PIR Motion Detector

A very simple pir motion detector circuit can be designed using this diagram .This pir motion detector circuit project use a PIR sensor , operational amplifiers a sound generator circuit and some others common electronic components .The op-amp IC1D shapes the frequency response to amplify those frequencies produced when motion is detected and rejects all others, such as those due to noise or slow temperature changes.As motion is detected, the voltage at the output will change and trigger either IC1C or IC1B.The op-amps IC1A, IC1B and IC1C are configured as voltage comparators.

When IC1D outputs a voltage lower than 1.41V, it will force pin 2 of IC1 high.When IC1D outputs a voltage higher than 1.67V, it forces pin 8 and pin 2 of IC1 to go high. A high in with one of these cases causes the output to go low and allows C9 to discharge through IC1A. The discharging of C9 will pull pin 6 of IC2 low and trigger the sound generator.The Passive Infrared Sensor (PIR) used in this alarm circuit can be LHI-954 , KDS245 or other similar type .As sound generator you can use a HT2810 or HT2812 sound generator integrated circuit .This motion detector alarm circuit requires two DC voltage 5 volts for almost all power connections and 9 volts for the sound generator circuit .

Home Made Metal Detector

This homemade metal detector circuit will help you find objects composed of materials with relatively high magnetic permeability. It is not suitable for buried coins discovery that is not sensitive enough but you can detect pirates treasures!

The metal detector is powered by 2 x 9V batteries, each of it charges with 15mA. L1 detector coil is part of the sinusoidal oscillator built around transistor T1. Normally, the center frequency of the voltage controlled oscillator (VCO) from the PLL loop that is contained in IC1 is equal to the oscillation frequency of T1. This changes when entering a metallic object (ferrous or nonferrous) in the field induced by L1. S1 is a miniature 2-pole switch.

Meter needle deviation is a measure of frequency change, since the direction of deviation depends on the type of material detected by the coil.
The meter tool used for this homemade metal detector is zero as central, +-50µA.

Metal detector circuit schematic

Coil L1 consists of 40 turns of enamelled copper wire, wound on a plastic template with a diameter of about 10 cm. Inductance thus obtained ensure the functioning of the oscillator at a frequency approximately equal to the VCO included in the PLL loop.

Use an oscilloscope to check that pin 2 of IC1 delivers sinusoidal signal with frequency about 75 kHz. Adjust P1 so that fronts rectangular signal from pin 4 to coincide with the peaks of the sinusoidal signal from pin 2. Then, adjust P2 in order to obtain 0 on the meter. Since the neutral zero setting “runs” with the battery’s decreasing voltage it will be necessary to restore it (zero balancing) from time to time during use of the metal detector.