Free Circuit Diagram

This audio frequency meter uses 555 IC as a monostable multivibrator (one-shoot trigger). A monostable multivibrator can act as a frequency-to-voltage converter because it produce a fixed pulse width, with the repetition rate/density is proportional to the triggering input frequency. Here is the circuit’s schematic diagram: For resistor R1, because it set the [...]

The frequency formula of 555 oscillator is popularly known. For a known resistors and capacitor, the frequency can be determined by a formula. From the math logic, if the frequency and the resistors are known, then an unknown capacitor could be determined by the inverse of the formula. Anyone who has a frequency counter are [...]

Pulse width modulator produce a PWM signal, a pulse with a constant frequency but with the duty cycle vary according to a modulating signal. Here is the schematic diagram of pulse width modulator circuit using 555 IC as the active component: This pulse width modulator circuit need external pulse train input to trigger [...]

Testing whether a transistor is shorted or open usually done by ohm meter. You test if the base to emitter  or collector permit a current flow in one direction. Here is the circuit’s schematic diagram: The 555 timer ( IC1 ) operate as a 12hz  oscillator. The output of this oscillator (pin 3) [...]

Sawtooth wave oscillator  circuit can be implemented using several methods, here we present one design that employs 555 IC.  Here is the schematic diagram of the circuit: The core of the circuit uses  general 555 oscillator configuration, but instead of using a fixed resistor to limit the current for charging the capacitor, we [...]

This capacitance meter circuit is similar with previous meter circuit, but it uses transistors rather than logic gates. Here is the schematic diagram: You can see the circuit uses pnp transistor, you can use almost any pnp transistors with frequency bandwidth og 100MHz and collecttor current handling capability of 100 mA to replace [...]