Phone ringtone generator circuit

This is a simple home telephone ringtone generator circuit which is built with applying only several electronic components / parts.It generates simulated telephone ringtone and requires only DC supply with 4.5V DC to 12V DC voltage.One may possibly use this circuit in ordinary intercom or phone-type intercom. 

The sound is pretty loud when this circuit is operated on +12V DC power supply. Even so, the volume of ring sound can be adjusted.

Battery Indicator schematic diagram

This circuit diagramc shows a simple battery level indicator.In general, in mobile phones, the battery levels is displayed in dot or bar style.This helps you to effortlessly acknowledge the battery level.

6 Input Mixer

 

A simple mixer with 3 line inputs and 3 mic inputs using commonly available parts. 

Rain Detector schematic

Here's a simple rain detector circuit. It uses a sensor made of a small piece of etched PC board and a simple SCR circuit to detect rain and sound a buzzer. The SCR could also be used to activate a relay, turn on a lamp, or send a signal to a security system.

Lead Acid Battery Charger

Except for use as a normal Batter Charger, this circuit is perfect to 'constant-charge' a 12-Volt Lead-Acid Battery, like the one in your flight box, and keep it in optimum charged condition. This circuit is not recommended for GEL-TYPE batteries since it draws to much current. The above circuit is a precision voltage source, and contains a temperature sensor with a negative temperature coëficient. 

Variable Power Supply Circuit

This is the schematic diagram of variable power supply.The output voltage of this power supply circuit can be adjust from 0V to 28V DC, while the current output is static the rang is about 6A up to 8A.

AC to DC Schematic

1. Classic Plus and Minus DC Power Supply - produces both a positive 15v and a negative 15v from a 20vac wall adapter.
2. AC to DC Boost Converter with PFC - Implementation of a AC to DC Boost Converter with power factor correction.
3. Classic Linear 5v Supply Using 6.3vac Transformer - Circuit consists of an iron core transformer, a bridge rectifier, a filter capacitor and a voltage regulator.
4. AC-to-DC converter circuit utilizing IGBTs - AC-to-DC converter furnishing a regulated DC-output voltage from an AC-input supply voltage
5. Non-isolated Off-line AC to DC Power Supply - Efficient circuit can provide up to 100ma of a regulated 5 volts from an AC power.