[Tutorial] Making a Digital Counter Up 0 to 9 using IC 7490

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Description counter 0-9
This counter 0-9 in easy to assemble, basic to use for other more complex where we make use of integrated circuits didactically as these could be replaced by other more complex circuits with simple application of microcontrollers.
Counter operation 0-9.
This counter circuit is formed by a generator essentially comprises a wave 555 which functions as a circuit astable multivibrator operating this type is characterized by an output square waveform with width defined by the designer.The outgoing wave frequency can be controlled by the resistor is connected between pins 7-8 and 2-7 in addition to the electrolytic capacitor connected to pin 2 of land. The pulse output can be varied by 100K ohm potentiometer (RV1).
Circuit counter



The 7490 is a counter asynchronous decades BCD to binary, this counter counts the falling edges of the clock pulses generated by 555, 4 outputs move counter to count in binary 0 in BCD (0000) to 9 BCD (1001). To counter operation must connect pins 2, 3, 6 and 7 to ground, but if we reset the counter (set the counter to zero) we can connect pins 2 and 3 to a high level (logic 1)
The 7447 is a decoder BCD to 7 segments. Receives as inputs the 4-bit counter output 7490 to form a coded bit (BCD, Binary Coded Digit) output of 7490 (binary counter) and outputs the same number (digit) presented on thedisplay 7 segments . May be the case that our counter does not do its job properly, in which case it may be by bad contacts, in which case a solution can be not stop pins 3, 4 and 5 of the decoder in the air and connect them feed point positive.
Materials counter 0-9
Important Notes
  • The pins 8 and 16 of BCD decoder 7447 U1 must be grounded and positive respectively source.
  • Pins 5 and 10 BCD counter U2 7490 must be connected to the positive supply and ground in that order
  • In the diagram of the counter notice that no diplay has no resistance, but should put a resistor (resistance value is recommended can vary from 200 ohms to 1000 ohms) between the display and the power meter.
  • While the 555 can withstand voltages greater than 5 volts, the BCD counter 7490 and 7447 BCD TO 7-segment decoder will support it because they are not TTL technology.
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