Free Circuit Diagram

Controlling the speed of three phase ac motor is done by controlling the frequency of the power line supply,  since the motor is synchronized with the line frequency. Three phase ac motor speed controller is actually nothing more than three phase sine wave power inverter with variable frequency. The three phase power inverter is a [...]

This circuit is similar to our previous tone control circuit, a bass-treble tone control circuit, but here we present the formula for design your tone control’s custom frequency response. Here is the schematic diagram and formula of the tone control circuit: Almost all op-amp type can be used, as long as they have [...]

A phase control circuit can be used to control the power delivered to an AC load. The phase control circuit control the AC waveform, cutting the cycle to give full cycle, half cycle, zero cycle, or somewhere in between. You can say this circuit is similar to a dimmer circuit, but the switching is synchronized [...]

The high durability nature of a light emitting diode (LED) make it suitable for ON/OFF indicator application. Because the limitation on low operating voltage, LEDs are normally applied on low voltage application.  Fortunately, there is a simple method to apply LED indicator for high powerline voltage: reactance of a capacitor can be used to limit [...]

Notch filter is known as band-cut filter or band-reject filter. The fuction of this filter is to remove some frequency portion of a signal. The schematic diagram of this filter circuit, a second order notch filter is depicted in the figure below. The formula is actually complicated, but by taking the R3=R4 and [...]

The excellent high input impedance, high slew rate, and high voltage qualities of CA3140 op-amp make it suitable for Wien-bridge sine wave oscillator. The basic circuit for Wien-bridge sine wave oscillator is shown in the figure below (the upper part). You can see the formula in the figure, when R1=R2=R, and C1=C2=C, then the formula [...]