Random circuits

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Bench Amplifier

A small 325mW amplifier with a voltage gain of 200 that can be used as a bench amplifier, signal tracer or used to amplify the output from personal radios, etc.... [read more]

Protection For Telephone Line

A long time ago when telephones were so simple almost nothing could go amiss from an electrical point of view, Telecom operators installed surge protection on all telephone lines exposed to storm risks. Paradoxically, now that we are hooking up delicate and expensive equipment such as telephones filled with electronics, fax machines, (A)DSL modems, etc., this protection has disappeared.... [read more]

Dome Lamp Dimmer

There are times when a little light inside the car would greatly assist one of the passengers but the dome light is too bright for safe driving.... [read more]

Symmetrical from a single voltage supply

Many times we needed symmetric voltage, but we do not have the possibility him of taking immediately, from a existing supply. Then it will be supposed him we create from the existing single.... [read more]

Automatic Low-Power Emergancy Light

Here is a white-LED-based emergency light that offers the following advantages. 1-It is highly bright due to the use of white LEDs. 2-The light turns on automatically when mains supply fails, and turns off when mains power resumes. 3-It has its own battery charger. When the battery is fully charged, charging stops automatically. The charger power supply section is built around 3-terminal adjustable regulator IC LM317 (IC1), while the LED driver section is built around transistor BD140 (Q2).... [read more]

Static Electricity / Negative Ion Detector

This circuit relies upon the extra high input impedance of a FET, and also demonstrates the gate terminals sensitivity to changes in voltage. The gate terminal here is left open circuit, connected only to the "probe" this being just a few inches of bare copper wire.... [read more]