A voltage controlled oscillator circuit that called as VCO, is the circuit that use voltage signal level from input to control an amount of frequencies that generate at output or the output frequency transform by voltage . The basis of a function generators circuit or an oscillator generator circuit to applied in testing a lot of circuit. And can generated frequency provided the Square wave , triangle wave, or sine wave.
The circuit in Figure 1 is the VCO circuit use to test working of electronics circuit. As the maximum oscillator generator about 1.2 KHz by use testing voltage under 9 volts. By first probe will connect directly to 9V battery terminal to the circuit tested or is input. the next probe is tester the voltage level that out of from the circuit is tested or its output.
This working principle.
The working of circuit has the IC1-CD4046 (CMOS MICROPOWER phase locked loops IC) as Frequency generator controlled by voltage. When no voltage at pin 9 of IC1. VCO circuit will not produce a different frequency. andWith a frequency of up to 1.2 KHz audio out peizo-BZ1. Frequency determined by C1, R1. The resistor-R1 If the pin 11 of IC2 is defined as the maximum frequency. R1 is connected at pin 12 is the lowest frequency.
The zener diode-ZD1 and ZD2 prevent damage from incoming voltage at the input of VCO. The potentiometer – VR1 adjust the current level is tested. This is useful when testing the circuit with high impedance. While work circuit will consume slightly current, only about 3 mA. The C1 filter current to IC1, diode D1 connecting to block the power supply the wrong the terminal.
How to build this circuit.
We experiment this projects on universal PCB as Figure 2 Which have a few components layout.
The components List
Resistors ¼ W +5%
ZD1, ZD2_______12V 1W
Two small probe.