive the common anode tube, 7447, 7449, 7446, 74247, and the like.
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Fourth, seven-stage digital tube to show the most commonly used devices is the seven-stage digital tube, which is composed of A, B, C, D, E, F, and G seven LEDs. By making different LEDs to illuminate, the display effects of numbers and letters are achieved, as shown in Figure 5. The general LED rated voltage is about 2.7V DC, so we are in series with a voltage resistor during use. The resistance is generally selected about 400 Ω, and if you need to highlight or scan display, the resistance can be appropriately reduced. The seven-segment digital tube has two types of CC and CA. The CC type is a common cathode digital tube. The cathode of each LED is joined together, and the anode is controlled by the anode, as shown in the following figure (a); the CA type is a common anode, opposite to the CC shape, as shown in the following figure (b). It can be observed that the pins are arranged substantially the same, but only the common ends are power and ground. If you don't know the type of digital tube, you can perform a simple test: 3 feet or 8 foots, one-on-one, one end pick + 5V power supply, one end touch other pins, if it is bright, It is a common sun. The method can also determine the pins corresponding to each LED one by one.
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V. Button anti-shake If the reader completes the design according to the above steps, the basic count function has been implemented. However, there will be a serious problem in the actual test. Each button is pressed, the number will jump, and the action is no longer avoided when the button is, why? This is because the pressing of the button will generate the jitter of the time-off time, as shown in the above figure (a), and the conditional reader can observe using an oscilloscope. Jitter causes the count interference and pressing a key may count. In order to eliminate the impact of jitter, the integrating circuit can be used to eliminate jitter, as shown in the following figure. The capacitor in the integrating circuit is charged before saturating, thereby turning the shake portion into a smooth curve, as shown in the above figure (b). The jitter time is generally 10 ~ looms, so this design is selected to select r = 330Ω, c = 10μF (if you use a electrolytic capacitor, please pay attention to the positive and negative pole to be reversed), the Schmitt trigger selection 40106 (also available 7414).
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Sixth, automatic clearance in the test, carefully readers will find that after the increase is 9, the button number will not change, why? The reason is very simple, 4516 is a 4-bit binary counter, and the output data may exceed 9, and the drive circuit cannot be driven for 9 or more numbers. Solving this problem requires an automatic cleaning circuit to automatically return to zero when the circuit reaches 10. Obviously, the true binary output at the time of output 10 is "1010", and therefore, Q3 and QL can be taken as a trigger signal, and when both are 1, the RD end of 4516 provides high electricity clearance. Please be designed by the reader, it is recommended to use or do not use or do it, but use common and non-door. Considering Schmidt's non-door co-ordination in the button shook, think I want to complete the anti-shake and clearing only with a integrated circuit? Can I do it? Can you do it? 44132,4093)? In addition, when the count is reduced, the function of 0 automatic 9 is difficult to implement, and the ability is stronger to challenge.
Seven, multi-bit display in practical applications or competitions, often need to make multiple digits, which requires multiple digital tubes, and must decode the driver multiple 4511bcd. Each 4511bcd requires 4 villion data lines, and the N-bit digital tube display requires a 4N binary data cable. In order to simplify the hardware, the 4511bcd latch control terminal Le (5 pin) can be controlled to complete the parallelization of the data cable. The control of the scan signal is done by means of the decimal counter CD4017, as shown in the following figure. The reader can extend the display circuit according to this block diagram, which needs to be reminded that the scanning multipart display Although the line and device resources are saved, the complexity of data transfer and control is added, and the digital tube brightness is also significantly weakened.
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This article is easy to difficult, step-by-step completion of a simple counter with button input and digital tube data output functions, and makes it necessary for its practicality, such as button anti-shake, automatic cleaning, multi-bit display, etc. The design is simple, easy to learn, good transplantability, strong extensibility. Not only is it suitable for the introduction of electronic design; it can also be flexibly split, which is directly used as an input module and output module of electronic design. This simple counter circuit schematic picture below.
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