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This circuit is made to be an alarm, both for home and handbags. If it is installed for home it will placed on door or windows, and if it is installed for bags or handbags it will placed in the bag. This circuit consists of a small magnet and a reed switch. If the magnet looses its contact with the reed switch, SW1 opens, the circuit starts oscillating and the loudspeaker emits a loud alarm sound.so this circuit suitable for use as an anti-theft alarm. This circuit uses A complementary transistor-pair which is wired as a high efficiency oscillator, directly driving a small loudspeaker. Low part-count and 3V battery supply enable a very compact construction. Notes : The loudspeaker’s dimensions are limited only by the box that contain it. An on-off switch is unnecessary because the stand-by current drawing is less than 20µA. Current consumption when the alarm is sounding is about 100mA. If the circuit is used as anti-bag-snatching, SW1 can be replaced by a 3.5mm mono Jack socket and the...

Here is a very easy build Electronic Circuit Project of magnetic field meter circuit. Using a pickup coil to drive an amplifier (IC3A-B-C-D), this meter circuit can be directly calibrated in field-intensi ty units. Magnetic Field Meter Circuit Diagram: R3/C3 and R12/C7 establish a frequency roll off that compensates for the pickup-coil sensitivity, and set a 20-kHz cut-off point. S2 is the range-select switch. Ll is an 18-turn 3` diameter coil. The frequency range is 50 Hz to 20 kHz and the range of measurement is 0.1 to 20 000 microTesiers (uT).

A magnetic stirrer uses a rotating magnetic field to mix fluid samples, such as buffers and media for growing bacteria. Since only a small magnet bar has to be put inside the sample/fluid, the risk of contamination is minimized. For protein purification, overnight sample dialysis steps often utilize magnetic stirrers. Below are beta release DIY instructions for a magnetic stirrer this summer, courtesy of Malcolm Watts and Massey University in New Zealand. The stirrer runs of off a battery and has multiple speed settings. [ ]