Welcome!

This device is designed to be a simple, inexpensive ‘comparator’, intended for use in a solar cell power supply setup where a quick ‘too low’ or ‘just right’ voltage indicator is needed. The circuit consists only of one 5V regulator, two transistors, two LEDs, five resistors, two capacitors, and one small battery. Although a 4-V battery is indicated, 4.5 V (3 alkalines in series) or 3.6 V (3 NiCd cells in series) will also work.... [read more]

This is a small electronic switch that connects a battery to the equipment for a certain amount of time when a push-button is momentarily pressed. And we have also taken the ambient light level into account; when it is dark you won’t be able to read the display so it is only logical to turn the switch off, even if the time delay hasn’t passed yet. The circuit is quite straightforward. For the actual switch we’re using a well-known MOSFET, the BS170.... [read more]

Capacitive touch sensors are based on the electrical capacitance of the human body. When, for example, a finger comes close to the sensor, it creates a capacitance to Earth with a value of 30 to 100 pF. This effect can be used for proximity detection and touch-controlled switching. Capacitive switches have clear advantages compared to other types of touch switches (for example 50 Hz or 60 Hz detection or resistance detection), but are often more complex to implement.... [read more]

In recent years, following CD's introduction, vinyl recordings are almost disappeared. Nevertheless, a phono preamplifier is still useful for listening old vinyl discs from a well preserved collection. This simple but efficient circuit devised for cheap moving-magnet cartridges, can be used in connection with the audio power amplifiers shown in these web pages, featuring low noise, good RIAA frequency response curve, low distortion and good high frequency transients behavior due to passive equalization in the 1 to 20 KHz range.... [read more]

This is a combination digital clock timer and solar panel charge controller used to maintain a deep cycle battery from a solar panel. The timer output is used to control a 12 volt load for a 32 minute time interval each day.... [read more]

The two circuits illustrate opening a relay contact a short time after the ignition or ligh switch is turned off. The capacitor is charged and the relay is closed when the voltage at the diode anode rises to +12 volts.... [read more]