Simple VCO using schmitt trigger using 74HC14

The oscillator or the frequency generator, By most popular use NE555 or transistors or various gate. The output frequency setting depend on the resistance or capacitance As well as use the crystal control or frequency to the circuit. The frequency generator will see that has Designs commonly used in an electronic circuits, specifically the digital circuit.

This is Simple VCO circuit using schmitt trigger as Figure 1 is Voltage controlled Oscillator (VCO) by use the 74HC14 IC, which inside the IC include up to 6 schmitt trigger, but applied just only one can also be the frequency controller by voltage.

The pulse signal waveform in Figure 1, At point A, input voltage start at 0 volts. The output of inverter will be “high”, when has voltage signal come to an input or use the voltage control-VC, or at place A has voltage rises.

Simple VCO using schmitt trigger using 74HC14


Figure 1 The VCO-using schmitt trigger

The capacitor-C1 will charge through a resistor-R1. But when voltage rises until the maximum value to trigger to the inverter gate works or is voltage-VT+ output from inverter will into as “low” and C1 will discharge through R2 and diode- D1 which is in briefly range.

The resistor-R2 affects a frequency of control voltage-Vc, capacitor-C1 and Properties of the inverter will affect the width of pulse frequency to output. The correlation between control voltage and output frequency, see in table below. The power supply of circuit is +5 volts, The voltage is controlled in range of 3.5-12 volts, and frequency output of 1.28-10.1 Khz.

components-layout-of-vco-schmitt-trigger-circuit
Figure 2 the components layout of the VCO using schmitt trigger

How to builds
Although this project is a experiments. Normally we are always on the breadboard. But sometimes we make the actual use on the purpose PCB board as Figure 2 is the components layout of this project. Which detail of building I do not described because it has same characteristics of before circuits. You will not be bored of it. But you shouldn’t negligence the project carefully.

The component list
Resistors, size ¼ W +5%
R1____________100K
R2____________1K
Capacitors
C1______0.01uF 50V Polyester
Semiconductors
D1_________1N4148____ 75V 150mA Diodes
IC1________74HC14__Hex inverting Schmitt trigger
Other
a perforated board

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