Welcome!

Headphone Amplifier... [read more]

This timer was designed mainly to switch off a portable radio after some time: in this way, one can fall asleep on the sand or on a hammock, resting assured that the receiver will switch off automatically after some time, saving battery costs.... [read more]

Most off-the-shelf car battery chargers cannot not be left connected to the battery for long periods of time as over-charging and consequent battery damage will occur. This add-on circuit is placed in series with the battery being charged and is powered by the battery itself. In effect, the circuit uses a high-current Mosfet to control the charging current and it turns off when the battery voltage reaches a preset threshold. Power for the circuit is fed from the battery to 3-terminal regulator REG1 which provides 8V.... [read more]

Stethoscopes are not only useful for doctors, but home mechanics, exterminators, spying and any number of other uses. Standard stethoscopes provide no amplification which limits their use. This circuit uses op-amps to greatly amplify a standard stethoscope, and includes a low pass filter to remove background noise.... [read more]

This circuit should only be used with the solenoid type chime doorbells, the electronic type that play tunes will not work here.... [read more]

This circuit was developed to charge the Lithium-Polymer cells used in a model aircraft. Lithium-Polymer cells are incredibly lightweight compared to Ni-cad battery packs of the same voltage and amp-hour rating. Their only drawback is that they require a rigid charge and discharge regime to achieve maximum life.... [read more]