Category Archives: Circuit Diagrams

Useful circuit diagram for developer and easy applicable

The Circuit Diagram of Medium Power FM Transmitter

Schematic Diagrams      Comments Off on The Circuit Diagram of Medium Power FM Transmitter

This is a simple circuit diagram of a moderate power FM transmitter circuit employing two transistors. This device will convert your analog signal voice and transmit it with FM modulation. The voice signals picked by the microphone will be amplified by the transistor Q1. The second transistor is wired as… Read more »

Photo Relay Circuit Diagram

Schematic Diagrams      Comments Off on Photo Relay Circuit Diagram

A photo relay or light will activated the Normally Open relay in the circuit to become closed / contact according to the light. in this circuit a photo diode is used to sense the light. The photo diode offers a high resistance when there is no light falling on it…. Read more »

Solar Panel Current Meter Circuit Diagram

Schematic Diagrams      Comments Off on Solar Panel Current Meter Circuit Diagram

This circuit is used to measure the current from a solar panel. It has very low power loss for currents in the 0-10A range. It also works as a general purpose DC current meter. The circuit can be used on either the positive or negative side of a DC circuit…. Read more »

The Circuit Diagram of Simple Buzzer

Schematic Diagrams      Comments Off on The Circuit Diagram of Simple Buzzer

This novel buzzer circuit uses a relay in series with a small audio transformer and speaker. When the switch is pressed, the relay will operate via the transformer primary and closed relay contact. As soon as the relay operates the normally closed contact will open, removing power from the relay,… Read more »

The Circuit Diagram of Telephone Conversation Recorder

Schematic Diagrams      Comments Off on The Circuit Diagram of Telephone Conversation Recorder

This telephone conversation recorder circuit diagram enables automatic switching-on of the tape recorder when the handset is lifted. The tape recorder gets switched off when the handset is replaced. The signals are suitably attenuated to a level at which they can be recorded using the ‘MIC-IN’ socket of the tape… Read more »

The Circuit Diagram of Battery Low Voltage Beeper

Schematic Diagrams      Comments Off on The Circuit Diagram of Battery Low Voltage Beeper

This circuit provides an audible and visual low voltage warning for 12V battery powered devices. When the battery voltage is above the set point (typically 11V), the circuit is idle. If the battery voltage should fall below the set point, the LED will light and the speaker will emit a… Read more »

The Circuit Diagram of Radio Wave Alarm

Schematic Diagrams      Comments Off on The Circuit Diagram of Radio Wave Alarm

The circuit transmits on Medium Wave (this is the small problem with the police). IC1a, together with a sensor (try a 20cm x 20cm sheet of tin foil) oscillates at just over 1MHz. This is modulated by an audio frequency (a continuous beep) produced by IC1b. When a hand or… Read more »

The Circuit Diagram of Scale Battery Voltmeter

Schematic Diagrams      Comments Off on The Circuit Diagram of Scale Battery Voltmeter

This circuit is used to measure the voltage on a 12V (nominal) lead acid rechargeable battery system. It was specifically designed for use in solar powered systems, but is general enough that it can be used for automotive or other 12V systems. Lead acid batteries normally spend their working lifetime… Read more »

Capacitance Meter Circuit Diagram

Schematic Diagrams      Comments Off on Capacitance Meter Circuit Diagram

This project is more complex than the others described earlier. However, when finished, you will have an instrument capable of measuring all but the largest capacitors used in radio circuits. Unlike variable resistors, most variable capacitors are not marked with their values. As well, the markings of capacitors from salvaged… Read more »