Random circuits

Here are some of over 800 projects from our free circuit diagrams database. For more, try browsing categories menu on the left.

Cheap 12V to 220V Inverter

Even though today’s electrical appliances are increasingly often self-powered, especially the portable ones you carry around when camping or holidaying in summer, you do still sometimes need a source of 230 V AC - and while we’re about it, why not at a frequency close to that of the mains? As long as the power required from such a source remains relatively low - here we’ve chosen 30 VA - it’s very easy to build an inverter with simple, cheap components that many electronics hobbyists may even already have.... [read more]

Electronic Thermostat and Relay Circuit

Here is a simple thermostat circuit that can be used to control a relay and supply power to a small space heater through the relay contacts. The relay contacts should be rated above the current requirements for the heater.... [read more]

Dual-rail Variable DC Power Supply

This simple unit provides a dual-rail variable output ranging from ±2.5V to ±15Vdc with precise tracking of the positive and negative output voltages, still retaining the current limiting and short-proof capabilities of the "master" circuit. As the purpose of such a dual-rail design is to supply experimental or under-repair circuits, the maximum current output delivered was deliberately kept to about 500 - 600mA per rail, thus avoiding the use of expensive power transistors and complex circuitry.... [read more]

Loudspeaker Protection 2 for P.A output

The circuit protection output of power amplifiers and loudspeakers, dispose certain interesting elements, as the isolation of loudspeakers from the exit of amplifier, when is presented continuous voltage in his exit or when the temperature of heatsink, goes up excessively, providing simultaneously and time delay in the connection loudspeakers in the amplifier, so that we avoid pass in them, the known annoying noises from the charge - discharge of capacitors of supply.... [read more]

Moduler Preamplifier Circuit Diagram

To complement the 60 Watt MosFet Audio Amplifier a High Quality Preamplifier design was necessary. A discrete components topology, using + and - 24V supply rails was chosen, keeping the transistor count to the minimum, but still allowing low noise, very low distortion and high input overload margin. Obviously, the modules forming this preamplifier can be used in different combinations and drive different power amplifiers, provided the following stages present a reasonably high input impedance (i.e. higher than 10KOhm).... [read more]

Portable Headphone Amplifier

Can be directly connected to CD players, tuners and tape recorders. Tested with several headphone models of different impedance: 32, 100, 245, 300, 600 & 2000 Ohms. Schematic shows left channel only.... [read more]