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Newly Updated Circuit Projects:

Cell Phone Emergency Charger Pack using Ni-Cd Batteries

Last Updated on May 17, 2026 by Swagatam 62 Comments

4aaacellholder

In this post  I have explained the construction of a simple emergency charger pack using Nicket Cadmium (Ni-Cd) batteries for your cellphones and smart phones for emergency charging of your cellphone, so that next time you are never stuck on a highway with a full discharged dead cellphone battery. Circuit Concept It often happens, our […]

Filed Under: Battery Charger Circuits Tagged With: Batteries, Cell, Charger, Emergency, Pack, Phone

How to Switch Two Batteries Manually using Opto Coupler

Last Updated on May 17, 2026 by Swagatam 27 Comments

batterychangeoverrelaycircuit

The following article explaining a dual battery changeover relay circuit was requested by Mr.Raja so that it could become possible to switch between his old and new inverter batteries automatically, eliminating manual interventions. Let’s read it in details. Technical Specifications “I bought a new 12v 110 Ah lead acid battery for the dc home lighting system. I had another  12v […]

Filed Under: Battery Charger Circuits Tagged With: Batteries, Coupler, Manually, Opto, Switch

Making a Multi-function Water Level Controller Circuit

Last Updated on June 12, 2019 by Swagatam 53 Comments

waterlevelcontrollertimercircuit

The following multi-function water level controller circuit post is based on the suggestions expressed by Mr. Usman. I have explained more about the requested modifications and the circuit details. The Circuit Suggestion: The concept of this circuit looks good. May I suggest a couple of other desirable features? 1) To protect the motor from potential overheating (or […]

Filed Under: Water Controller Tagged With: Controller, function, Level, Making, Multi, Water

Simplest AM Radio Circuit

Last Updated on May 15, 2026 by Swagatam 173 Comments

Antenna Coil

The following circuit was taken from an old electronic book, it is indeed a very nice little two transistor radio receiver circuit which utilizes very few components yet is able to produce output over a loudspeaker and not just over headphones. Circuit Operation As can be seen in the given circuit diagram, the design is […]

Filed Under: Audio and Amplifier Projects Tagged With: AM, Radio, Simplest

Make this Musical Greeting Card Circuit

Last Updated on May 15, 2026 by Swagatam 18 Comments

simplemusicalgreetingcardcircuit

The presented circuit of a musical greeting card circuit was requested by one of the keen readers of this blog, so I designed this interesting little circuit, which is simple and easily gets embedded inside any standard greeting card fold. Looking at the given circuit diagram, we see a design consisting of a very few number of components, rigged […]

Filed Under: Audio and Amplifier Projects Tagged With: Card, Greeting, Musical

Designing a Grid-Tie Inverter Circuit

Last Updated on August 3, 2020 by Swagatam

gridtieinvertercircuitsdiagram

A grid tie inverter works quite like a conventional inverter, however the power output from such inverter is fed and tied with the AC mains from the utility grid supply. As long as the mains AC supply is present, the inverter contributes its power to the existing grid mains supply, and stops the process when […]

Filed Under: Inverter Circuits Tagged With: Designing, Grid, Inverter

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