1.3-12V Small Variable Power Supply

This is a small variable power supply delivers adjustable output voltage of 1.3v-12v. The current output determined by R3. With current setting (see part list), it will deliver current output about 1A.

220V Light-Operated On/Off Switch

This schematic diagram is a light-operated, remote-controlled solidstate switch circuit to handle lamp. While in darkness, the resistance of Light Dependent Resistor (LDR) is extremely hight, it shoots up to megohm range. As a result, the triac isn't going to have gate drive and therefore it doesn't conduct.

Gold Detector Schematic

Here the very simple and easy build gold detector circuit. The circuit capable to sense gold or metal or coins from a distance of about 20cm, depending on the size of the object to detect.

The circuit oscillates at about 140kHz and a harmonic of this frequency is detected by an AM radio. You can simply tune the radio receiver until a squeal is detected.

Simple Intercom Circuit with Transistors

This is a 2-station simple intercom circuit build based on transistors part and using common 8R mini speakers. The speaker works as microphone and generate sound, so there is no need microphone for this intercom. The "press-to-talk" switches should have a spring-return so the intercom can never be left ON, push on switch can be used for this kind of task.

Interior Light Fader for Automobile

Here the circuit diagram of Interior Light Fader for Automobile. The circuit is build using low power operational amplifier LM324 which only need around 3mA of current, so it won't bother the battery supply if left connected for extended periods. This circuit is similar to the fading eyes circuit above and is used to slowly brighten and fade interior lights of older cars.

Dynamic Mic Amplifier (To Use Speaker as Microphone)

This is the circuit diagram of dynamic mic amplifier. This simple and easy built circuit can be used as a subtitute of an electret microphone. It will turn an ordinary mini speaker to become a pretty sensitive microphone.

Basic Oscillator Circuit using Two Transistors

This is the schematic diagram of basic oscillator circuit which using two transistors. When two transistors and a couple of passive components are connected as shown in the figure, the circuit starts to oscillate. The frequency of oscillation can be adjusted by changing the values of either the resistor or the capacitor.

One Transistor LED Flasher Circuit

Here the schematic diagram of one transistor LED flasher. This circuit can be the simplest circuit led flasher over the world.... :D

This is a novel flasher circuit working with a single driver transistor that will take its flash-rate from a flashing LED. The flasher in the photo is 3mm. An ordinary LED is not going to work. The flash rate are not able to be altered by the brightness of the high-bright white LED can be adjusted by replacing the 1k resistor across the 100uF electrolytic to 4k7 or 10k.

Magic Lights Circuit using Bi-Colour LED

This is the magic lights circuit which use bi-colour LED as the output to provide the light. The circuit uses 14 bi-colour (red and green) LEDs having 3 terminals each. Various dancing colour patterns are generated utilizing this circuit considering that each LED can create three various colours. The middle terminal (pin 2) of the LEDs will be the common cathode pin that is grounded. When a positive voltage is applied to pin one, it emits red light. Similarly, when positive voltage is applied to pin 3. it emits green light. And when positive voltage is simultaneously applied to its pins 1 and 3, it emits amber light.

Simple Audio Booster

This is a simple and low-cost audio booster circuit design. The circuit is based on general purpose amplifier and switches, 2N3392 transistor packed in TO-92. This circuit should be installed before power amplifier module.

Cricket Chirping Sound Generator

This is the circuit diagram of cricket chirping sound generator based on IC 4060, a 14 stage ripple counter and oscillator IC. A suitable audio wave form is produced by IC2 and related electronic components, driving the mini speaker through Q1. To allow a more real-life behavior, the chirp is interrupted in a pseudo-casual way by two timers built around IC1C and IC1D, whose outputs are mixed into IC1B and further time-delayed by IC1A, driving the reset pin of IC2.

19W Power Amplifier based LA4440

This is the 19W power amplifier circuit built based power IC LA4440. The LA4440 output configured in bridge connection. The LA4440 can be used for stereo amplifier and it will give power output of 6W on each channel. But if you use this power IC in bridge mode, the it will deliver power audio output up to 19W. Recommended supply voltage is 13.2V, 2A and heatsink should be mounted on the power IC.

15W Audio Amplifier with STK055

Here the schematic diagram of 15W audio amplifier, built based on single power chip STK055 from Sanyo.The STK055 is old power amplifier chip which still available on the market because of the ease of its usage and the performance is good. This chip requires heatsink to be mounted on its body.

Mice Repellent Circuit

This is the circuit diagram of mice repellent. Mice are animals that are very annoying, because sometimes he is damaging the object stored in the form of archives that are still valuable.

Surround Sound Processor Circuit

This is the easy build surround sound processor circuit using the digital delay process method. This audio processor isn't applying any unique function ICs that tough to obtain parsonaly, and designed in only common purpose ICs.

The kind of this Surround Processor is producing the surround impact with processing two channels of stereo supply. The majority of those are generates the surround impact with separates reverberations from supply signal and applies any processes, after which mix it to front channels or output as rear channel.