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Unlike many units, this battery charger continuously charges at maximum current, tapering off only near full battery voltage. In this unit, the full load current of the supply transformer/rectifier section was 4.4A. It tapers off to 4A at 13.5V, 3A at 14.0V, 2A at 14.5V and 0A at 15.0V.... [read more]

This device is a simple timer, allowing to keep on the headlights of your vehicle for about 1min. and 30sec., e.g. when accessing some dark place, without the necessity of coming back to switch-off the lights.... [read more]

A simple STEREO amplifier, with minimal external components. It use one only opamp., that is capable to give output power 2X5W in the 4 ohms, with distortion 0.5%.... [read more]

This is a programmable clock timer circuit that uses individual LEDs to indicate hours and minutes. 12 LEDs can be arranged in a circle to represent the 12 hours of a clock face and an additional 12 LEDs can be arranged in an outer circle to indicate 5 minute intervals within the hour. 4 additional LEDs are used to indicate 1 to 4 minutes of time within each 5 minute interval.... [read more]

Here's a circuit that takes advantage of the photo-voltaic voltage of an ordinary LED. The LED voltage is buffered by a junction FET transistor and then applied to the inverting input of an op-amp with a gain of about 20. This produces a change of about 5 volts at the output from darkness to bright light. The 100K potentiometer can be set so that the output is around 7 volts in darkness and falls to about 2 volts in bright light.... [read more]

If you are the proud owner of an old oscilloscope tube, you may be interested in using it once more for its original purpose. All you need are the right voltages on the right pins: in practice you may need to peer closely inside to find out which pins on the base correspond to the acceleration and deflection electrodes, in particular if there is no part number to be seen on the tube. The tube we had for experimental purposes was a 7 cm model of unknown provenance.... [read more]