Free Circuit Diagram

Capacitance meter can be very helpful in identifying old components where its mark has been erased or became unreadable. Such instrument can be quite expensive, but fortunately we can build it easily with much lower cost. The capacitance meter described here can measure any capacitor between 1pF and 10uF. Here is the schematic diagram of [...]

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 [...]

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 [...]

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 digital meters is lack of accuracy and resolution in comparison to drawing information upon a measurement’s rate of change or tracking a reading’s trend. To solve this problem, we should use analog moving-coil meters. Here is the schematic diagram of analog moving-coil meters : This circuit uses 8-inch moving coil meter [...]

Many analog ohm meters have non linear scale, so the resolution become worse at higher resistance value. This because they use cheap current source, only a series resistance to approximate an ideal current source. An ideal current source will force a consistent current amount regardless of the tested resistor value.  Using regulated current source, the [...]