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Temperature-controlled Fan
Temperature-controlled Fan
October 25, 2010

This circuit adopt a rather old design technique as its purpose is to vary the speed of a fan related to temperature with a minimum parts counting and avoiding the use of special-purpose ICs, often... [more]

Geomagnetic field detector
Geomagnetic field detector
October 23, 2010

This basic oscillator will detect the Earth magnetic field. The ferrite rod and coil are taken from an old Medium Wave receiver and a small magnet is glued at one end. [more]

Frost Alarm
Frost Alarm
October 23, 2010

The thermistor used has a resistance of 15k at 25 degrees and 45k at 0 degrees celsius. [more]

Fridge door Alarm
Fridge door Alarm
October 23, 2010

This circuit, enclosed in a small box, is placed in the fridge near the lamp (if any) or the opening. [more]

Heating System Thermostat
Heating System Thermostat
October 23, 2010

This circuit is intended to control a heating system or central heating plan, keeping constant indoor temperature in spite of wide range changes in the outdoor one. [more]

Live-line Detector
Live-line Detector
October 16, 2010

If the unit is brought close to a live conductor (insulated, and even buried in plaster) capacitive coupling between the live conductor and the probe clocks the counter, and causes the LED to flash 5... [more]

Metal Detector
Metal Detector
October 13, 2010

The circuit described here is that of a metal detector. The opera- tion of the circuit is based on superheterodyning principle which is commonly used in superhet receivers. The circuit utilises two RF oscillators. [more]

Temperature Monitor
Temperature Monitor
October 12, 2010

Using a thermistor in the position shown makes a heat activated sensor. A change in temperature will alter the output of the opamp and energize the relay and light the LED. Swapping the position of... [more]

Voice activated switch
Voice activated switch
October 5, 2010

This circuit uses an MC2830 to form a voice activated switch ( VOX ). A traditional VOX circuit is unable to distinguish between voice and noise in the incoming signal. In a noisy environment, the... [more]

Voltage Monitor
Voltage Monitor
October 5, 2010

When the input voltage is 0 the LED glows. The LED stops glowing when the voltage rises to the level determined by R2. Reverse + and - pins to reverse operating mode. To set voltage... [more]



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