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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 co...

The electronic circuit provides a visual time 9 second delay using ten LED before control by closing a 12 Vdc relay. That the reset switch has closed, IC 4017 decade counter will be reset to zero count which illuminates the LED driven from pin 3. IC 555 timer output at pin 3 will be high and the voltage at pins 6 and 2 of the timer will be a little less than the lower trigger point, or about 3 Vdc. 9 Sec Timer with LED Indication and Control Relay Circuit Schematic   That time the switch is opened, the transistor in parallel with the timing capacitor (22uF) is shut off allowing the capacitor to begin charging and the IC 555 timer circuit to produce an approximate one second clock signal to the decade counter. The counter advances on each positive going change at pin 14 and is enabled with pin 13 terminated low. When the 9th count is reached, pin 11 and 13 will be high, stopping the counter and energizing the relay. Longer delay times can be obtained with most capacitor or most resi...

Here i share power amplifier based on IC TDA7236 . This amplifier require minimum voltage 0,9 volt and maximum voltage is 1, 6 volt , its very low voltage amplifier. You can use this amplifier everywhere just with one battery 1,5 volt. Power output 16 mW with 32 ohms impedance. see circut below :