This circuit is a variable time base oscillator circuit that has the operation as characteristics of high-frequency pulse oscillator generator out to a Decade counter circuit. So that sends a pulse signal appears at the output of one signal per the counting clock signal that as 10 pulses. Cause easy to building the lower signal to operate.
Therefore, if required the output sends the output signal with a 1 Hz frequency. We will adjustable the frequencies generator to build the high frequencies up to 10 times of the output frequency that is 0.1Hz.
How the variable Time base oscillator works
The circuit diagram
Start with the frequency generator which includes a NAND gate IC-CD4011 is IC1/1, IC1/2 together with R2, R3, VR1, and C1 will be controlled with a positive voltage or logic “1”. While normal SW1-switch does not push voltage at input pin equals 0V.
When enter the positive voltage into the circuit will generate the pulse signal output with a frequency. Which depending on the value of R, C as above.
By the circuits is designed to adjust easily frequency from the value of VR1. If it cannot change enough as you want. You can change the value of C1 or VR1 or both. Also, If you want a many output current. The output signal will have low frequencies. In another hand, low power it will cause high frequencies.
The signal that gets from the frequency generator will be the clock signal to enter with IC2 that pin 14 to get the Decade counter. The C2 acts as a filter a noise signal to ground. so that IC2 does not work error. While has and not has the clock signal input.
The LED1 will glow when has the signal out of pin 2 or will glow when has the output signal appears at pin 2 or has counting pulses No. 2. Which is the output pin no. 2 (Q2) of IC and when counting pulse no.3. The LED will get out. We can select to connects LED at output any legs. All output has 10 legs. array from pin 3, 2, 4, 7, 10, 1, 5, 6, 9, 11 in sequence.
Build CMOS Time base oscillator
You can build this project by put all parts on the universal PCB board as Figure 2 is components layout. The wiring and various components can view of the example in Figure 2. what to look out carefully for resistors, capacitors, and ICs correctly. Pin of the IC is not an error.
The components list.
Resistors ¼W +5%
VR1— dual potentiometer —500K
SW1–normally open pushbutton —1 pcs.
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