Audio FM transmitter with Stereo Input

Quality Audio FM transmitter Circuit
This house FM transmitter for your stereo or any other amplifier provides a good signal strength up to a distance of 500 meters with a power output of about 200 mW. It works off a 9V battery.

Solar Charger with Current Regulation & Cut-Off

Solar Charger with Current Regulation & Cut-Off

Here is a solar charger circuit that is used to charge Lead Acid or Ni-Cd batteries using the solar energy power. The circuit harvests solar energy to charge a 6 volt 4.5 Ah rechargeable battery for various applications. The charger has Voltage and Current regulation and Over voltage cut off facilities.

30V 1A Transformerless Power Supply

This transformerless power supply circuit is designed for medium current applications. During the negative half period, the capacitor C5 is charged to peak voltage network.
The positive half wave will open the thyristor and the electric charge accumulated in C5 will be transferred in C4. The transport of electric charge through the thyristor begins when the voltage on C4 drop below a specified level of voltage (set by zener D4). Thus the output voltage does not depend too much on the voltage variations or the output load.

TransformerLess Power Supply 12V 100mA

This is a transformerless power supply for low current applications. C1 is the X rated AC capacitor that reduces high volt AC. D1-D4 rectifies AC to DC and C2 removes ripples. R1 is the bleeder to remove stored current in AC when power is off. R2 limits inrush current. A Zener can be used in the output to get regulated DC.

SuperFast Rechargable Battery

SuperFast Rechargable Battery Using GoldCap Capacitors

When compared to conventional disposable or rechargeable batteries, GoldCap capacitors offer a very rapid charging while delivering a high peak output current which makes them an interesting alternative power source.

1.5 Watt 1-2 km Range FM Transmitter

Here is a well designed FM transmitter circuit that works effectively in 1 – 2 km range.
Input source is an electret condenser microphone and signal gain can be adjusted by using the potentiometer P1. You can easily prepare the PCB by using any PCB editor and apply it to the board by using the ironing method. The coils and the antenna can be designed as a part of the PCB made up of the copper area.

FM Telephone Transmitter

"Telephone Transmitter, FM."
"Receive telephone conversations on any FM radio with this neat little device." 
Would you like to be able to amplify a phone call so everybody can hear it? Or perhaps you'd like a way to record phone calls for record-keeping purposes. If either idea sounds good to you, then you might want to build the FM Telephone Transmitter describe in this article. It's a simple, yet ingenious device that connects in series with a phone line, "reals" power from the latter, and transmits both sides of a conversation to an FM radio tuned to between 90 and 95 MHz.

Audio equalizer with transistors BF245 - BC109

2 Watt FM Transmitter

The circuit is basically a radio frequency (RF) oscillator that operates around 100 MHz. Audio picked up and amplified by the electret microphone is fed into the audio amplifier stage built around the first transistor. Output from the collector is fed into the base of the second transistor where it modulates the resonant frequency of the tank circuit (L1 coil and the trimcap) by varying the junction capacitance of the transistor. Junction capacitance is a function of the potential difference applied to the base of the transistor T2. The tank circuit is connected in a Hartley oscillator circuit.

SpeakerBox Filter Designer

 SpeakerBox Filter Designer is a simple and useful software for calculate the first and second order passive audio filter for 2 way and 3 way speaker box .
Speaker Box Filter Designer audio filter calculator is a very simple program that provide a simple calculations of values for all components used in passive audio filters for speakers .
Also with this audio filter calculator software you can calculate the numbers of turns required by coils used in audio filters .

Portable FM Radio

The KA22429 is a monolithic integrated circuit designed for Portable FM radio receiver.
It is consistng of RF input stage, Mixer, IF, Mute control and Loop (earphone drive) AMP.
It is suitable a pocket - size radio.

USB Powered Audio Amplifier for PC

This audio power amplifier might be good solution to all of those who have PC with integrated sound card into motherboard. The main problem is that outputs of such sound cards are for active acoustic systems, this means that speakers must have power amplifier built in. If you decide to connect a headphones sometimes it might be not enough to provide required sound level.

FM Transmitter 4Watt

Stabilised tendency of catering: Vcc=12~16V
Frequency of emission: 88~108MHz
Consumption: 100~400mA
Circuit diagram:

SPY FM Transmitter (1.5V)

Spy FM Transmitter Circuit Schematic With Explanation

3 LED Battery Monitor

Monitor the voltage level of an automobile battery using 3 LED battery monitor circuit

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