An astable multivibrator, put to work by using it as a source of clock pulses for a 4017 counter, is the basis for this circuit.
We can use it to generate random numbers in a range of one-of-ten or as a 0-to-9 counter in science projects or in other applications. You can also adjust the clock so that it supplies one pulse each second for using the circuit as a timer in scientific experiments oral home.
If you alter the clock pulse frequency, time range can be changed so that it supplies one pulse each minute or ten minutes. In this case, the time range will rise to 9 minutes or 90 minutes (in 1- or 1O-minute steps)!
As a sequence generator in logic circuits demonstrations, you can change the astable operation of the 555 to monostable, connecting a momentary switch or any sensor that can be used to trigger it.
The circuit can be powered from 6 to 12V supplies, and R3 depends upon the voltage of the power supply. Use a 470 ohm resistor if the supply voltage is 6V.
Use a 1,000 ohm resistor if the power supply used is 12V.
Capacitor C1 determines the pulse rate range and can be altered. Values between 1 and 1,000uF can be used. Remember that higher values mean lower pulse rate.
Pl adjusts the pulse rate within 100:1, depending on the capacitor used. Figure I shows the schematic diagram of the Sequence Generator. The circuit uses a 555 IC timer to generate the clock pulses and a 4017 CMOS IC, a counter and 1-of-10 decoder to drive ten LEDs as indicators.
Components placement on a homemade printed-circuit board is shown in
circuit 2, You can also use a solderless board or breadboard to mount it.
Positions of the polarized pieces, such as the LEDs and electrolytic capacitor, should be observed.
Parts List - Sequence Generator
lC1 - 555 - Integrated circuit, timer
,C2 - 4017 - CMOS Integrated circuit, counter
LEDs - Common red, yellow or green
P1 - 1,000,000 ohm potentiometer
Rl,2 - 10,000 ohm, 114W,5% resistors
R3 - 470 ohm, 114W,5% resistor
Cl - 10uF/l6 WVDC electrolytic capacitor
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