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This digital thermometer circuit diagram uses a common 1N4148 diode as the temperature sensor. The temperature coefficient of the diode, -2 mV / 0C is exploited for this application to create an accurate electronic thermometer. To display the measured temperature, a digital multimeter is used and so we can measure temperature values from -9.990C up to +99.90C.   Calibration of the digital thermometer To set the minimum level (00C), place the diode in a glass of water filled with crushed ice (check the temperature first with a normal thermometer) wait until the thermometer shows zero degrees centigrade. Set P1 so that the digital voltmeter will display 000 when the diode senses zero degree centigade. To set the maximum level (1000C), place the diode sensor into a boiling water and adjust P2 so that the digital meter exactly displays 99.9. source [link] 

The author wanted a very cheap and simple alarm for some of his possessions, such as his electrically assisted bicycle. This alarm is based on a cheap window alarm, which has a time-switch added to it with a 1-minute time-out. The output  pulse of the 555 replaces the reed switch in the window alarm. The 555 is triggered by a sensor mounted near the front  wheel, in combination with a magnet that is mounted on the spokes. This sensor and the magnet were taken from a cheap bicycle computer.  Cheap Bicycle Alarm Schematics Circuit diagram : Cheap Bicycle Alarm Circuit Diagram The front wheel of the bicycle is kept unlocked, so that the reed  switch closes momentarily when the wheel turns. This  triggers the 555, which in turn activates the window alarm. The circuit around the 555 takes very little current and can  be powered by the batteries in the window alarm.  There  is just enough room  left inside the enclosure of the window  alarm t...

Do not misunderstand, this series is one of several series of power amplifiers that have output / low output power. This amplifier output is only possess more or less 4Watt. Or 2 X 2Watt stereo power amplifier. Minimum required voltage is not less than 3 volts and a maximum voltage of no more than 14 volts, and voltage must be rectified and filtered to obtain the maximum of the processed audio. Component List : R1 = 2,7R R2 = 2,7R C1 = 1uF C2 = 1uF C3 = 100uF C4 = 220uF C5 = 100uF C6 = 100uF C7 = 220uF C8 = 0.1uF C9 = 0.1uF C10 = 470uF C11 = 470uF U1 = ULN3750B

The author wanted a very cheap and simple alarm for some of his possessions, such as his electrically assisted bicycle. This alarm is based on a cheap window alarm, which has a time-switch added to it with a 1-minute time-out. The output  pulse of the 555 replaces the reed switch in the window alarm. The 555 is triggered by a sensor mounted near the front  wheel, in combination with a magnet that is mounted on the spokes. This sensor and the magnet were taken from a cheap bicycle computer. Circuit diagram : Cheap Bicycle Alarm Circuit Diagram The front wheel of the bicycle is kept unlocked, so that the reed  switch closes momentarily when the wheel turns. This  triggers the 555, which in turn activates the window alarm. The circuit around the 555 takes very little current and can  be powered by the batteries in the window alarm.  There  is just enough room  left inside the enclosure of the window  alarm to mount the time-switch inside it. The result is a very cheap, compact devic...

The TDA9302H is a monolithic integrated circuit in HEPTAWATTTM package. This is a high efficiency power amplifier for direct drive vertical rolls from the yokes of TV . This is intended to be used in Color and B & W television as well as in monitors and displays . Pin Connection : Supply Voltage pin 2                                35V Flyback peak voltage                               60V Voltage at pin 3                                        +Vs Amplifier Input Voltage                           -0.5V Deflection Output Current       ...