220V AC Lamp Toggle Switch

Compact, transformerless circuitry No relays employed

Due to the low current drawing, the circuit can be supplied from 230Vac mains without a transformer. Supply voltage is reduced to 12Vdc by means of C1 reactance, a two diode rectifier cell D1 & D2 and Zener diode D3. IC1A, IC1B, R2, R3 and C3 form a reliable bounce-free toggle switch operated by P1. R4 and C4, wired to pin #6 of IC1B reset the circuit (lamp off) when power supply is applied. IC1C and IC1D wired in parallel act as a buffer, driving the Gate of the Triac through R5.


Circuit diagram:

220V AC Lamp Toggle Switch Circuit Diagram

Emergency Light and Alarm

This Emergency Light and Alarm circuit comes with 4 switchable options. It is permanently plugged into a mains socket and NI-CD batteries are trickle-charged. When a power outage occurs, the lamp automatically illuminates. Instead of illuminating a lamp, an alarm sounder can be chosen. When power supply is restored, the lamp or the alarm is switched-off. A switch provides a "latch-up" function, in order to extend lamp or alarm operation even when power is restored.


Circuit Diagram:

Emergency Light and Alarm Circuit Digram

25 Watt Audio Power Amplifier

This is a 25 Watt basic power amp that was designed to be (relatively) easy to build at a reasonable cost. It has better performance than the standard STK module amps that are used in practically every mass market stereo receiver manufactured today. This high quality simple design doesn't need a preamplifier

Circuit diagram:

25 Watt Audio Amplifier Circuit Diagram

Fire Alarm Using Thermistor

This small and simple fire alarm circuit uses thermistor as the heat sensor. When temperature increases, its resistance decreases, and vice versa. At normal temperature, the resistance of the Thermistor (TH1) is approximately 10 kilo-ohms, which reduces to a few ohms as the temperature increases beyond 100 C. The circuit uses readily available components and can be easily constructed on any general-purpose PCB. You can used this circuit as Home-Security purpose.


Circuit Diagram:

Fire Alarm Circuit Diagram

Low Cost Hearing Aid

Small and portable hearing aid for old men and old women.  

This low-cost, general-purpose electronic hearing aid works off 3V DC (2x1.5V battery). The circuit can be easily assembled on a veroboard. For easy assembling and maintenance, use an 8-pin DIP IC socket for TDA2822M.

Circuit Diagrams:

A Low Cost hearing Aid Schematic

Car-Bulb Flasher

Suitable for alerting purpose, Drives 12v Car bulbs
This astonishingly simple circuit allows one or two powerful 12V 21W car bulbs to be driven in flashing mode by means of a power MosFet. Devices of this kind are particularly suited for road, traffic and yard alerts and in all cases where mains supply are not available but a powerful flashing light are yet necessary.

Circuit Diagram:

Mobile Phone Battery Charger

Small and portable unit, Can be assembled on veroboard
Mobile phone chargers available in the market are quite expensive. The circuit presented here comes as a low-cost alternative to charge mobile telephones/battery packs with a rating of 7.2 volts, such as Nokia 6110/6150.


Circuit diagram:

Mobile Phone Battery Charger Circuit Diagram