Circuit shown above is static 0 to 9 display using a 7-segment capable of displaying number from 0 to 9. It has a lot of applications in day to day life and was implemented using two simple IC’s 7490 and 7446. This circuit works based on asynchronous decade counter 7490(IC2) a 7 segment display (D1) and a seven segment decoder/driver IC 7446(IC1). Static display circuit can also be used as a counter by controlling the clock pulse rather by giving the signal through a switch and 7-segment thus displays the number of counts or events took place.
As we know that seven segment display consists of seven LED’s labelled from ‘a’ to ‘g’ .By forward biasing the different LED’s at a sequence we can display the digits from 0 to 9.Here in this static number display circuit we are using Common anode 7 segment display. Initially the IC 7490(IC2) is a simple counter which is capable of counting digits from 0 to 9 cyclically. The IC 7490 counts the input pulses and sends the output as a 4 bit binary digit number from the pins 8 to 12.The chip counts to maximum number and return to zero after it.This can be done by using the reset pins 2,3,6,7,10.Here every pins are grounded so the the digits will be reset to 0000 after counting the maximum.
Output from the IC 7490 is fed in to the IC 7446 which is a simple decoder /driver IC.For every clock pulse the BCD output of the IC2 will advance by one bit and gives the BCD output. This BCD output will be decoded by the IC1 and it will drive the 7 segment corresponding form and will drive the display to indicate the corresponding light. The digit count can be increased by cascading two or more IC 7490 to it.This 0 to 9 static display circuit is very useful in day to day life and moreover it will give idea to think further and produce large display device.
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